p40陰性肺類基底細胞型扁平上皮癌の1例

p40 Negative Basaloid Squamous Cell Carcinoma of the Lung；Report of a Case

はじめに　肺類基底細胞型扁平上皮癌（basaloid squamous cell carcinoma：BSC）は1992年にBrambillaらによって報告され1），本邦では肺癌取扱い規約第6版より扁平上皮癌の特殊型として収載されている．まれな組織型であり，診断には免疫染色が有用である2）．われわれはp40陰性であるが肺類基底細胞型扁平上皮癌と診断した症例を経験したので報告する．

Immunohistochemical staining is important for the differential diagnosis of basaloid squamous cell carcinoma（BSC）and other similar carcinomas, such as small-cell carcinomas and large-cell neuroendocrine carcinomas. p40 is a useful marker of squamous cell carcinoma that can be used for the diagnosis of BSC. We present the case of a 64-year-old man who was referred to our hospital for investigation of an abnormal shadow revealed on chest radiography. Computed tomography（CT）revealed a 16×11 mm nodule in the left lung（S1＋2）, and a thoracoscopic left upper lobectomy was performed. Histologically, lobular pattern with peripheral palisading was observed and the immunohistochemical staining revealed the tumor cells to be positive for p63 and negative for both p40 and neuroendocrine markers, leading to the diagnosis of BSC.