特殊組織型の食道癌―X線の立場から

Special Histopathologic Type of Esophageal Carcinoma (Non-Squamous Cell Carcinoma) : Point of View from the Radiological Findings

要旨　扁平上皮癌以外の特殊組織型を示す食道癌は極めてまれな腫瘍である．これまでに51例の扁平上皮癌以外の組織型を示す食道腫瘍を経験し，その内訳は類基底細胞癌15例，小細胞型未分化癌14例，癌肉腫8例，腺扁平上皮癌7例，腺様嚢胞癌2例，悪性黒色腫2例，粘表皮癌1例，そのほかカルチノイド1例，GIST1例であった．いずれも隆起を主体とする腫瘍が多く，X線診断では，①隆起の形状と高さ，②隆起の立ち上がり所見，③表面の性状，④周囲への上皮内進展の有無などを描出しなければならない．上皮下への進展を有する食道癌は扁平上皮癌においても経験されるが，表面平滑で急峻な立ち上がりを示す腫瘍では扁平上皮癌以外の食道癌，特に小細胞型未分化癌や腺様嚢胞癌を考えなければならない．一方，類基底細胞癌ではなだらかな立ち上がりを示す．また丈が高く表面が結節状で不整な病変は，癌胞巣の増殖に伴う形態変化であり，類基底細胞癌および小細胞型未分化癌いずれでも認められるが，扁平上皮癌とは異なり各結節の表面は平滑で，隆起間の溝の線もやわらかさを持っている．腺様嚢胞癌は，表面平滑な広基性隆起として描出されるのに対して，悪性黒色腫の隆起基部は狭く亜有茎性隆起を示す傾向にある．また特殊組織型の食道癌は，進行すると転移の可能性は扁平上皮癌よりも高い傾向にあり，これらの腫瘍の早期発見と診断は，予後を決定する大変重要な役割を担っている．

　Any special histopathologic type of esophageal carcinoma, that is non-squamous cell carcinoma is very rare. We have encountered 51 cases of non-squamous cell carcinomas, including 15 cases of basaloid carcinoma, 14 cases of undifferentiated small cell carcinoma, 8 cases of carcinosarcoma, 7 cases of adenosquamous carcinoma, 2 cases of adenoid cystic carcinoma, 2 cases of malignant melanoma and one case of mucoepidermoid carcinoma and two other tumors.

　Most of these tumors appeared as polypoid lesions and radiographic study should be carried out observing the shape and height of the tumors, their type of elevation, their surface configuration, and the intraepithelial tumor spread. Although some squamous cell carcinomas infiltrated mainly into the subepithelial layer, the protruding tumors covered with a smooth surface and a steep boarder of elevation were highly suggestive of non-squamous cell carcinoma, especially undifferentiated small cell carcinoma and adenoid cystic carcinoma. On the other hand, basaloid carcinomas were observed as ill-defined and having gradual elevation. Protruding lesions with nodular and irregular surface were produced by the proliferation of many cancer cell nests, and these lesions were suggestive of basaloid carcinoma and undifferentiated small cell carcinoma. Radiological findings of these tumors showed a smooth nodular surface and a gentle line of gutter between the nodules, differing from the findings in squamous cell carcinoma. While adenoid cystic carcinoma showed a broad-based tumor, malignant melanoma tended to be a semi-pedunculated lesion with a narrow base. The special histopathologic types of esophageal carcinoma in the advanced stage metastasize more easily than ordinary squamous cell carcinomas. So the early detection and diagnosis of these tumors plays an important role in determining prognosis.