Primary extragastrointestinal stromal tumors in the omentum and mesentery: a clinicopathological and immunohistochemical study

Abstract

Background/aims: This study aimed to describe the clinical, histological and immunohistochemical characteristics of primary extragastrointestinal stromal tumors (EGISTs) of the omentum and mesentery diagnosed in the Hospital 12 de Octubre, in Madrid, Spain, from 1993-2005.

Methodology: The clinical data and histological and immunohistochemical findings of primary mesenchymal neoplasias were revised using the Department of Pathological Anatomy databases.

Results: Six EGISTs were identified. Three were primarily of the omentum and 3 mesenteric. They were found in 4 males and 2 females with an average age of 65.16 years. All were c-KIT positive, and the majority CD34 positive, while 3 were positive for muscle-specific actin. The 3 omentum cases had a mixed spindle/epithelioid pattern and low mitotic rate, while the 3 mesenteric cases had a spindle pattern, with a high mitotic rate in 2 cases, where hepatic metastasis appeared at 6 and 32 months respectively. The 3 omentum cases were alive at the time of writing, and free of disease at 16, 21 and 34 months of follow-up. EGISTs represent 11.9% of GIST cases diagnosed in the hospital over the period 2000-2005.

Conclusions: In this study primary EGISTs of the omentum and mesentery showed clinicopathological and immunohistochemical characteristics similar to those previously in the literature for GISTs of the digestive tract, which supports the hypothesis that these tumors originate from extragastrointestinal c-KIT positive cells. Mesenteric location appears to be associated with a poorer prognosis.