Cytomorphology of gastrointestinal stromal tumors and extra-gastrointestinal stromal tumors: A comprehensive morphologic study

Abstract

Background:The term gastrointestinal stromal tumors (GIST) is used to refer to those mesenchymal neoplasms of the gastrointestinal tract (GIT) which express CD117, a c-kit proto-oncogene protein.Aims:To study the cytological features of GIST and extra-gastrointestinal stromal tumors (EGIST), to correlate them with histology and to determine cytological indicators of malignancy.Materials and Methods:Cytological smears from patients diagnosed as GIST/EGIST on histology were retrieved. From Jan 2000 to July 2010, 26 GIST (13 primary, 12 metastatic, one recurrent) and seven EGIST (5 primary, one metastatic, one recurrent) cytologic samples from 27 patients were identified.Results:The patients included 20 males and 7 females with a mean age of 50.6 years. Tumor sites included stomach (5), duodenum (5), ileum (2), ileocecal (1), rectum (1), liver (9), retroperitoneum (5), mesentery (1), subcutaneous nodule (1), supra-penile lump (1), ascitic (1) and pleural fluids (1). The smears were cellular with cohesive to loosely cohesive thinly spread irregularly outlined cell clusters held together by thin calibre vessels. The tumor cells were mild to moderately pleomorphic, spindle to epithelioid with variable chromatin pattern and variable cytoplasm. Cellular dyscohesion, nuclear pleomorphism, intranuclear pseudoinclusions, prominent nucleoli, mitosis and necrosis were more prominent in malignant, metastatic and recurrent tumors.Conclusions:GISTs show a wide spectrum of cytological features and the presence of mitosis, necrosis and nuclear pleomorphism can help in prediction of malignant behavior. Further, cytology is a very useful screening modality in patients of GIST and EGIST to detect early recurrence and metastasis at follow-up.

Gastrointestinal Stromal Tumor: A Cytologist’s Perspective

“…This is clinically important as the GIST have potential malignant behavior while the latter two pursue a benign course [3]. Several studies have tried to look at reliable indicators to differentiate GIST from Leiomyoma and although this distinction is difficult, the anatomic site (stomach), moderate to marked cellularity of the clusters, presence of isolated single cells and wispy cytoplasm with nuclear palisading favour GIST over leiomyoma.…”

“…However recently, few authors have established EUS-FNAC as a reliable method for diagnosing GIST and EGIST before surgical procedure [3,6].…”

“…As in the spindled variety, the nuclear chromatin is finely granular, though the nuclear borders are rounded instead of being elongated. Some of the rounded, polygonal cells can be found singly in the background [2,3].…”

“…The name "GIST" was proposed in 1983, but the cell of origin remained unclear until 1998 when interstitial cells of Cajal or their precursors were reported as the cells of origin. Majority of the GIST occur in the stomach (60% to 70%) and small intestine (25% to 35%) with rare occurrence in colon and rectum (5%), esophagus (2%) and appendix [3]. Though primary GISTs are described in the omentum, mesentry or retro-peritoneum, most GISTs in these sites are metastases from stomach or intestine [2,4].…”

“…Instead, they have a unique immunophenotype, expressing c-KIT (CD117), DOG-1 and CD34 in most cases [2]. The introduction of a new targeted treatment for GIST in the form of imatinib mesylate (STI-571, Gleevec), a receptor tyrosine kinase inhibitor, has further validated this entity [3]. An accurate pre-operative cytological diagnosis GIST is therefore important to help the clinician in deciding the treatment plan.…”