Soft Tissue Tumors

Question 1

t(2;13)

Answer 1

alveolar rhabdomyosarcoma; fusion of PAX3 and FOXO1 gene

Question 2

t(1;13)

Answer 2

alveolar rhabdomyosarcoma; fusion of PAX7 and FOXO1 gene

Question 3

Subclassifications of rhabdomyosarcomas

Answer 3

embryonal, alveolar, pleomorphic

Question 4

myogenin

Answer 4

confirms rhabdomyoblastic differentiation

Question 5

Amplification of 12q

Answer 5

common in well differentiated liposarcomas, encodes MDM2 which inactivates p53

Question 6

t(12;16)

Answer 6

myxoid liposarcoma

Question 7

Nodular fasciitis

Answer 7

self limited fibroblastic and myofibroblastic proliferation in young adults, upper extremity, grows rapidly over weeks or months, usually <5cm. May have hx trauma. t(17;22)

Question 8

t(17;22)

Answer 8

nodular fasciitis. Produces MYH9-USP6 fusion gene

Question 9

Histologic picture of nodular fasciitis

Answer 9

deep dermis, subcutis, or muscle. Circumscribed or slightly infiltrative, richly cellular, immature fibroblasts, myofibroblasts, gradient of maturation, cells vary in size and shape, conspicuous nucleoli, lymphos and RBCs common. Neutrophils uncommon.

Question 10

Myositis Ossificans

Answer 10

metaplastic repair response. Woven bone in granulation tissue, benign because well formed at periphery but immature at the center. Late stage may contain cartilage or lamellar bone. Follows blunt trauma to muscle.

Question 11

Locally aggressive but don’t metastasize

Answer 11

Fibromatoses

Question 12

herringbone pattern

Answer 12

malignant spindle cells of fibrosarcoma