sessile serrated adenoma/polypから発生したと考えられる上行結腸癌の1例

Colon Cancer that Might Have Originated from a Sessile Serrated Adenoma/Polyp in the Ascending Colon, Report of a Case

要旨　患者は70歳代，女性．上行結腸に中心陥凹を伴う発赤調の隆起性病変を認め，正色調の平坦隆起が連続していた．NBI拡大観察では陥凹部は密度が疎で不規則な微小血管像を呈しており，平坦部分では微小血管を視認できなかった．クリスタルバイオレット染色後拡大観察では陥凹部に一致してVi型高度不整pitを認め，平坦部分はII型pitであった．HPまたはSSA/Pから発生したIIa＋IIc型SM深部浸潤癌と診断した．組織学的に高異型度高分化腺癌がSSA/Pと連続し，陥凹部の中心では髄様癌が粘膜下層まで浸潤していた．癌細胞の核におけるMLH1とPMS2の染色性が消失しており，MSI-highの癌であることが示唆された．

　A female in her seventies had a reddish depressed lesion with margin protrusion and surrounding flat elevation in the ascending colon. NBI magnifying image showed distorted and sparse microvessels in the depressed area and no irregular vessel in flat elevation. With crystal violet staining, irregular pit pattern was seen in the depressed area and regular asteroid pit pattern was demonstrated in the flat elevation. The resected specimen histologically revealed well differentiated adenocarcinoma continuing to SSA/P and medullary adenocarcinoma with deeper submucosal invasion in the central depression. Microsatellite instability was proved by immunostaining of MLH1 and PMS2.