RESUMO
BACKGROUND: Digestive stromal neoplasms are the most frequent undifferentiated mesenchymal tumors. The outcome of these malignancies is difficult to predict and the histogenesis is still controversial. However, the frequent and specific expression of CD117 (c-kit) by these tumors could imply an origin from interstitial cells of Cajal. Our objective was to analyze the role of fine needle aspiration cytology, cell block preparation, and immunocytochemistry in the interpretation of gastrointestinal stromal tumors, and to establish scanning electron microscopy as a useful research aid for pathologic changes of the surface cells of gastrointestinal stromal tumors, not totally appreciated by light microscopy. MATERIAL AND METHODS: Twelve cases of gastrointestinal stromal tumors were included in this study, in which fine needle aspiration cytology was performed. RESULTS: On aspirated material, the tumor cells formed closely packed cohesive tissue fragments with high cellular density often in bloody background, or fascicles with parallel side-by-side arrangements of the nuclei. On cell block biopsy material, gastrointestinal stromal tumors were highly cellular spindle or epithelioid tumors with basophilic appearance. Immunocytochemically, they were CD117 positive in all twelve cases, CD34 positive in nine, weakly smooth muscle actin-positive in five, and S-100 and GFAP-negative in all cases. The scanning electron microscopy study showed a strong correlation with the cytomorphological profile. CONCLUSIONS: Gastrointestinal stromal tumors show a broad morphologic variety, but nuclear pleomorphism by cytology alone, rarely correlates with malignant potential. In the appropriate clinical and radiological setting, a confident diagnosis of gastrointestinal stromal tumors can be documented by fine needle aspiration cytology, cell block, immunocytochemical, and scanning electron microscopy results.
