Primary extragastrointestinal stromal tumors: A clinicopathological and immunohistochemical study-A tertiary care center experience.

Background: Extra gastrointestinal stromal tumors (EGIST) are uncommon compared to their gastrointestinal counterparts. EGISTs involve omentum, mesentery, retroperitoneum, pancreas, and pelvis. Materials and Methods: Ten EGISTs were analyzed in this study from January 1995 to November 2011. They were analyzed with respect to clinical features, imageological, histopathological, and immunohistochemical findings. The immunohistochemical stains used were Smooth muscle actin (SMA), Desmin, S-100 protein, CD34 and CD-117. Results: There was slight female preponderance with wide age range. Four of the tumors were in retroperitoneum, three in mesentery, and two in omentum and one in pelvis. Histopathologically majority were spindle cell tumors. Immunohistochemically CD117 was consistently positive followed by CD34. Smooth muscle actin was positive in eight cases, S-100 protein and desmin were positive in two cases each. Conclusion: EGISTs are rare and should be considered in the differential diagnosis of the mesenchymal tumors and immunohistochemistry helps to confirm the diagnosis. Further study with better follow-up is desired to characterize these uncommon tumors.

Malignant peritoneal mesothelioma deciduoid or anaplastic variant? Point to ponder.

A case of peritoneal mesothelioma displaying unusual morphology, occurring in a 53 year old woman is described. The role of immunohistochemistry and electron microscopy in the evaluation of this tumor is stressed. The appropriate terminology to be used and possible etiologic factor are also discussed.