Sir, Abdominal stromal tumors are relatively uncommon. Based on the expression of marker proteins and ultra- structural characteristics, stromal tumors are currently separated into three major categories consisting of myo- genic tumors (i.e., leiomyomas or leiomyosarcomas), neurogenic tumors, and gastrointestinal stromal tumors (GIST) [16, 17, 20]. Most previously diagnosed myogen- ic tumors are re-diagnosed as GIST according to their histological characteristics and immunohistochemical features. Primary pancreatic stromal tumors are extreme- ly rare, and there is no report that has completely exam- ined the histological characteristics and immunohisto- chemical features. We report a case of histologically and immunohistochemically diagnosed leiomyosarcoma of the pancreas. A 52-year-old woman was admitted to a community hospital with general malaise and obstructive jaundice due to a tumor in the pancreatic head. After percutaneous transhepatic biliary drainage, she was transferred to our hospital for surgery. Abdominal computed tomography (CT) showed a 2-cm low-density tumor in the pancreatic head. Abdominal angiography revealed a hypervascular mass in the pancreatic head without major vascular en- casement. On laparotomy, a mobile 2-cm tumor invading the duodenum was palpable in the pancreatic head with- out evidence of peritoneal dissemination or hepatic me- tastasis. Pylorus-preserving pancreaticoduodenectomy with regional lymph node dissection was performed. Af- ter surgery, her postoperative course was uneventful, and there has been no sign of recurrence to date (1 year post- operatively). Macroscopically, the yellowish 1.5×1.5-cm firm tu- mor was seen to be located in the pancreatic head with invasion into the duodenal mucosa (Fig. 1a). Microscop- ically, the tumor consisted of uniform-sized spindle cells with slight eosinophilic cytoplasm and showed moderate cellularity and nuclear atypia (Fig. 1b). Tumor cells formed interlacing bundles and mitoses were observed. Neither histological necrosis nor hemorrhage was seen, and there was no vessel invasion by tumor cells. Im- munohistochemically, tumor cells were positive for des- min, α-smooth muscle actin (α-SMA), and vimentin, while S-100, KIT, and CD34 were negative (Fig. 1c, d, e, f, g, h). Thus, the tumor was diagnosed as pancreatic leiomyosarcoma with low-grade malignancy. During the past two decades, histological and molecu- lar characterization of stromal tumors in the gastrointes- tinal tract has greatly advanced [16, 20]. Most previously diagnosed leiomyomas and leiomyosarcomas have been re-classified as GIST, and gain-of-function mutation of the c-kit gene is considered causative for GIST [10, 21]. Only 10% of stromal tumors in the gastrointestinal tract are myogenic (leiomyomas and leiomyosarcomas). Simi- lar stromal tumors, extra-gastrointestinal GISTs, are also reported in the gallbladder, retroperitoneum, and urinary tract [16, 20]. Their diagnosis is mainly based on immu- nohistochemical characteristics including expression of specific marker proteins. Stromal tumors are usually di- agnosed as myogenic when they are diffusely positive for desmin, as neurogenic when positive for the S-100 protein, or as GIST when positive for KIT [10, 16, 20]. Vimentin and α-SMA are not considered specific be- cause these marker proteins may be expressed in GIST, myogenic tumors, or neurogenic tumors. In our case, the stromal tumor was positive for desmin, α-SMA, and vi- mentin, and negative for S-100, KIT, and CD34, indicat- ing immunohistochemical features compatible with leio- myosarcoma. Primary pancreatic stromal tumors are rare, their inci- dence estimated to be less than 0.1% of all pancreatic tu- H. Komoda · T. Nishida ( ✉ ) · T. Yumiba · K. Nishikawa T. Kitagawa · T. Ito · H. Matsuda Department of Surgery, Osaka University Graduate School of Medicine, Yamada-oka 2-2, Suita 565-0871, Osaka, Japan e-mail: toshin@surg1.med.osaka-u.ac.jp Tel.: +81-6-68793151, Fax: +81-6-68793159 S. Hirota Department of Pathology, Osaka University Graduate School of Medicine, Osaka, Japan Virchows Arch (2002) 440:334–337 DOI 10.1007/s00428-001-0557-x LETTER TO THE EDITOR Hiroshi Komoda · Toshirou Nishida Takeyoshi Yumiba · Kazuhiro Nishikawa Toru Kitagawa · Sei-ichi Hirota · Toshinori Ito Hikaru Matsuda Primary leiomyosarcoma of the pancreas – a case report and case review Received: 6 August 2001 / Accepted: 24 September 2001 / Published online: 15 December 2001 © Springer-Verlag 2001