Abstract

The gastrointestinal mesenchymal tumors (GIMTs) form a heterogenous group with controversy centering on both the cell of origin and the prediction of clinical behavior. They include a small group of tumors with mature smooth muscle or Schwann cell differentiation and a larger group with inconsistent or no evidence of differentiation. Tumors in the latter are now referred to as gastrointestinal stromal tumors (GISTs). A clinicopathologic and immunohistochemical study was performed on 53 cases of GIMTs to identify cellular differentiation and predictors of clinical behavior. Fifty three cases of GIMTs could be histologically and immunophenotypically divided into three categories, 6 leiomyomas (11.3%), 4 schwannomas (7.6%), and 43 GISTs (81.1%). All leiomyomas (SMA desmin ) and schwannomas (S-100 ) were located in stomach and negative for CD34 and CD117. Thirty nine cases of GISTs were either CD34 (n=26) or CD117 (n=23) immunoreactive. Of these 39 GISTs, 26 were negative for myoid (SMA, desmin) and neural marker (S-100), 10 SMA desmin-S-100-, two SMA-desmin-S-100 , and one SMA desmin-S-100 . Two out of 4 GISTs, which were negative for CD34 and CD117, were immunohistochemically considered leiomyosarcoma (SMA desmin ). GISTs of small intestine had a tendency to be malignant than those of stomach. Pathologic grade of GISTs was not correlated with cellular differentiation. In 29 GISTs with clinical follow-up information, tumor size, mitotic counts, Ki-67 labelling index, tumor necrosis, mucosal invasion, and CD34 expression were significantly correlated with metastasis/recurrence.

• Keywords: Gastrointestinal mesenchymal tumor;Gastrointestinal stromal tumor;Leiomyoma;Schwannoma;