Thin-layer cytopathology of a gastrointestinal stromal tumor (GIST) in effusion: diagnostic dilemmas.

Although gastrointestinal stromal tumors (GISTs) are uncommon, they represent the most frequent mesenchymal neoplasms of the gastrointestinal tract. During recent years, considerable information has been published about the pathogenesis, molecular biology, histological criteria, surgery, and adjuvant pharmacological treatment of GISTs, but there have been few reports about the cytologic diagnosis of GISTs, particularly in effusions; in such specimens these neoplasms cause a wide range of potential pitfalls. In this case report, we show that by combining morphological and immunocytochemical studies on thin layer slide preparations, the cytologic diagnosis of GISTs can be both accurate and efficient.