Soft tissue selection

Question 1

Clear cell sarcoma /melanoma of soft parts

Answer 1

S100 +
HMB45 +
Melan-A +
EWSR1-ATF1 fusion

Question 2

Dermatofibroma

Answer 2

D2-40 +

CD34 -

Question 3

DFSP

Answer 3

D240 -

CD34 +

Question 4

Epithelioid sarcoma

Answer 4

CK + (strong)
EMA +
CD34 + (50%)
CEA + (focal)
Vimentin +
Loss of INI 1 expression

Note: CK and CD34 co-expression is unique to epithelioid sarcoma and epithelioid angiosarcoma)

Question 5

Ewing sarcoma/PNET

Answer 5

CD99 +
Focal CK in 20%
if SYN/NSE + favours PNET

Question 6

Fibromatosis

Answer 6

Nuclear Beta-catenin (deep only)
Acin +
CD34 - (compare with SFT)
C-kit variable
Abdominal fibrzomatosis ER/PR +

Question 7

GIST

Answer 7

c-KIT + (CD117)
DOG1 +
CD34 + (70%)
BCL2 +
Actin + (30%)

Question 8

Glomus tumour

Answer 8

SMA +
Calponin +
Caldesmon +
Desmin -

Question 9

Granular cell tumour

Answer 9

S100 +
CD68 +
Inhibin +
PAS +

Question 10

Inflammatory myofibroblastic tumour

Answer 10

ALK + (35%)
Actin + (80% - tram tract pattern)
Desmin + (40%)

Question 11

Desmoplastic small round cell tumour

Answer 11

WT1 +
CK +
EMA +
Desmin + (peripheral cytoplasmic accentuation)
Actin - 
NSE +
SYN/Chromogranin - 
CD99 variable

Question 12

Leiomyoma/Leiomyosarcoma

Answer 12

Desmin, actin, caldesmon all +

Question 13

Nodular fasciitis

Answer 13

Myofibroblastic differentiation:
SMA +
Calponin +
Desmin - 
Caldesmon -

Question 14

PEComas

Answer 14

Smooth muscle and melanocytic differentiation:
SMA +
Desmin +/-
HMB45, Melan-A, MITF +
S100 +/-
C-kit +

Question 15

Rhabdomyosarcoma

Answer 15

Desmin +
MSA +
Myogenin + (alveolar >>>> embryonal)
MyoD +
PAX5 in translocated alveolar RMS
p53 in anaplastic type

NB: anapaestic type - muscle markers typically focal

Question 16

Solitary fibrous tumour

Answer 16

CD34+
BCL2 +
Muscle markers -
C-kit - 
EMA -
STAT6 +

Question 17

Synovial sarcoma

Answer 17

Always CD34 - 
BCL2 +
Focal CK and EMA
Calponin +
S100 + in 30%
Always desmin - 
Poorly differentiated SS is usually CD99+

Question 18

Low grade fibromyxoid sarcoma

Answer 18

MUC4 + (sensitive and specific, also + in sclerosis epithelioid fibrosarcoma)