IHC

Question 1

GISTs

Answer 1

KIT/CD117(+/-)
SMA(+/-)
Desmin (-)
S-100(-)
Dog-1(+)

Question 2

Hemangiosarcoma

Answer 2

Factor VIII-RAg/vWF(+)
CD31/PECAM-1(+)

Question 3

Lymphangiosarcoma

Answer 3

Factor VIII-RAg(+)
LYVE-1(+)
Prox-1(+)

Question 4

Histiocytic Sarcoma

Answer 4

CD18(+)
CD3(-)
CD79a(-)
Pax5(-)
Iba1(+) – HS from round cell tumors
Hemophagocytic HS = CD11d(+)
CD204(-)

Question 5

Leiomyosarcoma and Leiomyoma

Answer 5

KIT/CD117(-)
SMA (+)
Desmin (+/-) = myogenic origin
S-100 (-)
Dog-1 (-)

Question 6

Mast Cell Tumors

Answer 6

Tryptase (+)
KIT/CD117 (+)
Toluidine blue and Giemsa stain can confirm MCT origin
Vimentin

Question 7

Melanocytic

Answer 7

Melan-A (+/-)
PNL2 (+/-)
Vimentin (+)
S-100 (+)
Tyrosinase (+/-)
TRP-1/TRP-2 (+/-)

Question 8

Rhabdomyosarcoma

Answer 8

Vimentin (+)
Desmin (+)
SMA (-)
Myoglobin (+/-)

Question 9

Neural astrocytic tumors (astrocytoma, glioblastoma, oligodenddroglioma)

Answer 9

GFAP (+)
S-100 (+/-)
Olig2(+/-)

Question 10

Neuroendocrine tumors

Answer 10

Chromogranin A (+/-)
Synaptophysin (+/-)
NSE (+)

Question 11

Plasma Cell Tumor

Answer 11

MUM-1/IRF4 (+)
CD18 (+/-)
CD3 (-)
CD79a (-)
Pax5 (-)

Question 12

Synovial Cell Sarcoma

Answer 12

Vimentin (+)
Cytokeratin (+)
CD18 (-)

Question 13

Thyroid tumor - follicular epithelial origin

Answer 13

Thyroglobulin (+)
TTF-1 (+)
Cancitonin (-)
Chromogranin A (-)
Synaptophysin (-)
NSE (-)

Question 14

Thyroid tumor - C-cell/parafollicular cell origin

Answer 14

Thyroglobulin (-)
TTF-1 (+)
Cancitonin (+)
Chromogranin A (+)
Synaptophysin (+)
NSE (+)

Question 15

Granulosa-theca cell tumor

Answer 15

Inhibin-alpha (+) = specific
Vimentin and S-100 (+)

Question 16

Pheochromocytoma

Answer 16

Chromogranin A (+)

Question 17

TVT

Answer 17

Round cell - suspected of histiocytic origin
Vimentin
Lysozyme
Alpha-1-antitrypsin (AAT)
ACM1 (macrophage-specific)