Simultaneous gastrointestinal stromal tumor (GIST) and desmoid fibromatosis (DF)

Abstract

10568 Background: Desmoid Fibromatosis (DF) is one of a group of rare fibrous tissue proliferations (2–4 cases per year per million) which tend to be locally aggressive but have no propensity for metastasis. Gastrointestinal Stromal Tumor (GIST) is the most common mesenchymal tumors of the gastrointestinal tract and also rare (15–20 cases per year per million). Anecdotal reports of individuals with both diseases led us to investigate the number of patients at our institute with both types of cancer and their clinical, and histopathologic features. Methods: We identified four cases of GIST associated with DF at the M. D. Anderson Cancer Center between 1995 and 2008 using an IRB-approved protocol. Two more cases were identified from the patient database at the University of Helsinki. Results: Our patients were three men and three women aged from 39 to 66. Two patients were African Americans and 3 were Caucasians. In 5 cases, the GIST was diagnosed prior to the DF while one case had both tumors synchronous at presentation. The primary site of the GIST was gastric in 4 cases and the others were jejunal and mesenteric. Three patients had their DF occur in the surgical incision site mimicking a recurrence of GIST. The 3 others were intra-abdominal DF. There were no cases of DF occurring outside of the GI tract. One GIST patient was metastatic at presentation and one developed metastasis before DF was diagnosed. In 5 cases, imatinib mesylate was administered to the patients with partial response. In all cases KIT expression was observed immunohistochemically for GIST and but not for DF. Additionally, all cases of DF but no cases of GIST were found to have beta-catenin expression by immunohistochemistry. Conclusions: Our findings suggest that concurrent DF may occur in patients with GIST. Additionally, DF may mimic the recurrence of GIST or imatinib resistance. The association of these two sarcomas should be further explored. No significant financial relationships to disclose.