Itʼs Not Recurrence?

Abstract

Case presentation A 53-year-old man was evaluated for nausea, fatigue and progressive weakness. He had a history of a 20cm (figure A) stage IIIb gastric high-grade, predominantly epithelioid, GIST (figure B, note the epithelioid appearing GIST within the black arrows, the oxyntic mucosa within the blue arrows and the muscularis separating the two areas) extirpated by partial gastrectomy and Billroth II ˜18 months prior. A 3cm LUQ mass was found on surveillance imaging 12 months later while being treated with adjuvant tyrosine-kinase inhibitors. Repeat imaging demonstrated an enlarging 6.7x7.0cm mass within the abdominal mesentery anterior to the left kidney. He was referred for laparoscopic partial small bowel resection and excision of a 10 cm mesenteric mass at the level of the efferent jejunal limb, a 3cm nodule at the level of the proximal ileum and 6 smaller nodules within the small bowel mesentery. Histopathology of the resected masses demonstrated a vimentin positive, uniform, spindled cell lesion with minimal inflammation and a rare mitotic figure. The lack of inflammation, storiform spindled pattern, mucin and obliterative vasculitis, helped exclude inflammatory myofibroblastic tumor and IgG4 disease. CD117 (c-kit) and CD34 were negative, excluding residual or recurrent GIST. However, the spindled cell did demonstrate nuclear and cytoplasmic positivity for beta-catenin, supporting the diagnosis of intra-abdominal mesenteric fibromatosis (figure C). Discussion Mesenteric fibromatosis or desmoid tumor is group of rare benign tumors that can be locally aggressive but do not metastasize. They develop in ˜20% of patients with FAP but can appear spontaneously, with tissue trauma and radiation exposure as reported risk factors. To date, there are about 30 reported cases of mesenteric fibromatosis following GIST resection. Co-existence of mesenteric fibromatosis with GIST has been reported as well. Distinguishing mesenteric fibromatosis from recurrent GIST may be difficult given common similarities in radiologic appearance and c-kit expression. Accurate diagnosis can only be made after surgical removal and histopathologic examination. Unfortunately, surgery for mesenteric fibromatosis is not always curative and high rates of recurrence are common. Watchful waiting should be considered after resection, especially in patients with minimal symptoms.2701_A Figure 1. CT of the abdomen2701_B Figure 2. Epithelioid GIST, 10X2701_C Figure 3. Jejunal mesenteric mass, desmin stain, 20x