Epithelioid Gastrointestinal Stromal Tumors: A Retrospective Look

Abstract Objectives Gastrointestinal stromal tumor (GIST) is the most common primary mesenchymal tumor of the gastrointestinal tract (GIT). Most tumors are of spindle cell type. Approximately 20% of the cases are of epithelioid histologic variant and approximately 10% are mixed epithelioid and spindle type. We sought to identify the clinical and pathologic features of GIST with epithelioid features diagnosed at our institute. Methods The database was searched (2017-2018) and 26 cases were included for the series. The data were analyzed systematically for histologic subtype, age, site, stage, risk group, and immunohistochemical findings. Results Pure epithelioid GIST (PE-GIST) was seen in nine cases (35%). Seventeen tumors were mixed subtype (M-GIST). PE-GIST was more common in females. Mean age of patients was similar in both subtypes. PE-GIST most commonly involved stomach (n = 8). Small intestine was the most commonly involved by M-GIST (n = 10). Mixed tumors were larger in size (6.0 cm, mean) compared to PE-GIST (4.2 cm, mean). Tumors showing pure epithelioid subtype were more in the high-risk category, compared to the mixed subtype (33% vs 23%). Most cases of M-GIST were pT3. M-GIST expressed both c-Kit and DOG-1 more frequently than the PE-GIST (70% vs 55%). Conclusion Mixed epithelioid and spindled GIST was more common than the pure form. Coexpression of DOG-1 and c-Kit was less frequent in PE-GIST. Mixed tumors tend to have higher stage than the pure type at presentation.