Primary gastrointestinal stromal tumor of the liver with PDGFRA gene mutation.

Gastrointestinal stromal tumor is a mesenchymal tumor with KIT or PDGFRA gene mutation, occurring primarily in the stomach and intestine and rarely outside the digestive tract. KIT-negative tumors with epithelioid cell morphology and PDGFRA mutation represent a minor subset of gastrointestinal stromal tumor. Here, we describe a case of gastrointestinal stromal tumor in the liver of a 70-year-old man. The tumor was shown to be completely limited within the liver by radiologic, intraoperative, and pathologic examinations. Histopathologically, the tumor showed epithelioid cell-type morphology and immunohistochemical expression of CD34 and protein kinase C theta but was negative for cytokeratin, EMA, S-100, and HMB-45. KIT protein expression was very faint, and we judged it as negative. Mutation analysis revealed the presence of PDGFRA gene mutation (V561D) at exon 12. These findings are essentially the same as those typically seen in ordinary KIT-negative epithelioid cell-type gastrointestinal stromal tumor of the digestive tract. Although KIT-negative gastrointestinal stromal tumor occurring outside the gastrointestinal tract is very rare, this entity should be considered as a potential primary hepatic neoplasm.