A Case of Recurrent Gastrointestinal Stromal Tumor with Chondroid Differentiation

Abstract

Abstract Introduction/Objective Gastrointestinal stromal tumors (GIST) comprise 0.1% to 3% of gastrointestinal neoplasms but are the most common mesenchymal tumors in the gastrointestinal tract. They originate from the interstitial cells of Cajal and most frequently arise in the stomach. However, chondroid differentiation of GIST is extremely rare with less than ten cases reported in the literature. We present a case of a 58-year-old female with recurrent GIST post-imatinib therapy. Methods/Case Report The patient was originally diagnosed with GIST seven years prior when she visited the Emergency Department after a syncopal episode and was incidentally found to have a 11 x 8.5 x 7 cm gastric mass based on abdominal CT scan. She underwent biopsy that showed spindle cell lesion staining positively for DOG1 and CD117 and negatively for desmin, consistent with GIST. She subsequently underwent partial gastrectomy with pathology showing high grade spindle cell type GIST with focal bizarre epithelioid cells and necrosis. Molecular testing identified the tumor to have a c-KIT mutation. Based on large tumor size and risk of recurrence, she was treated with imatinib for three years. Two years after completion of imatinib therapy, her surveillance imaging showed a mass compatible with recurrence measuring 11.8 x 11.7 x 6.7 cm. Additionally, imaging identified a mass in her mid abdomen that was biopsied and showed metastatic GIST supported by immunophenotype. The patient undewent a second partial gastrectomy and the mass on gross examination showed a heterogeneous cut surface displaying some solid and necrotic areas that appears to have invaded adjacent adipose tissue. Histomorphological features showed a spindle component with necrosis and a focus of chondroid differentiation. Tumor cells were immunopositive for DOG1 and CD117. The chondroid component did not stain for either marker. Results (if a Case Study enter NA) NA Conclusion There have been few reported cases of GIST with chondroid differentiation. Moreover, a previous study found three of 35 patients who showed phenotypic alteration post-imatinib therapy with changes ranging from tubulopapillary to epithelioid morphology. However, there has been no case with chondroid differentiation after imatinib therapy reported. This case illustrates the variable response of GIST to imatinib and its possible transformation because of the therapy. To better understand the prognosis of GIST with chondroid differentiation, more cases should be identified, reported, and monitored closely.