Flashcards in Mesenchymal Tumours and Lymphoma Deck (28)
What are mesenchymal tumors?
Practically, they can be thought of as non-epithelial, non-melanocytic, non-lymphomatous skin tumors.
What are some of the types of mesenchymal tumors of the skin?
- tumors of fat
- tumors of fibrous tissue
- tumors of blood vessels and lymphatics
- tumors of muscle
- tumors with nerve sheath differentiation
What are malignant mesenchymal tumors called?
Describe benign tumors of fat.
- age 40+
- associated with obesity
- may be very large
- bright yellow homogenous fat with fine fibrous capsule and trabeculae
- greasy cut surface
- composed of mature adipocytes with uniform nuclei resembling normal white fat
- small amounts of fibrous tissue
What are the variants of lipoma?
These are benign tumors with similar macroscopic appearance but variable microscopic appearance.
- spindle cell lipoma
- chondroid lipoma
- pleomorphic lipoma
- angiolipoma - capillaries more prominent
Describe a malignant fat tumor.
3 main types:
a) atypical lipotamous tumour/well differentiated liposarcoma
b) myxoid/round cell liposarcoma
c) pleomorphic liposarcoma
Deep soft tissue
What is a dedifferentiated liposarcoma?
A biphasic tumor that includes an undifferentiated sarcomatous component.
What would MDM2 genetic amplification indicate?
What are some of the tumors of fibrous tissue?
b) Defmatofibrosarcoma protuberans (DFSP)
c) Atypical Fibroxanthoma (AFX)
- common site: legs of women 20-50
- recurrence not common
- tumor is composed of fibroblastic and histiocytic cells arranged in sheets or intersecting fascicles
- mixed population of cells – inflammatory cells consisting of lymphocytes, plasma cells and foamy histiocytes are also seen
- the stroma contains delicate collagen fibers in between cells
- mitotic activity not increased
- cytologic atypia absent
- no sharply defined borders
- usually show entrapment of surrounding dermal collagen
- overlying epithelial hyperplasia and hyperpigmentation
- well differentiated primary fibrosarcoma of the skin
- slow growing, can be locally aggressive and recur, but rarely metastasize
- firm, solid nodules mostly found on trunk
- composed of fibroblasts arranged radially in a stroriform patter (irregular pattern denoting a straw mat)
- mitoses present
- often show deep extendion into subcutaneous fat
- lace-like pattern
What are the key differences between Dermatofibroma and DFSP?
- the deep margin of DF usually shows limited infiltration into subcut tissues, whereas DFSP has more extensive infiltration.
- DSFP has more homogenous population of tumor cells, lacks inflammatory cells, foamy histiocytes and giant cells
- Stratiform pattern more pronounced in DFSP
- Mitotic activity increased in DFSP
- DF = factor 13a positive
- DFSP = CD34 positive
- generally rapidly growing nodular lesions in sun exposed areas of older patients
- rapid growth
- usually polypoid without ulceration.
- local excisions usually curative and recurrence is rare
- composed of atypical, pleomorphic spindle cells
- storiform or fascicle pattern
- abundant mitoses, but some mitotic figures atypical
- use immunohistochemistry to exclude melanoma, spindled squamous cell carcinoma or leiomyosarcoma. AFX will be negative for S-100, melan A, desmin and cytokeratins.
- overlying epidermis uninvolved
What are some of the tumors of histiocytes?
a) Juvenile Xanthogranuloma (JXG)
b) Fibroepithelial polyp/skin tag/acrochordon
- cutaneous histiocytic lesion usually seen in infancy and childhood
- most patients develop lesions by 6 months
- excellent prognosis – most regress spontaneously
- yellow or brown
- composed of sheets of histiocytes (eosinophilic cytoplasm) in dermis and extending to the flattened epidermis
- hallmark = touton giant cell
- inflammatory cells found in moderate numbers
Describe Fibroepithelial polyp/skin tag/acrochordon.
- middle aged and older people – trunk, face and interigous areas
- soft flesh coloured tumor attached to skin by a slender stalk
- fibrovascular cored covered in squamous epithelium
Name and describe a benign tumor of smooth muscle.
Leiomyoma = benign
Subtypes based on location:
- nipple or scrotum
- pilar leiomyoma
- intersecting fascicles
- cigar shaped nuclei
- no atypia
- no mitotic activity
- no necrosis
Name and describe a malignant tumor of smooth muscle.
Leiomyosarcoma = malignant
- arise from pilar muscles or genital smooth muscles
- middle aged males
- metastasis rare
- arise from vascular smooth muscle
- greater tendency for metastasis
Compared to leiomyoma:
- more cellular
- cytological atypia
Name and describe a benign tumor of blood vessels.
a) capillary Haemangiomas – thin walled capillaries
b) juvenile Haemangiomas
c) cavernous Haemangiomas – large, dilated vascular channels
d) lobular capillary Haemangiomas (‘pyogenic granuloma’)
– polypoid, often ulcerate and bleed
- will look like lobulated polyp, capillary sized vessels
Name 2 malignant tumors of blood vessels.
2. Kaposi Sarcoma
- head and neck in eldery
- associated with chronic lymphedema
- post radiation therapy
- slow growing but highly aggressive
- metastasize to regional lymph nodes and organ
Describe Kaposi Sarcoma.
- vascular neoplasm caused by HHV8 and highly associated with AIDS
- Four forms:
o Classic (older men)
o Endemic African
- Cutaneous lesions progress from patched to plaques to nodular tumors
- spindle cells forming slits with extravasated RBCs
- hemosiderin laden macrophages
- minimal atypia
List 2 benign neural tumours.
1. Neurofibroma (nerve sheath)
2. Neuroma (nerve fibers and schwann cells)
Describe a neurofibroma.
- benign nerve sheath tumour
- mixture of schwann cells, perineural cells, fibroblasts, mast cells
- sporadic or related to neurofibromatosis
- 3 growth patterns
o superficial cutaneous neurofibroma - pedunculated
o diffuse neurofibroma – plaque like elevation of skin
o plexiform neurofibroma – nerve roots or large nerves
Describe a neuroma.
- benign non neoplastic overgrowth of nerve fibers and schwann cells
- usually post traumatic
- common subtypes:
o amputation or traumatic neuroma
o morton neuroma
Histology of amputation neuroma:
- irregular organization of nerve fibers immersed in scar tissue
How are lymphomas of the skin divided? Give two examples.
Divided loosely into B cell and T cell proliferation.
Mycosis fungoides = a cutaneous T cell Lymphoma
Primary Cutaneous Follicle Centre Cell Lymphoma = a cutaneous B cell lymphoma
Describe Mycosis fungoides.
- a cutaneous T cell Lymphoma
- elderly or adults
- skin-homing CD4+ T helper cells
- progression: patch, plaque, nodule/tumor
- often misdiagnosed early as eczema
- usually remains localized to skin for many years, but may evolve into generalized lymphoma
- may look similar to dermatitis – increased lymphocytes
- neoplastic lymphocytes form a band-like zone in upper dermis
- convoluted nuclear membrane – this would be unusual for dermatitis
Describe Primary Cutaneous Follicle Centre Cell Lymphoma.
- presents with solitary or localized skin lesions on the scalp, forehead or trunk
- erythematous plaques or nodules
- nodular diffuse pattern