Soft Tissue

Question 1

Angiosarcoma

Answer 1

can show prominent intravascular lymphocytes (in our case they were predominantly T cells)

Question 2

Perineurioma

Answer 2

• looks almost like a neurofibroma or DF but when you look closer it has a perineural whorling
• “Pacinian corpuscle” appearance
• claudin-1, EMA positive

Question 3

Soft Tissue Pearl #1

Answer 3

• If you see atypia, but not the number of mits you would expect for the atypia, consider something B9
• Atypia + mits you can feel more confident it is malignant

Question 4

Epithelioid angiosarcoma

Answer 4

• can arise in schwannoma (consider if long hx of mass)
• has slate grey cytoplasm (unique)
• can be keratin +
• consider angiosarc if your DDx includes papillary endothelial hyperplasia outside of a vessel (PEH should be intravascular)
• known to arise in foreign body sites (?perhaps granulation tissue gone bad?)

Question 5

Desmoplastic melanoma

Answer 5

Lymphoid aggregates
neurotropic
often mistaken for either NF or MPNST (S100+)
hematogenous spread, unlike other melanomas
S100/SOX10+, HMB45-

Question 6

PHAT

Answer 6

looks like schwannoma, but S100 negative

Question 7

Post-operative spindle cell tumor

Answer 7

organized into fascicles that can look like leiomyosarcoma (used to be called this in the past)

Question 8

Angiofibroma

Answer 8

staghorn HPC-like and myxoid liposarc-like vessels

benign

Question 9

Aneurysmal fibrous histiocytoma

Answer 9

?

Question 10

Synovial Sarcoma

Answer 10

• Monotonous, loong fascicles (as does MPNST and fibromatosis)
• can be keratin, EMA negative (but do both stains b/c usually positive)
• a “positive” keratin is strong but focal; reconsider dx if strong and diffuse
• can arise from/around nerve, doesnt make it an MPNST- do the FISH
• can be S100 positive?
• can have collagen, myxoid, or boney areas
• mast cells, gunmetal blue?

Question 11

Perpendicular fascicles

Answer 11

Smooth muscle things (help to contract)

Question 12

Loong fascicles

Answer 12

• synovial sarcoma
• MPNST
• fibromatosis

Question 13

Granular cell tumor cell of origin

Answer 13

Schwann cell - s100 positive (neural crest)

Question 14

Pleomorphic adenoma genetics

Answer 14

PLAG

Question 15

MDM2 mutated

Answer 15

• well diff liposarc/ALT
• parosteal osteosarc
• intimal sarcoma

Question 16

XRT atypia

Answer 16

Use background endothelial or schwann cells as an internal control. For carcinoma, expect some level of cohesiveness

Question 17

Giant cell tumor vs chondroblastoma

Answer 17

Can be a diagnostic pitfall:
Giant cell tumor p63 positive
Chondroblastoma s100/dog1 pos
Chondroblastoma have giant cells full of hemosiderin and chicken wire calcs