Soft tissue

Question 1

nonneoplastic mimics of malignancy

Answer 1

fat necrosis

nodular fasciitis

proliferative fasciitis/myositis

ischaemic fasciitis

myositis ossificans

intravascular papillary endothelial hyperplasia

idiopathic retroperitoneal fibrosis (vs sclerosing WDL)

Question 2

pleomorphic lipoma vs ALT/WDL

Answer 2

PL:

superficial

back and neck of older men

well circumscribed

floret cells

inconspicuous vessels

CDK4, MDM2-

Question 3

cellular angiolipoma vs Kaposi sarcoma

Answer 3

CAL:

subcutaneous

well circumscribed

small vessel thrombi

mature fat

Question 4

lipoblastoma (features)

Answer 4

<10yo

lipoblasts in myxoid stroma

PLAG1 rearrangement (cf DDIT3 in myxoid liposarcoma)

Question 5

neoplastic benign mimics of malignancy

Answer 5

lipoma variants

rhabdomyoma

ancient schwannoma

bizarre neurofibroma

atypical leoimyoma

PHAT

IMT

angiomatoid fibrous histiocytoma

Question 6

malignant mimics of benign

Answer 6

well differentiated liposarcoma

low grade fibromyxoid sarcoma

epithelioid sarcoma

angiosarcoma in breast

Kaposi sarcoma

Question 7

nearly normal malignancy

Answer 7

WDL/ALT

Kaposi sarcoma

Question 8

scalp lesions - think of…

Answer 8

meningioma

angiosarcoma

Question 9

shoulder/neck - think of…

Answer 9

spindle cell lipoma

nuchal-type fibroma (assoc with Gardner syndrome)

elastofibroma

Question 10

abdominal wall - think of…

Answer 10

endometriosis

endometrial stromal sarcoma

vulval/vaginal soft tissue tumours

adenocarcinoma (Sister Mary Joseph nodule)

mesothelioma

Question 11

HPC vessels

Answer 11

solitary fibrous tumour (incl HPC dura/sinonasal)

synovial sarcoma

mesenchymal chondrosarcoma

nasopharyngeal angiofibroma

meningioma

MPNST

thymoma

infantile fibrosarcoma

myofibromatosis

endometrial stromal sarcoma

Question 12

myxoid tumours - adipocytic

Answer 12

benign: spindle cell lipoma
malignant: myxoid liposarcoma (lipoblasts, crow’s feet vessels, DDIT3 rearr.)

Question 13

myxoid tumours - fibroblastic

Answer 13

benign: myofibroma (usu <2yo, myofibroblasts, HPC vessels, fibromyxoid stroma)

malignant:

low grade fibromyxoid sarcoma (young, pelvis, whorled spindle cells +/- giant rosettes, FUS rearr.)

myxofibrosarcoma (older, subcut, curvilinear vessels, pleomorphic)

myxoinflammatory fibroblastic sarcoma (hands and feet, R-S like cells)

Question 14

myxoid tumours - unknown differentiation

Answer 14

benign: myxomas

intermediate:

ossifying fibromyxoid tumour (older males, limbs, subcut, cords of round cells, shell of lamellar bone, phf1 gene rearr.)

mixed tumour (CK+ cf myxoid chrondrosarc, s100+ cf metastatic ca)

malignant: extraskeletal myxoid chrondrosarcoma (lobular, cellular at periphery, EWS rearr.)

Question 15

myxomas

Answer 15

intramuscular myxoma (esp thigh/pelvis, cellular but no vessels cf MLS/MFS)

juxtaarticular myxoma (esp knee)

digital fibromyxoma

superficial angiomyxoma (head/neck/trunk/genital, thin walled vessel, epithelial component eg cyst, assoc. Carney complex)

deep aggressive angiomyxoma (vulva/pelvis, infiltrative, thick vessels, myoid bundles around vessels)

Question 16

nerve sheath myxoma vs neurothekeoma

Answer 16

NSM (prev. ‘myxoid’ or ‘classical’ neurothekeoma): rare, extemities esp fingers/knee, myxoid nodules with fibrous border, s100 stong+

Neurothekeoma (prev. ‘cellular neurothekeoma’): young adults, upper body, solid or whorled nests in hyaline collagen, +/- myxoid areas, s100-

Question 17

sclerotic tumours

Answer 17

sclerosing epithelioid fibrosarcoma

epithelioid haemangioendothelioma

Question 18

storiform pattern

Answer 18

DF

DFSP

nodular fasciitis

UPS

Question 19

herringbone pattern

Answer 19

synovial sarcoma

MPNST

fibrosarcoma (eg transformation of DFSP)

leiomyosarcoma

melanoma

spindle cell rhabdomyosarcoma

Question 20

rhabdoid tumours

Answer 20

proliferative fasciitis/myositis

LMS

RMS

epithelioid sarcoma, proximal type

MPNST (Triton tumour)

melanoma

Question 21

epithelioid tumours

Answer 21

‘CAMELS CAMP’

carcinoma

angiosarcoma

melanoma

epithelioid sarcoma

leiomyosarcoma

synovial sarcoma

clear cell sarcoma of soft parts

alveolar soft part sarcoma

MPNST

PEComa

Question 22

small round blue cell tumours - adult

Answer 22

lymphoma

small cell carcinoma

desmoplastic small round cell tumour (CK, WT1, desmin+, EWS-WT1 fusion)

Merkel cell carcinoma

mesenchymal chondrosarcoma (10-40, axial skeleton, chondroid diff, HPC vessels)

small cell osteosarcoma (esp knee)

round cell liposarcoma

synovial sarcoma

Question 23

small round blue cell tumours - children

Answer 23

lymphoblastic lymphoma

alveolar RMS, solid subtype (CK, WT1, desmin+, PAX3 and PAX7 rearr.)

Wilms tumour (CK, WT1, desmin+, WT1 del or mutation)

medulloblastoma

Ewing sarcoma (membranous cd99, EWS rearr.)

neuroblastoma

retinoblastoma

small cell osteosarcoma

hepatoblastoma

Question 24

biphasic tumour

Answer 24

usually:

synovial sarcoma

carcinosarcoma

mesothelioma

Wilms tumour

sometimes:

MPNST, germ cell tumour, mixed GIST, thymoma, myoepithelioma

Question 25

vacuolated cytoplasm

Answer 25

liposarcoma

vascular tumours

smooth muscle

RMS

myxofibrosarcoma

chordoma

Question 26

nested/alveolar tumours

Answer 26

nested: phaeochromocytoma, paraganglioma, RCC, TCC, granular cell tumour, melanoma, PEComa
alveolar: alveolar soft part sarcoma, alveolar RMS, alveolar lobular breast ca

Question 27

high grade spindled tumours

Answer 27

dediff liposarcoma

pleomorphic liposarcoma

leiomyosarcoma

pleomorphic RMS

MPNST

angiosarcoma

myxofibrosarcoma

UPS

carcinoma, melanoma, mesothelioma

Question 28

LG fibromyxoid sarcoma vs myxofibrosarcoma

Answer 28

MFS:

more atypia

infiltrative

purely myxoid

no rosettes

LGFMS:

may have rosettes

t(7;16) (FUS)

Question 29

malignancy in soft tissue leiomyoma

Answer 29

limbs: >1 mitosis/50HPF

retroperitoneum in women: >10/50HPF

(cf uterus: complex tables based on cell type, atypia, necrosis and mitoses)