食道類基底細胞癌における組織像の多彩性について

Wide Histological Spectrum of Basaloid Squamous Cell Carcinoma of the Esophagus

要旨　極めてまれな食道悪性腫瘍として知られる食道類基底細胞癌（BSC）は近年報告例が散見されるようになった．以前は低分化型扁平上皮癌や未分化癌と診断されることも多かったが，BSCの概念が一般的になってきた昨今，報告が増加してきた．しかしながら，いまだにこのBSCは食道腺様嚢胞癌（ACC）との鑑別が困難で，組織像に共通点が多いために混同されているのが現状である．われわれは36例のBSCを経験し，その組織像について検討した．BSCの病理像は極めて多彩で，画一的な定義付けは困難である．このような多彩性は，本腫瘍が扁平上皮・基底細胞・食道腺の導管・食道腺への分化を示すためと考えられる．われわれはこの多彩な組織像を大きく5つのcomponentに分けて，本腫瘍がこれらの組み合わせから成っていると考えた．ACC類似の像を呈するcomponentは食道腺への分化を示すもので，このことからACCは食道腺へ分化した，BSCの部分像であると考えた．

　Recently, reports of basaloid squamous cell carcinoma (BSC), which is an extremely rare malignant tumor of the esophagus, have been gradually increasing. Although this tumor used to be diagnosed as poorly differentiated squamous cell carcinoma or undifferentiated carcinoma, recently, the histological concept of basaloid squamous cell carcinoma of the esophagus has been recognized.

　However, because of the similarity of histological features, histological diagnosis has been confused with adenoid cystic carcinoma (ACC).

　In this study, we examined histological features of 36 cases of BSC and found that BSC is a histologically wide-spectrum tumor with various features, such as solid nest, microcystic and trabecular arrangement, duct-like structure, cribriform pattern and SCC component in the invasive area. Moreover, most of the tumors demonstrate intraepithelial squamous cell carcinoma.

　None of cases composed only of ACC (cribriform) pattern could be found, and all of the cases showed histological features with various components. We suggest that BSC originates from SCC and shows various differentiations towards basaloid cells, the esophageal duct and esophageal glands in the invasive area.