Fine needle aspiration cytology of primary and metastatic gastrointestinal stromal tumour.

Abstract

To explore the cytological spectrum of the gastrointestinal stromal tumour (GIST) including its metastatic sites. A total of 42 patients (45 sites) diagnosed with GIST or its metastases on fine needle aspiration cytology were studied over a period of 5years. May-Grünwald Giemsa- and haematoxylin and eosin-stained smears were reviewed and analysed for the cytomorphological spectrum ofGIST. Primary GIST alone was seen in 24 cases, E-GIST in eight cases and metastasis in 11 cases (one patient showing metastasis at two distinct sites), whereas concurrent primary and metastatic lesions were noted in two cases. Amongst primary sites, the most commonly affected location was stomach (n = 22), followed by ileum (n = 2), duodenum (n = 1) and rectum (n = 1). Extra-GIST was seen in retroperitoneum and pelvis (n = 3 each), omentum and mediastinum (n = 1 each). Fine needle aspiration cytology was done from 11 metastatic sites of GIST which included liver, gall bladder fossa, chest wall, and thigh. The classic spindle cell arrangement was the predominant cytological pattern. About 8.8% cases showed predominant epithelioid cell morphology and 15.5% cases had a mixed cytomorphology comprising of both spindle cell and epithelioid cell patterns. Nuclear pseudoinclusions, perinuclear vacuoles and multinucleation were seen in four cases. Immunocytochemistry on cell-block sections for confirmation was performed in 18 cases and all these cases showed strong c-KIT positivity. In this largest case series of cytomorphological diagnosis of GIST, we describe the cytomorphology and immunocytochemistry of primary and metastatic GIST. GISTs with predominant epithelioid cell morphology may pose a diagnostic dilemma therefore in all suspected cases of GIST, immunocytochemistry for c-KIT and/or DOG1 should be employed on cell-block preparations to confirm the diagnosis of GIST.