大腸腺癌の病理診断

Pathological Diagnosis of Colorectal Adenocarcinoma

要旨●早期大腸癌の治療は現在，内視鏡切除が主流である．内視鏡切除標本の病理診断には，病変が腺腫か腺癌かのみならず，pT1癌追加治療の要否につながるリンパ節転移危険因子〔①粘膜下層の浸潤距離（SM浸潤度），②低分化腺癌，印環細胞癌，粘液癌，③簇出，④脈管侵襲〕の正確な評価が求められる．本邦における腺腫と高分化管状腺癌の診断基準は，“浸潤”ではなく“異型度”であり，pT1癌においてSM浸潤度は，重要な危険因子の一つであるが，SM浸潤度の基準値1,000μmについてはその測定法や基準値の値そのものについてもいまだ議論の余地が残る．簇出や脈管侵襲についても診断する病理医間で均てん化が望まれるところであり，臨床医にも知っておいてもらいたい．

　Endoscopic resection is currently the first-line treatment for early-stage colorectal cancer. Accurate pathological assessment of endoscopically resected specimens is essential not only for distinguishing between adenoma and adenocarcinoma but also for evaluating the following risk factors for lymph node metastasis, which impact the need for adjuvant therapy in patients with pT1 cancer：①depth of submucosal invasion ; ②presence of poorly differentiated adenocarcinoma, signet ring cell carcinoma, or mucinous carcinoma ; ③budding/sprouting ; and ④lymphatic and/or venous infiltration. In Japan, the diagnostic criteria for adenoma and well-differentiated adenocarcinoma are based on cytological atypia rather than invasion. Although the depth of submucosal invasion is an important risk factor in pT1 cancer, debate remains regarding both the measurement method and the threshold for submucosal invasion depth（1,000μm）. Consistency in diagnosing budding/sprouting and vascular invasion among pathologists is also desirable, and clinicians should be aware of this aspect.