背景和目的：脾臟畸胎瘤合併血小板減少症是非常少見的病例。方法：依據手術前臆斷無功能性左腎上腺腫瘤進行剖腹探查術。結果：本文報告脾臟畸胎瘤因其生長的大小及位置極似左側腎上腺腫瘤，故在術前診斷上較困難。手術中發現是一巨大多狀葉狀脾臟，病理組織證實是脾臟畸胎瘤合併囊腫退化及囊腫壁鈣化。結論：本文報導一罕見脾臟畸胎瘤合併血小板減少症，而在術前因腫瘤生長位置及方式易被誤認為左腎上腺腫瘤。手術摘除脾臟後血小板即恢復正常。

Background and Purpose: A 45-year-old man was referred to our hospital because of aleft adrenal gland tumor. CT scan of the abdomen showed a 13 × 12 × 10-cm nodular soft-tissuemass with heterogenous enhancement and some central necrosis in the left upper retroperitoneum.A nonfunctioning left adrenal gland tumor was diagnosed. Methods: Exploratory laparotomywas performed under the impression of a nonfunctioning left adrenal gland tumor. Results:During the operation, a large multilobulated spleen was noted. A few days after the surgicalremoval of the spleen, the platelet count returned to a normal range. The histologic diagnosis of thesplenic tumorwas a hamartoma associated with secondary cystic degeneration and calcification ofthe cyst wall. Microscopically, the splenic tumor, which consisted of red pulp tissue, wasdiagnosed as a splenic hamartoma. Conclusion: This paper reports a rare case of a splenichamartoma associated with thrombocytopenia which can easily be misdiagnosed because itmimics a left adrenal gland tumor.Removal of the enlarged spleen resulted in sustained clinical andhematologic improvement.