胃の良・悪性境界領域病変の経過と生検組織診断

Histopathological Study of Benign/Malignant Borderline Lesion of the Stomach and its Biopsy Specimen

要旨　胃の良・悪性境界領域病変8例について，生検組織標本を含め病理組織学的に検討した．境界領域病変とは可能な限り上皮性腫瘍を良・悪性に振り分けた際に生ずる狭義の領域である．その肉眼形態は表面隆起型がほとんどであり，腫瘍径も1cm以下と，良性腺腫と同様な所見であり，また，早期癌の中には肉眼的に判別し難いものも少なくないことから，組織学的に判定される病変である．組織学的には腺管の構造異型はわずかであり，腫大した楕円形核あるいは小型円形核が不規則に配列する細胞異型が主体の組織所見である．境界領域病変の組織診断には良・悪性を判別する組織学的診断基準の確立が必要であるが，生検組織標本と切除標本の組織学的検討からは，Group分類はGroupⅢが明らかな良性腺腫に，そしてGroupⅣが境界領域病変に対応するような異型度判定に定義を変える必要性が示された．また，2例の経過観察例はいずれも発育進展が緩徐であるが，経過中の生検標本の組織異型度は早期癌のそれと比べると，良性腺腫よりは悪性に近い病変と考えられた．治療はその病像を熟知したうえで最良の方針を選択すべきであるが，そのためには生検組織診断の報告は異型度判定だけでなく，質的診断が臨床医と病理医との間で交わされることが必要である．

　The borderline lesions are defined as undetermined lesions in the narrow sense when epithelial lesions are divided into benign and malignant lesions. We evaluated 8 gastric benign/malignant borderline lesions ineluding biopsy specimens histopathologically. Most of the borderline lesions were the elevated type, less than 1 cm in size, and resembled benign adenomas macroscopically. It was difficult to distinguish them from small mucosal cancer macroscopically, therefore they were diagnosed by histological examination. Their structural atypia of the gland were slight, but enlarged oval shaped or small round shaped nuclei were arranged irregularly; cytological atypia was main histological findings. Two cases of borderline lesions have been followed and both of them have grown slowly. Histological examination of the biopsy specimen showed that they were close to early gastric cancer compared to benign adenoma.

　We need to develop histological diagnostic criteria to distinguish benign from malignant lesions, our microscopic study of the biopsy and resected specimens suggested that the current group classification needed to be modified as follows: Group Ⅲ should correspond to clearly benign adenoma and Group Ⅳ should be equivalent to borderline lesions.

　The best treatment option should be selected after the nature of the lesion is investigated, therefore, not only degree of atypia but quality of the lesion should be discussed between clinicians and pathologists.