咽頭表在性扁平上皮癌の病理

Pathology of Superficial Type Squamous Cell Carcinoma of the Pharynx

要旨●NBI（狭帯域内視鏡）の開発は，咽頭における表在性扁平上皮癌の発見と発生および嚥下という重要な生理機能を温存することを可能にする大きな治療革新を起こした．このように縮小切除が施行された患者の経過が明らかになっていくにつれて，表在癌に対して解決すべき課題が突きつけられるようになった．その一つは，縮小切除後のリンパ節郭清といった追加治療の可否を病理組織像から予測可能か否かである．咽頭癌では，粘膜筋板がないために壁深達度の概念はT因子に含まれておらず，広い上皮下層を細分類してリンパ節転移に関するリスクを食道癌のように段階別に表示できない．そのため，咽頭癌ではtumor thicknessを壁深達度に代わる組織学的因子として用いている．本稿では表在癌が抱える問題を解説する．

　The emergence of NBI（narrow band imaging）for visualizing IPCL（intra-papillary capillary loop）has enabled discovery of superficial type SCC（squamous cell carcinoma）of the pharynx and preservation of physiological functions such as voice and swallowing, the latter being an innovation in treatment for pharyngeal SCC. However, since the clinical courses of patients who have undergone reduction resection of pharyngeal SCCs have been published, several problems that need to be addressed regarding management of pharyngeal SCC have become apparent. One such problem concerns determination of the necessity for additional dissection of lymph nodes on the basis of pathological findings in resected pharyngeal SCC specimens. In pharyngeal cancer, the pathological T factor does not include the concept of depth of invasion because of absence of the muscularis mucosae ; thus, the wide subepithelial layer of pharynx cannot be subdivided into sublayers that could provide important information concerning risk of late lymph node metastasis, as is possible for the esophagus. Tumor thickness has been used as an alternative means of determining risk of lymph node metastasis from pharyngeal SCC ; however, several problems are yet to be resolved.