Bone Flashcards

Question

Answer 1

ADAMANTINOMA * Peak incidence: 3rd decade of life * Most common site: tibia; intracortical in location * Low-grade neoplasm with epithelial differentiation * Four patterns * basaloid, often ameloblastoma-like * spindle cell * tubular * squamous * Unpredictable but usually indolent

Answer 2

GIANT CELL TUMOR OF BONE * Peak incidence: 3rd decade * Predilection for distal femur, proximal tibia * Epiphyseal in location * High rate of local recurrence following incomplete curettage * Can be locally destructive, necessitating surgical resection * Rarely metastasizes, usually to lung

Answer 3

CHORDOMA * Notochordal malignancy * Most common sites: sacrococcygeal, clivus, cervical vertebrae * Lobular growth pattern, syncytial clusters of cells with vacuolated cytoplasm – physaliferous cells * Clival lesions can have cartilaginous differentiation * Rarely can have dedifferentiation * Immunoreactivity for Brachyury, S100, pankeratin, EMA

Answer 4

EWING’S SARCOMA * Peak incidence: 2nd decade, predominantly males. * Predilection for metaphysis and diaphysis * Classic small round blue cell tumor * Immunoreactivty for CD99 and Fli-1 * t(11;22)(q24;q12)

Answer 5

ANEURYSMAL BONE CYST * 1st and 2nd decades * Predilection for distal femur, proximal tibia, spine * Histology * Blood-filled lakes with intervening fibrous septa * Within the septa are loosely-arranged spindle cells with variable number of giant cells * Osteoid and lace-like calcification present * Solid forms of ABC can occur and can be confused for malignancy, particularly osteosarcoma * Non-neoplastic; however, can see ABC-like area in primary bone tumors including chondroblastoma

Answer 6

Non-ossifying Fibroma or METAPHYSEAL FIBROUS DEFECT * Relatively common in children, often resolves spontaneously * Distal femur and proximal tibia. * Lesion usually aligned along long axis of bone * Histology * Spindle cells with storiform pattern * foamy histiocytes * multinucleated giant cells * hemosiderin deposition

Answer 7

BONE TUMORS OF THE ELDERLY * Metastatic carcinoma * Myeloma * Lymphoma

Answer 8

Unicameral bone cysts (UBC) or simple bone cysts (SBC) * common benign non-neoplastic lucent bony lesions * seen mainly in childhood and typically remain asymptomatic

Answer 9

Differential diagnosis of Ewing sarcoma * Lymphoma * Metastatic neuroblastoma * Mesenchymal chondrosarcoma * Embryonal rhabdomyosarcoma

Answer 10

Ewing sarcoma/PNET * t(11;22) (q24;q12) * fusion of the EWS and Fli-1 genes --\> EWS/Fli-1 fusion transcript * diagnostic of Ewing sarcoma/PNET * Stains * CD99+ \>90% * PAS & PAS-D+ for glycogen * Histology * Mitotic figures frequent (5-50/10 HPF) * Undifferentiated appearance * Small cells * Round to oval nuclei * Smooth nuclear membrane * Fine chromatin * Small nucleoli * Small amount of clear to amphophilic cytoplasm * Cell borders may be distinct * Differentiated appearance * Medium sized cells * Moderate sized nuclei with moderate atypia * Irregular nuclei * Small to medium sized nucleoli * Moderately abundant eosinophilic or amphophilic cytoplasm * Homer-Wright rosettes * Radiating fibrillar material surrounded by a ring of nuclei * Pseudorosettes * central blood vessel * Other patterns * alveolar or angiomatoid * Metaplastic cartilage or bone * Skeletal muscle in ectomesenchymoma variant

Answer 11

Embryonal rhabdomyosarcoma * uniform population of small round and spindle cells with frequent formation of pseudorosettes around small blood vessels and can mimic Ewing sarcoma/PNET. Although this tumor has many useful immunohistochemical markers (myosin, myogenin, sarcomeric actin, insulinlike growth factor II), it lacks a specific molecular marker, in contrast to Ewing sarcoma/PNET.

Answer 12

Myxoid Chondrosarcoma * rare variant of chondrosarcoma that may occur in soft tissue or bone * 40s to 50s * men are affected twice as often as women * Histology * monotonous proliferation of uniform, relatively small cells, deeply acidophilic cytoplasm and vesicular nuclei * sheets and cords in a very myxoid stroma * Wide surgical excision is the treatment of choice. * Despite a slow, protracted course, late recurrences and metastases occur commonly.

Answer 13

Langerhans Cell Histiocytosis * Langerhans cell histiocytosis is a neoplastic proliferation of large specialized dendritic cells (Langerhans cells) admixed with a mixed inflammatory population composed of an abundance of eosinophils, neutrophils, lymphocytes, and plasma cells. The disease may be present as a single lesion (monostotic) or as a few or multiple lesions involving several bones and may be associated with involvement of other tissues. * Individuals of any age may be affected, but 80% to 85% of patients are younger than age 30, and 60% are younger than 10 years. There is a male predilection. * Langerhans cell histiocytosis most commonly involves the femur, the bones of the pelvis, and the mandible. In the long bones, it is most often diaphyseal. In adults, the ribs are the most common site. The monostotic form is much more common (80% of cases) than the polyostotic form. * Histology is characterized by the presence of proliferating Langerhans cells intermixed with inflammatory cells, such as lymphocytes, neutrophils, plasma cells, and frequently many eosinophils. The morphologic hallmark of this lesion is a large histiocyte with abundant cytoplasm and a longitudinal nuclear groove imparting a “coffee bean” appearance to the nucleus. Despite the previous name eosinophilic granuloma, eosinophils are not an essential component of the lesion. * The Langerhans cell typically expresses S100 and CD1a. The typical finding on electron microscopy is the cytoplasmic racket-shaped Birbeck granule.

Answer 14

Chondroblastoma * Chondroblastoma is a tumor of immature cartilage, accounting for 1% of bone tumors. It occurs in skeletally immature individuals (first and second decades) and favors the epiphyses of long bones, being typically located in the distal femur, proximal tibia, and proximal humerus. It may involve less frequently the axial bones, vertebrae, and talus and calcaneus. * Clinically, pain—present for several months to several years—is a consistent symptom. There may be associated joint effusion in lesions that reach up to the subarticular endplate. * Radiographically, chondroblastoma is a small lesion (2.5 to 6.0 cm) that causes a sharply demarcated radiolucency circumscribed by a sclerotic rim of bone. Irregular calcifications may be seen. * Chondroblastoma is characterized by cohesive sheets of uniform, small cells with well-defined margins (chondroblasts) that often show a pavementlike architecture. Ill-defined nodules of fluffy acidophilic matrix representing immature cartilage (chondroid) are associated with the cells. Not unusually, chondroblasts may show mitoses (one to two in 10 high-power fields) without atypical figures. Giant cells of various sizes are arranged in clusters distributed throughout the tumor. Calcifications of the chondroid matrix around the chondroblasts form a basophilic mesh (“chicken-wire” calcifications); although these “chicken-wire” calcifications are characteristic of this lesion, they are not always present. The tumor frequently undergoes aneurysmal transformation. The tumor consistently expresses vimentin and S100 and is reported to show positivity for cytokeratins. * In most cases, the tumor has a limited growth potential and follows a benign course. Recurrences occur in about 10% of cases. Benign lung implants (rather than true metastases) can occur and are successfully treated by resection. Aggressive behavior may rarely occur.