122: Lipogenic Tumors Flashcards
(117 cards)
1
Q
What is the most likely diagnosis for a 45-year-old male with a painless, slowly growing mass on his upper back?
A
The most likely diagnosis is a classical subcutaneous lipoma, which is a benign mesenchymal neoplasm composed of mature adipocytes with thin fibrous septa.
2
Q
What is the diagnosis for a patient with multiple painful subcutaneous lesions on the forearm showing mature adipocytes and fibrin thrombi?
A
The diagnosis is angiolipoma, a benign mesenchymal tumor characterized by painful subcutaneous lesions with fibrin thrombi in capillaries.
3
Q
What is the diagnosis for a 10-year-old boy with a painless, slowly growing lesion on his trunk showing lobulated tumor with lipogenic cells?
A
The diagnosis is lipoblastoma, a rare benign neoplasm of embryonal white fat seen predominantly in children.
4
Q
What condition is likely for a middle-aged man of Mediterranean origin with symmetric fat deposits around his neck and shoulders?
A
The patient likely has symmetric lipomatosis (Madelung disease), which is characterized by symmetric fat deposits in the neck and shoulder region.
5
Q
What is the likely diagnosis for a patient with a history of hormonal therapy and diffuse fat accumulation?
A
The likely diagnosis is steroid lipomatosis, which is associated with hormonal therapy or increased endogenous adrenocortical steroids.
6
Q
What is the diagnosis for a child with plaques and papules on the buttocks, showing mature adipose tissue replacing the dermis?
A
The diagnosis is nevus lipomatosis superficialis, a rare connective tissue nevus affecting children and young adults.
7
Q
What is the diagnosis for a 60-year-old male with a painless, mobile tumor on the posterior neck showing mature adipocytes and spindle cells?
A
The diagnosis is spindle-cell lipoma, a benign neoplasm commonly seen in elderly males.
8
Q
What is the diagnosis for a 35-year-old female with a deep-seated, painless mass in the proximal extremity showing multivacuolated lipoblasts?
A
The diagnosis is chondroid lipoma, a rare benign lipogenic neoplasm.
9
Q
What is the diagnosis for a 50-year-old female with a large, painless mass in the retroperitoneum composed of smooth muscle cells and mature fat?
A
The diagnosis is myolipoma, a rare benign neoplasm of soft tissues.
10
Q
What is the diagnosis for a young adult with a painless, slowly growing tumor in the thigh showing brown fat cells?
A
The diagnosis is hibernoma, a rare benign neoplasm of brown fat.
11
Q
What is the diagnosis for a 55-year-old male with a large, painless mass in the thigh showing mature adipocytes and hyperchromatic nuclei?
A
The diagnosis is atypical lipomatous tumor, a clinically aggressive lipogenic neoplasm.
12
Q
What is the diagnosis for a female presenting with a retroperitoneal mass showing smooth muscle cells and fat?
A
The diagnosis is myolipoma.
13
Q
What is the diagnosis for a young adult with a tumor in the thigh showing brown fat cells?
A
The diagnosis is hibernoma.
14
Q
What is the diagnosis for a patient with a large retroperitoneal mass showing a transition from atypical lipomatous tumor to high-grade pleomorphic sarcoma?
A
The diagnosis is dedifferentiated liposarcoma, characterized by a transition from atypical lipomatous tumor to nonlipogenic sarcoma.
15
Q
What is the diagnosis for a 30-year-old male with a painless mass in the thigh showing a myxoid stroma with mesenchymal cells?
A
The diagnosis is myxoid liposarcoma, a malignant lipogenic neoplasm.
16
Q
What is the diagnosis for an elderly male with a rapidly growing mass in the lower extremity showing pleomorphic lipoblasts?
A
The diagnosis is pleomorphic liposarcoma, a high-grade sarcoma with pleomorphic lipoblasts.
17
Q
What is the diagnosis for a patient with a painless, slowly growing mass in the subcutaneous tissue showing mature adipocytes?
A
The diagnosis is a classical lipoma, a benign mesenchymal neoplasm.
18
Q
What is the diagnosis for a patient with a painful subcutaneous lesion on the forearm showing increased blood vessels and fibrin thrombi?
A
The diagnosis is angiolipoma, characterized by painful lesions with increased blood vessels and fibrin thrombi.
19
Q
What is the diagnosis for a child with a painless, lobulated tumor on the trunk showing immature lipogenic cells?
A
The diagnosis is lipoblastoma, a benign neoplasm of embryonal white fat.
20
Q
What condition is likely for a man with symmetric fat deposits in the neck?
A
The condition is symmetric lipomatosis (Madelung disease).
21
Q
What is the likely diagnosis for a patient on hormonal therapy presenting with fat accumulation?
A
The likely diagnosis is steroid lipomatosis.
22
Q
What is the diagnosis for a child with plaques on the buttocks showing adipose tissue replacing the dermis?
A
The diagnosis is nevus lipomatosis superficialis.
23
Q
What is the diagnosis for an elderly male with a tumor on the neck showing adipocytes and spindle cells?
A
The diagnosis is spindle-cell lipoma.
24
Q
What is the diagnosis for a female with a mass in the extremity showing adipocytes and a myxoid-chondroid stroma?
A
The diagnosis is chondroid lipoma.
25
What is the most common benign mesenchymal neoplasm in adults?
Lipoma is the most common benign mesenchymal neoplasm in adults.
26
What are the clinical features of lipomas?
Lipomas are characterized by a painless, slowly growing mass involving the subcutaneous tissue of the trunk, neck, or extremities; involvement of the hands and feet is uncommon.
27
What are the types of lipomas based on their location and characteristics?
1. **Superficial lipomas** - typically small, measuring less than 5 cm.
2. **Deep-seated intramuscular and intermuscular lipomas** - may reach a considerable size.
3. **Parosteal lipoma** - arises on the surface of bone.
4. **Lipoma arborescens** - represents a villous lipomatous proliferation of the synovial membrane.
28
What cytogenetic abnormalities are commonly associated with lipomas?
Common cytogenetic abnormalities in lipomas include:
| Abnormality Type | Description |
|------------------|-------------|
| Aberrations | Involving 12q13-15 |
| Rearrangements | Involving 6p21-23 |
| Deletions | Involving 13q |
29
What role does the HMGA2 gene play in lipomas?
The HMGA2 gene, localized at 12q14.3, plays an important role in the pathogenesis of some lipomas, and recombination of HMGA2 with several genes has been reported.
30
What are the histologic features of classical subcutaneously located lipomas?
Classical subcutaneously located lipomas are well-circumscribed, encapsulated, and lobulated lesions composed of mature adipocytes with thin and hypocellular fibrous septa containing thin-walled capillaries.
31
What are the histological characteristics of classical lipomas?
Classical lipomas show only slight variation in size and shape of adipocytes and exhibit no nuclear atypia. Immunohistochemically, tumor cells are negative for p16, MDM2, and CDK4.
32
What differentiates angiolipoma from atypical lipomatous tumors?
Angiolipoma is characterized by a variable increase in the number of blood vessels containing fibrin thrombi and often presents as painful multiple lesions. In contrast, atypical lipomatous tumors show striking variations in size and shape of lipogenic cells, with enlarged and hyperchromatic nuclei, and may contain atypical cells and lipoblasts.
33
What is the clinical course and treatment for classical lipomas?
Classical lipomas are entirely benign and recur only rarely. Surgical excision is curative, while intramuscular and intermuscular lipomas have a higher rate of local recurrences (up to 20%).
34
What is diffuse lipomatosis and its epidemiological characteristics?
Diffuse lipomatosis occurs predominantly in children and rarely in adults. It is characterized by a diffuse overgrowth of mature lipogenic tissue involving subcutaneous tissue and skeletal muscle of the trunk and extremities, with possible osseous involvement.
35
What is the common demographic for pelvic lipomatosis?
Pelvic lipomatosis is seen more frequently in **black males**.
36
What are the clinical features associated with symmetric lipomatosis (Madelung disease)?
Symmetric lipomatosis is characterized by:
1. Predilection for the **neck**, **shoulder**, and **proximal upper limbs**.
2. Common finding of **peripheral neuropathy** in patients.
3. In HIV-positive patients treated with protease inhibitors, there may be **lipodystrophy** with increased fat tissue at the neck, breast, and visceral organs.
37
What is the treatment of choice for lipomatosis?
The treatment of choice for lipomatosis is **palliative surgical excision** of the fat tissue. However, all forms of lipomatosis tend to recur, and massive accumulation of fat tissue may cause considerable clinical problems.
38
What is lipomatosis of nerve and its common associations?
Lipomatosis of nerve, also known as **fibrolipomatous hamartoma of nerve**, arises most frequently at **birth or in early childhood** and may be associated with **macrodactyly** of the digits innervated by the affected nerve.
39
What are the histologic features of lipomatosis of nerve?
The histologic features of lipomatosis of nerve include:
- **Epineurial and perineurial compartments** of the affected nerve are infiltrated by mature adipose tissue and collagenous fibrous tissue.
- **Concentric perineurial fibrosis** is present, and rarely, **metaplastic bone formation** has been reported.
40
What is the epidemiology of Nevus Lipomatosis Superficialis?
- Rare form of connective tissue nevus
- Usually affects children and young adults in the first decades of life with an equal gender distribution.
41
What are the clinical features of Nevus Lipomatosis Superficialis?
- Cases present as plaques, papules, or solitary lesions with a predilection for the buttocks, upper posterior thighs, and lumbar back.
- A generalized form is extremely rare.
- The lesions are unilateral, and sometimes a linear or zosteriform arrangement is noted.
42
What are the histologic features of Nevus Lipomatosis Superficialis?
- The ill-defined lesions are composed of mature adipose tissue that replaces the dermis.
- Thickening of collagen bundles, an increase of elastic fibers in deeper parts of the dermis, and an increase of fibroblasts may be seen.
- The overlying epidermis may show slight acanthosis and hyperpigmentation.
43
What is the differential diagnosis for Nevus Lipomatosis Superficialis?
Rare dermal spindle-cell lipoma is composed of mature adipose tissue associated with bland spindled tumor cells that stain positively for CD34, show loss of Rb-1 expression, and the often myxoid stroma contains hyalinized collagen fibers and mast cells.
44
What is the epidemiology of Lipoblastoma/Lipoblastomatosis?
- Rare, benign neoplasms of embryonal white fat.
- Predominantly in infants and young children, with a male predominance.
- Infrequently, tumors are congenital or occur in young adults.
45
What are the clinical features of Lipoblastoma/Lipoblastomatosis?
- Cases tend to occur on the trunk, at the extremities, and in the head and neck region.
- Visceral involvement and involvement of the retroperitoneum may occur.
46
What is the composition of roma?
Roma contains hyalinized collagen fibers and mast cells.
47
What are the clinical features of Lipoblastoma/Lipoblastomatosis?
- Cases tend to occur on the trunk, at the extremities, and in the head and neck region.
- Visceral involvement and involvement of the retroperitoneum, pelvis, mediastinum, and the abdominal cavity is rarely seen.
- Most cases present as painless, slowly growing lesions.
- Lipoblastoma is a well-circumscribed neoplasm, whereas lipoblastomatosis is characterized by infiltrative growth that often extends into deeper structures.
- A significant number of patients have disorders of the CNS, such as seizures, autism, developmental delay, congenital anomalies, and/or Sturge-Weber syndrome.
48
What are the histologic features of Lipoblastoma/Lipoblastomatosis?
Lipoblastoma represents a well-circumscribed, lobulated tumor composed of an admixture of mature and immature lipogenic cells separated by fibrovascular septa.
49
What is the etiology and pathogenesis of Lipoblastoma/Lipoblastomatosis?
Cytogenetically, the majority of analyzed cases show aberrations involving chromosome 8, and a recurrent translocation involving chromosome band 8q11-13 with rearrangements of the PLAG1 gene.
50
What are the characteristic histologic features of angiolipomas?
Angiolipomas are well-circumscribed, encapsulated nodular lesions composed of:
- Mature adipocytes
- A variable number of thin-walled capillaries, which may contain fibrin thrombi
- Stromal spindled cells
51
What is the clinical presentation of angiolipomas?
Angiolipomas tend to be multifocal and often present as:
- Painful and tender subcutaneous lesions
- Predominantly located on the forearm, followed by the trunk, upper arm, and legs
52
What is the epidemiology of angiolipomas?
Subcutaneous angiolomas are frequent mesenchymal tumors that occur predominantly in:
- Young males
- A familial incidence has been described.
53
What are the differential diagnoses for lipoblastoma/lipoblastomatosis?
The differential diagnoses for lipoblastoma/lipoblastomatosis include:
1. Myxoid liposarcoma
2. Lipoma
3. Lipofibromatosis
4. Hibernoma
5. Atypical lipomatous tumor
6. Rare lipoblastoma-like tumor of the vulva
54
What are the key diagnostic features that support the diagnosis of lipoblastoma/lipoblastomatosis?
Key diagnostic features include:
- Striking lobulation
- Lack of hyperchromatic nuclei
- Molecular changes that aid in diagnosis.
55
What are the clinical features of spindle-cell lipoma and pleomorphic lipoma?
- Both are usually asymptomatic, often longstanding, mobile tumors in the subcutaneous tissue.
- Commonly found on the posterior neck, shoulder, and upper back; less frequently on the face, oral cavity, and extremities.
- Purely dermal spindle-cell lipoma and pleomorphic lipoma show a broad anatomic distribution.
56
What is the etiology and pathogenesis of spindle-cell lipoma and pleomorphic lipoma?
- The karyotype is complex and frequently hypodiploid with frequent partial losses and few balanced rearrangements.
- Many cases show monosomy and partial losses involving chromosomes 13 and 16.
- These tumors likely represent points along a spectrum of a single clinicopathologic entity due to overlapping clinical, histologic, and molecular features.
57
How can cellular angiolipoma be differentiated from other vascular neoplasms?
- The presence of fibrin thrombi and clinical features are helpful in distinguishing angiolipoma from cases of lipoma with an increased number of vessels.
- Cellular angiolipoma must be distinguished from vascular neoplasms such as Kaposi sarcoma, kaposiform hemangioendothelioma, spindle-cell hemangioma, and angiosarcoma.
58
What are the histologic features of spindle-cell lipoma?
- Subcutaneous spindle-cell lipoma is encapsulated, composed of mature adipocytes and a variable number of cytologically bland spindled tumor cells in a collagenous and myxoid stroma.
- Contains blood vessels, hyalinized rope-like collagen fibers, and often mast cells; mitotic activity is virtually absent.
- Spindled cells can predominate, and cases without lipogenic cells may present significant diagnostic challenges.
59
What is the clinical course and prognosis of angiolipomas?
- The clinical behavior of angiolipomas is entirely benign.
- Simple resection is curative, indicating a favorable prognosis for patients with this condition.
60
What is the characteristic feature of pleomorphic lipoma?
The characteristic feature of pleomorphic lipoma is the additional presence of **multinucleated giant cells** with **radially arranged nuclei** (floret-like giant cells). Both low-fat and fat-free pleomorphic lipomas have been reported.
61
How do spindle-cell lipoma and pleomorphic lipoma differ from typical lipomas?
Spindle-cell lipoma and pleomorphic lipoma are **unencapsulated** and **infiltrative**, mimicking a more aggressive neoplasm, unlike typical lipomas which are usually encapsulated.
62
What immunohistochemical markers are associated with spindled cells and pleomorphic tumor giant cells?
Spindled cells and pleomorphic tumor giant cells stain positively for **CD34** and show loss of the expression of **Rb-1**. Very rarely, an expression of **desmin** and **S-100 protein** by spindled cells has been reported.
63
What distinguishes atypical lipomatous tumors from other lipomatous tumors?
Atypical lipomatous tumors show striking variation in size and shape of lipogenic cells, significant **atypia**, and the presence of enlarged and hyperchromatic nuclei. They may also exhibit focal nuclear expression of **MDM2** and **CDK4** amplification.
64
What is the clinical behavior of atypical spindle cell lipomatous tumors?
Atypical spindle cell lipomatous tumors and pleomorphic lipomatous tumors are locally aggressive neoplasms and show an **increased rate of local recurrences** compared to typical spindle-cell and pleomorphic lipomas, which are entirely benign.
65
What are the histological features of chondroid lipoma?
Chondroid lipoma is characterized by the presence of **adipocytes**, **lipoblasts**, and **small vacuolated cells** within a myxoid-encoded matrix, and tumor cells in chondroid lipoma are seen in cases of **chromo-11q13**.
66
What are the common clinical features of chondroid lipoma?
- Presents as a **painless**, **deep-seated mass**
- May show a **history of recent growth**
- Most frequently affected sites include the **proximal extremities** and **limb girdles**, but also the **trunk** and **head and neck region**
- Arises usually in **deep subcutaneous tissue**, **fascia**, and **skeletal muscle**.
67
What is the etiology and pathogenesis of chondroid lipoma?
- Confirmed **lipogenic differentiation** in cases of chondroid lipoma
- Spectrum of differentiation from **primitive mesenchymal cells** to **mature adipocytes**
- Involves a **balanced translocation** involving chromosomes 11 and 16, with a **C11orf95-MKL2 fusion gene**
- **Cyclin D1 (CCND1)** expression without abnormalities of the **CCND1 locus** has been reported.
68
What histologic features are characteristic of chondroid lipomas?
- Usually **deep-seated**, **well-circumscribed**, **encapsulated**, **nodular**, and **lobulated** neoplasms
- Composed of a variable admixture of **mature adipocytes**, **multivacuolated lipoblasts**, and **small round cells**
- Tumor cells set in a **myxoid-chondroid stroma**
- Positive **Alcian blue staining** indicates the presence of **sulfated chondroitin**
- Lesions may contain many **vessels**, and areas of **hemorrhage**, **fibrosis**, and **calcification** may be present.
69
What is the clinical course and treatment for chondroid lipoma?
- Chondroid lipoma is an **entirely benign lipogenic neoplasm**
- **Simple surgical excision** is curative
- **Local recurrences** are rare
- No reports of **malignant transformation** or **metastases** as of this writing.
70
What are the clinical features of myolipoma?
- Tends to occur in **deep soft tissue** of the **retroperitoneum**, **abdominal cavity**, and **inguinal region**
- Rarely involves **subcutaneous tissue** of the **extremities** and **trunk**
- Lesions may reach a **considerable size**, but are often found **incidentally**.
71
What genetic alterations have been reported in cases of myolipoma?
Alterations in the **HMGA2** gene have been reported, including a fusion of the **HMGA2** and **C9orf92** genes with t(9;12)(p22;q14).
72
What are the histologic features of myolipoma?
Myolipoma is characterized as a **well-circumscribed** or **encapsulated lesion** composed of fascicles of **cytologically bland smooth muscle cells** associated with a variable amount of **mature fat**. There is no cytologic atypia, mitoses, or thick-walled vessels present.
73
What is the differential diagnosis for myolipoma of soft tissues?
The differential diagnosis includes:
1. Atypical lipomatous tumor
2. Dedifferentiated liposarcoma
3. Well-differentiated leiomyosarcoma
4. Angiomyolipoma
74
What is the clinical course and treatment for myolipoma?
Despite its large size, myolipoma of soft tissues is an entirely **benign mesenchymal neoplasm**. The **complete excision** of the tumor is curative.
75
What is hibernoma and its epidemiology?
Hibernoma is a **rare neoplasm** that occurs predominantly in **young adults** and is rarely seen in children and the elderly. Males are slightly more frequently affected than females.
76
What are the clinical features of hibernoma?
Hibernoma is a **painless**, slowly growing, mobile tumor arising in the **subcutis** or in deep soft tissues. The most common anatomic site is the **thigh**, followed by the trunk, chest wall, shoulder area, upper extremity, and head and neck area. Rarely, it can arise intraabdominally, in the retroperitoneum, mediastinum, or intraosseous.
77
What are the histologic features of hibernoma?
Hibernomas are **well-circumscribed**, lobular neoplasms containing a **capillary network** and composed of a variable number of **brown fat cells** admixed with **white fat cells** and stromal cells. Typical hibernomas consist of large, polygonal, brown fat cells with **multivacuolation**, granular cytoplasm, and a small, centrally located nucleus.
78
What are the reported karyotypes of hibernoma?
The reported karyotypes of hibernoma appear to be more **complex** than those in other benign lipogenic neoplasms, with structural rearrangements involving chromosome band **11q13-21** detected.
79
What are the clinical features of atypical lipomatous tumors?
Atypical lipomatous tumors typically occur in deep soft tissues, with the subcutaneous tissue occasionally involved. The most affected sites include:
1. Musculature of the extremities (especially the thigh)
2. Retroperitoneum
3. Abdominal cavity
4. Groin
5. Paratesticular region
6. Mediastinum
Enlarging painless masses are common, and tumors may grow large before becoming symptomatic, particularly in retroperitoneal and intraabdominal locations.
80
What is the epidemiology of atypical lipomatous tumors?
Atypical lipomatous tumors represent the largest group of clinically aggressive lipogenic neoplasms. Key points include:
- Liposarcomas are the most frequent sarcomas in adults.
- Most cases occur in middle-aged adults, peaking in the sixth decade.
- Cases in children are extremely rare but have been documented.
81
What are the histologic features of atypical lipomatous tumors?
Atypical lipomatous tumors are characterized by:
- Large, well-circumscribed, and lobulated lesions.
- In retroperitoneal and intraabdominal locations, multiple discontinuous neoplasms may be present.
- Morphologically, they can be divided into three main subtypes:
1. **Adipocytic (lipoma-like) variant**: Composed of mature adipocytic cells with variations in size and shape, showing scattered enlarged and hyperchromatic nuclei.
2. **Eosinophilic variant**: Predominantly brown fat cells with eosinophilic and granular cytoplasm.
3. **Mixed subtype**: Intermediate between the two.
82
What is the clinical course and treatment for hibernoma?
Hibernoma is classified as an entirely benign lipogenic neoplasm. The clinical course is generally favorable, and the treatment involves:
1. **Complete excision**: This is curative for hibernoma, with a low risk of recurrence.
83
What are the differential diagnoses for atypical lipomatous tumors?
Differential diagnoses for atypical lipomatous tumors include:
- **Myxoid liposarcoma**: May present with scattered brown fat cells and hibernoma-like areas.
- **Granular cell tumor**: Needs to be distinguished from atypical lipomatous tumors.
- **Spindle-cell lipoma**: Another condition to consider in the differential diagnosis.
84
What are the characteristics of the second most frequent sclerosing variant of atypical lipomatous tumors?
The second most frequent sclerosing variant is characterized by:
- Presence of enlarged stromal cells with large and hyperchromatic nuclei.
- Set in a paucicellular, fibrillary, collagenous stroma.
- Scattered atypical lipogenic cells and lipoblasts.
85
What is the clinical behavior and prognosis of atypical lipomatous tumors dependent on?
The clinical behavior and prognosis of atypical lipomatous tumors are strongly dependent on:
1. The anatomic site of the tumor.
2. The depth of the tumor.
3. The size of the neoplasm.
86
How does the expression of p16, MDM2, and CDK4 help in the differential diagnosis of atypical lipomatous tumors?
Focal expression of **p16**, as well as nuclear staining for **MDM2** and/or **CDK4**, is helpful in differentiating atypical lipomatous tumors from other lipogenic and nonlipogenic lesions. However, very well-differentiated examples may not show these expressions, making **FISH analysis** useful in such cases.
87
What distinguishes typical lipoma from atypical lipomatous tumors?
Typical lipoma is distinguished from atypical lipomatous tumors by:
- Composed of mature adipocytes without nuclear atypia and lipoblasts.
- Does not stain positively for **p16**, **MDM2**, and **CDK4**.
88
What is the estimated rate of progression to dedifferentiated liposarcoma for atypical lipomatous tumors?
The estimated rate of progression to dedifferentiated liposarcoma for atypical lipomatous tumors is less than **2%**, with a mortality rate of virtually zero for cases arising at surgically amenable anatomic locations.
89
What are the histological features of atypical lipomatous tumors?
Composed of mature adipocytes without nuclear atypia and lipoblasts.
90
What immunohistochemical markers do atypical lipomatous tumors not stain positively for?
Does not stain positively for **p16**, **MDM2**, and **CDK4**.
91
What is the primary therapeutic approach for atypical lipomatous tumors in advanced cases?
Surgical excision is the primary therapeutic approach; adjuvant chemotherapy and radiotherapy may also be used in advanced cases.
92
What is the most common location for dedifferentiated liposarcoma?
The majority of dedifferentiated liposarcomas occur in the retroperitoneum, intraabdominal, and paratesticular locations.
93
What percentage of dedifferentiated liposarcoma cases develop as a de novo presentation?
Approximately 90% of cases develop as a de novo presentation, while 10% develop it in a local recurrence.
94
What are the histological features characteristic of dedifferentiated liposarcoma?
Histologically, dedifferentiated liposarcoma shows an abrupt or gradual transition from atypical lipomatous tumor features to nonlipogenic sarcoma areas, typically presenting as high-grade, undifferentiated, pleomorphic sarcoma.
95
What genetic alterations are associated with dedifferentiated liposarcoma?
Coamplification involving 1p32 and 6q23 with activation of the JUN and ASK2 genes has been reported in dedifferentiated liposarcoma.
96
What is the overall mortality rate of atypical lipomatous tumors in the retroperitoneum?
The overall mortality of atypical lipomatous tumors in the retroperitoneum is more than 80%.
97
What clinical feature is typically observed in cases of dedifferentiated liposarcoma?
Cases of dedifferentiated liposarcoma typically present as a large painless mass, often found in the retroperitoneum and intraabdominal locations by chance.
98
What is the significance of heterologous differentiation in dedifferentiated liposarcoma?
Heterologous differentiation is observed in approximately 10% of dedifferentiated liposarcoma cases, often showing myogenic or osteosarcomatous/chondrosarcomatous differentiation. This differentiation can impact the diagnosis and treatment approach.
99
What are the immunohistochemical markers associated with dedifferentiated liposarcoma?
Key immunohistochemical markers include strong expression of **p16**, **MDM2**, and **CDK4**, particularly in the nonlipogenic component. Additionally, myogenic differentiation is indicated by positive staining for markers such as **actin**, **desmin**, and **myogenin**.
100
What is the clinical course and prognosis of dedifferentiated liposarcoma?
Dedifferentiated liposarcoma is characterized by a protracted clinical course with a high risk for local recurrences and locally aggressive growth. The overall risk of distant metastatic spread is estimated at approximately 15% to 20%. Cases in the retroperitoneum and intraabdominal locations have a poorer prognosis.
101
What are the differential diagnoses for dedifferentiated liposarcoma?
The differential diagnosis for dedifferentiated liposarcoma includes:
| Tumor Type | Description |
|------------|-------------|
| Pleomorphic liposarcoma | A variant with significant cellular pleomorphism |
| Myxofibrosarcoma | A sarcoma with myxoid stroma and pleomorphic cells |
| GI stromal tumor | Tumors arising from the gastrointestinal tract |
| Leiomyosarcoma | Smooth muscle sarcoma |
| Rhabdomyosarcoma | Skeletal muscle sarcoma |
| Malignant solitary fibrous tumor | A rare tumor of mesenchymal origin |
| Rare fibrosarcoma | A type of sarcoma with fibrous tissue |
| Desmoid fibromatosis | A benign but aggressive fibrous tumor |
102
What treatment options are available for dedifferentiated liposarcoma?
The treatment of choice for dedifferentiated liposarcoma is **complete surgical removal**. However, this is often challenging in retroperitoneal and intraabdominal locations. New therapeutic options targeting gene products of chromosome 12 or inhibitors of the **Akt-mTOR** and **MAPK** pathways are being discussed for nonresectable cases.
103
What is the second most frequent variant of liposarcoma?
Myxoid liposarcoma is the second most frequent variant of liposarcoma, representing approximately 5% of all soft-tissue sarcomas in adults.
104
What are the common clinical features of myxoid liposarcoma?
Myxoid liposarcoma typically presents as a large, painless mass in deep soft tissues of the extremities, primarily on the thigh. It is rarely found in the subcutis or retroperitoneum.
105
What cytogenetic characteristics are associated with myxoid liposarcoma?
Myxoid liposarcoma is characterized by a recurrent translocation t(12;16)(q13;p11) with FUS-DDIT3 fusion in the majority of cases, and less commonly, a t(12;22)(q13:q12) with EWSR1-DDIT3 fusion.
106
What histologic features are observed in myxoid liposarcoma?
Histologically, myxoid liposarcoma consists of uniform, cytologically bland mesenchymal tumor cells and small lipoblasts in a prominent myxoid stroma, with microcystic spaces and thin-walled blood vessels. Well-differentiated neoplasms lack significant cytologic atypia, mitoses, and tumor necrosis.
107
What is the prognosis for patients with myxoid liposarcoma?
Myxoid liposarcoma tends to recur and may develop distant metastases in up to 40% of patients. Patients with multifocal disease at presentation have a poor prognosis, and adverse histologic features include round-cell differentiation, tumor necrosis, p53 overexpression, and CDKN2A aberrations.
108
What are the differential diagnoses for myxoid liposarcoma?
Differential diagnoses for myxoid liposarcoma include benign lesions such as lipoblastoma and chondroid lipoma, as well as malignant neoplasms like myxofibrosarcoma, low-grade fibromyxoid sarcoma, extraskeletal myxoid chondrosarcoma, and myxoid malignant melanoma.
109
What is pleomorphic liposarcoma and its epidemiological significance?
Pleomorphic liposarcoma represents the rarest sub-type of liposarcoma (5%) and arises predominantly in the elderly with a slight male predominance.
110
What are the common clinical features of pleomorphic liposarcoma?
Pleomorphic liposarcoma usually presents as a fast-growing neoplasm in deep soft tissues of the extremities, particularly in the lower extremities more than the upper. It rarely involves the trunk, retroperitoneum, abdominal cavity, head and neck region, and pelvis. A small but significant number of cases arise in subcutaneous tissues, while purely dermal neoplasms are exceedingly rare.
111
What are the histologic features of pleomorphic liposarcoma?
The histologic features include:
1. High-grade pleomorphic sarcoma characteristics, containing pleomorphic spindled cells and multinucleated tumor giant cells.
2. Presence of pleomorphic lipoblasts with enlarged, bizarre, hyperchromatic nuclei and cytoplasmic lipid droplets.
3. Morphologic similarities to intermediate-grade or high-grade myxofibrosarcoma with scattered pleomorphic lipoblasts.
4. The epithelioid variant shows large, densely packed tumor cells with eosinophilic cytoplasm resembling renal clear cell carcinoma or adrenal cortical carcinoma.
112
What is the etiology and pathogenesis of pleomorphic liposarcoma?
Cytogenetically, pleomorphic liposarcoma closely resembles other pleomorphic sarcomas and shows complex structural rearrangements. A small but significant number of cases reveal MDM2 and CDK4 amplifications, suggesting these neoplasms represent tumor progression from atypical lipomatous tumor or dedifferentiated liposarcoma.
113
What is characterized by a diffused overgrowth of mature adipose tissue infiltrating through pre-existing structures?
Lipomatosis
114
What is a growing mass with predilection of the hand and is a rare lesion seen in infants and children?
Lipomatosis of the nerve
115
What is the most common nerve involved in lipomatosis of the nerve?
Median nerve
116
What is a very rare benign mesenchymal neoplasm of deep soft tissue composed of an irregular mixture of mature adipocytes and smooth muscle cells?
Myolipoma
117
What is a benign neoplasm of brown fat?
Hibernoma
