咽頭表在性扁平上皮癌に対する病理組織学的診断の課題

Problems to Be Solved in Pathological Diagnosis of Superficial Squamous Cell Carcinoma of Pharynx

要旨●扁平上皮乳頭層の毛細血管（IPCL）を描出する狭帯域内視鏡検査（NBI）が利用されるようになり，頭頸部領域において早期の表在性扁平上皮癌が検出されるようになって久しい．発声や嚥下といった生理機能を保持する治療は多大なる恩恵をもたらす一方で，完全切除がなされても低頻度ではあるもののリンパ節転移を来す症例も存在する．解剖学的に粘膜筋板のない頭頸部領域では，食道をはじめとした粘膜筋板が存在する，壁構造を細分類することが可能な臓器のように層構造別にリンパ節転移の頻度を提示することはできない．代用として，tumor thicknessが用いられている．加えて，「TNM分類 第8版」では，中咽頭癌および原発不明癌についてはHPV関連か否かについての判定が病理組織学的診断に求められている．治療指針の決定に関係する咽頭における病理組織学的診断についての課題を概説する．

　NBI（Narrow band imaging）for visualizing IPCL（intra-papillary capillary loops）has enabled discovery of superficial SCC（squamous cell carcinoma）of the head and neck at early stage, and preservation of physiological functions such as voice and swallowing, the latter being an innovation in treatment for SCC of HN（head and neck）. However, there are patients in which lymph node metastasis occurs infrequently, therefore, several problems that need to be addressed regarding management of superficial HNSCC 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 superficial HNSCC specimens. In head and neck, 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 head and neck cannot be subdivided into sublayers that could provide important information concerning risk of late lymph node metastasis, as is possible for the esophagus. In addition, in the 8th edition of the TNM classification, pathological diagnosis is required to determine whether oropharyngeal cancer and cancer of unknown primary are HPV（human papilloma virus）-associated or not. Several problems are yet to be resolved for handling of superficial HNSCC.