Extragastrointestinal stromal tumor in a kidney transplant recipient.

The occurrence of de novo malignant neoplasms has been shown in post-transplant recipients receiving immunosuppressive treatment. We present a case of a rare extragastrointestinal stromal tumor (EGIST) located in the pelvic cavity of a kidney transplant patient. A 57-year-old female patient was admitted to our department because of non-specific lower abdominal pain 6 months after renal transplantation. An abdominal computed tomography scan showed a 4.5 cm diameter pelvic tumor mass. The tumor was resected en bloc and confirmed as not being connected to the gastrointestinal wall. Microscopically, the tumor consisted of typical spindle cells with 2-3 mitotic figures per 50 high-power fields. Immunohistochemically, the tumor cells were strongly positive for CD117 (c-kit), and negative for CD34, SMA, s-100 protein, and desmin. Genetically, the tumor showed a silent mutation in exon 18 of the PDGFRA gene at codon 824 GTC > GTT (V824V) [rs2228230]. No recurrence was noted 24 months after the operation. This case draws our attention to the importance of considering EGISTs (including GISTs), even though they are extremely uncommon, in the differential diagnosis of mesenchymal neoplasms, especially in transplant patients.