GIST with a Twist—Upregulation of PDGF-B Resulting in Metachronous Gastrointestinal Stromal Tumor and Dermatofibrosarcoma Protuberans

Case Report A 61-year-old male was referred following an incidental radiological discovery of an intra-abdominal mass. His medical history included excision of a lumbar dermatofibrosarcoma protuberans (DFSP) 5 years previously. A CT scan of the abdomen revealed a mass arising from the greater curvature of the stomach. Upper GI endoscopy was normal. He underwent successful laparoscopic resection of this mass. Materials and Methods The histology of the abdominal mass revealed a gastrointestinal stromal tumor (GIST) with poor prognostic indicators. Immunohistochemical analysis of the GIST and his previous DFSP was performed. Results Immunohistochemistry suggested a link between the GIST and his previous DFSP involving the PDGF signalling system. Discussion Both GIST and DFSP are extremely rare tumors. A mutation in the platelet-derived growth factor receptor alpha (PDGFR-α) has been described in 5–15% of GISTs. It has been shown that DFSP is frequently associated with a translocation between PDGF-B (Chr 22) and COL1A1 (Chr 17), causing continuous activation of PDGFR-β. Literature review confirms that there are no previously reported cases of both of these tumors occurring in the same patient. Conclusion We hypothesize that this patient may have a previously undescribed genetic mutation involving the PDGF signalling system, resulting in these two very rare malignancies. Immunohistochemistry studies confirmed the link on this occasion. Improvements in our understanding of the molecular biology of the PDGF system may novel therapeutic targets in the future.