Gastrointestinal stromal tumours can express CD10 and epithelial membrane antigen but not oestrogen receptor or HMB45.

AIMS: Gastrointestinal stromal tumour (GIST) may share morphological and/or immunohistochemical features with various intra-abdominal neoplasms, including endometrial stromal sarcoma, perivascular epithelioid cell tumour (PEComa), melanoma and synovial sarcoma. Each of these various neoplasms has characteristic immunohistochemical markers, including epithelial membrane antigen (EMA), CD10, oestrogen receptor alpha (ERa) and/or HMB45, and therefore the primary aim of this study was to determine whether these markers are also expressed by GISTs.

METHODS AND RESULTS: Standard size sections of 52 GISTs were immunostained for EMA, CD10, ERa and a melanoma marker cocktail (targeting HMB45 and melan-A). Ten GISTs (19%) showed CD10 immunopositivity. This positivity was confined almost completely to small intestinal GISTs, and was seen among spindle cell GISTs but not epithelioid or mixed cell-type GISTs. Five of the 52 GISTs (9.6%) showed EMA immunopositivity. This positivity was always focal and usually seen in a perivascular location. None of the GISTs showed immunopositivity for ERa or the melanoma marker cocktail.

CONCLUSIONS: GISTs occasionally show CD10 immunopositivity (especially small intestinal spindle cell GISTs), and infrequently show focal EMA positivity. GISTs do not show immunopositivity for ERa or HMB45.