Lower GI

Question 1

Spindle cell lesions small bowel

Answer 1

GIST

schwannoma

gangliocytic paraganglioma

inflammatory fibroid polyp (ileum)

Question 2

Spindle cell lesions large bowel

Answer 2

ganglioneuroma (ganglion cells)

perineurioma (EMA+)

mucosal schwann cell hamartoma (s100+)

leiomyoma (desmin+)

lipoma

Question 3

Spindle cell lesions mesentery

Answer 3

mesenteric fibromatosis

inflammatory myofibroblastic tumour

sclerosing mesenteritis

Question 4

Benign mimics of malignancy (7)

Answer 4

pseudoinvasion/colitis cystica profunda

endometriosis

extramedullary haematopoiesis (omentum)

ruptured appendiceal mucous retention cyst

malakoplakia

bizarre stromal cells (inflammatory polyps)

glomus coccygeum

Question 5

Malignant mimics of benign

Answer 5

small mets in fat

pseudomyxoma peritonei with scanty epithelium

Question 6

almost normal

Answer 6

amyloid

emboli

vasculitis

small mets in fat

Question 7

DDX inflammatory bowel disease

Answer 7

infection

drugs

microscopic colitis

ischaemic colitis

diverticulitis

radiation colitis

Question 8

granulomas large bowel

Answer 8

Crohns

infection:

TB

yersinia

chlamydia (usually periappendicitis 2^o to PID)

syphilis

foreign body

sarcoid

Question 9

serrated polyps

Answer 9

hyperplastic

SSA

SSA with cytological dysplasia

traditional serrated adenoma

Question 10

carcinoma vs pseudoinvasion

Answer 10

carcinoma: irregular confluent crypts, dysplasia, atypical mitoses, desmoplasia
pseudoinvasion: lamina propria, haemorrhage/haemosiderin

Question 11

prolapse-induced inflammatory polyp (mucosal prolapse syndrome) - morphology

Answer 11

fibromuscular hyperplasia of LP

thickened and splayed muscularis mucosae

crypt distortion

variable inflammation

Question 12

hamartomatous polyps

Answer 12

Peutz-Jegher polyp

juvenile polyp

Cronkite-Canada (histo same as juvenile polyp)

Question 13

Crohns vs UC

Answer 13

Crohns: skip lesions, transmural lymphoid aggregates, granulomas unrelated to ruptured crypts, fissures

Question 14

Whipples vs MAIC

Answer 14

MAIC: ZN+, culture/PCR

(nb: both are PAS+)

Question 15

Crohns vs yersinia vs TB

Answer 15

TB: necrotising granuloma (ZN+)

• Y. pseudotuberculosis*: suppurative granulomas (gram/WS+)
• Y. enterocolitica*: microgranulomas (gram/WS+)

Also: lymphoid cuff in infection, uncommon in Crohns. Macro correlation (cobblestoning and creeping fat)

Question 16

juvenile vs inflammatory polyp

Answer 16

Clinical

juvenile polyp: young, polyposis syndrome, absent underlying inflammatory disorder

Question 17

goblet cell carcinoid vs MANEC

Answer 17

MANEC (signet ring type): atypia, single cells, desmoplasia, irregular large clusters

MANEC (poorly diff adenoca type): same, plus >1LPF conventional adenoca and p53+

Question 18

carcinoid vs goblet cell carcinoid

Answer 18

carcinoid: diffuse NE markers, no intracytoplasmic mucin (NB: mucin in lumen in tubular NET), CK7-, CK20+/-

GCC: scattered NE markers, intracytoplasmic mucin, CK7+/-, CK20 always+

Question 19

epithelioid lesions small and large bowel

Answer 19

carcinoma (primary or met)

neuroendocrine tumours

melanoma

lymphoma/plasmacytoma

adenomatoid tumour

mesothelioma

germ cell tumour

mesenchymal:

epithelioid GIST/LMS/MPNST)

glomus tumour

PEComa

angiosarcoma

Question 20

mucinous lesions of appendix

Answer 20

adenoma: usu villous, m/mucosae intact

LAMN: epithelium on fibrotic stroma (no LP)

adenocarcinoma

PMP (assoc with LAMN and adenoca)