食道SM癌の悪性度評価に有用な病理学的因子—Tumor buddingのリンパ節転移予測因子としての有用性を中心に

Histopathological Factors for Evaluation of the Malignant Potential of Esophageal T1b-SM Squamous Cell Carcinoma：Tumor Budding as a Predictive Factor of Nodal Metastasis

要旨●食道SM扁平上皮癌において，リンパ節転移予測を含む悪性度の病理組織学的評価は重要である．これまでに病理学的なリンパ節転移予測因子として深達度，脈管侵襲に加え，細胞異型，分化度，微小胞巣形成などが提唱されてきた．中でも微小胞巣形成は“tumor budding”という呼称とともに，その重要性や評価方法についてのコンセンサスが形成されてきた．今回筆者らは，食道表在癌におけるtumor buddingのリンパ節転移予測因子としての有用性とともに，適切なカットオフ値および上皮細胞の免疫染色の有用性について明らかにした．最後に食道扁平上皮癌の治療方針決定のために利用される可能性のある分子病理学的変異について概説する．

　Histopathological evaluation of malignant potential, including prediction of lymph node metastasis, is important in cases of T1b-SM esophageal squamous cell carcinoma. To date, a number of pathological predictors of lymph node metastasis have been proposed, namely, depth of invasion, vascular invasion, cellular atypia, degree of differentiation, and infiltrating proliferation with small cancer cell cluster formation. Of these putative predictive factors, the formation of small cell clusters, known as “tumor budding”, has received considerable attention, with a consensus being reached regarding its predictive importance and standardization of a reliable evaluation approach.

　In this study, we show the usefulness of tumor budding as a predictor of lymph node metastasis in superficial esophageal cancer by establishing appropriate threshold values and demonstrating the advantage of immunostaining cancer cells. Further, we outline the potential application of molecular alterations known in esophageal squamous cell carcinoma for the evaluation of malignancy.