Table 3.

Proposed diagnostic criteria for GALT-associated carcinoma compared with 2 main mimics: conventional adenocarcinoma invading GALT and inverted colorectal adenoma (misplaced adenomatous glands)

Essential morphological criteria
Gross findings  Submucosal nodule or raised plaque (1 reported case of a pedunculated lesion)
Microscopic findings  Nodule with sharp borders and pushing margins (pushing growth pattern)  Dense lymphoid stroma with germinal centers  Well-formed glands with minimal architectural disruption  Cystic glands filled with amorphous eosinophilic material  Absence of goblet cells (MUC2-negative)  No desmoplasia (presence suggests associated conventional adenocarcinoma)  No tumour budding or small isolated clusters of cells  No lymphovascular invasion  High-grade dysplasia on the mucosal surface
Differential diagnoses
Misplaced adenomatous glands  Invagination of adenomatous glands from surface epithelium into GALT  Lamina propria surrounding/cuffing the displaced glands  Tubular architecture and/or villous projections
Conventional adenocarcinoma invading GALT  Infiltration of GALT by a conventional adenocarcinoma  Presence of desmoplasia  Infiltrative, irregular margins  Small fused glands containing dirty necrosis  Tumour budding or small isolated clusters of cells may be present  Lymphovascular invasion may be present  Extension beyond lymphoid tissue may occur

Adapted from Fallas et al¹¹.

GALT, gut-associated lymphoid tissue.