小腸悪性腫瘍の病理学的特徴―悪性リンパ腫

Malignant Lymphoma of Small Intestine

要旨　小腸悪性リンパ腫は，全消化管悪性リンパ腫のうち20～30％を占め，小腸悪性腫瘍の中では癌およびGISTと並んで頻度の高い腫瘍の1つである．今回，筆者らは小腸悪性リンパ腫の外科的切除標本43例を用いて，肉眼形態と組織型の傾向について検討した．平均年齢63.2歳で男性30例，女性13例と男性に多かった．また，回腸末端発生の10例を含む回腸発生例が36例（84％）と，空腸発生7例（16％）に比べて有意に多かった．肉眼形態は，潰瘍型が35例（81％）と最も多かった．組織型別にみると，びまん性大細胞型B細胞性リンパ腫（DLBCL）が24例（56％）と最も多く，うち22例が潰瘍型であった．43例中38例（88％）が壁全層あるいは隣接する他臓器へ浸潤しており，壁構造を破壊しながら増殖するリンパ腫細胞により，潰瘍あるいは隆起を形成すると考えられた．ほとんどの組織型で粘膜深層から増殖する粘膜内のリンパ腫細胞を認め，EATLのように粘膜固有層全層に増殖浸潤し，側方にびまん性に拡がる組織型もあった．このように小腸悪性リンパ腫は，組織型あるいはその組織学的悪性度によりさまざまな肉眼形態を示すと考えられた．

　Primary small intestinal lymphoma is a relatively common in primary small intestinal malignancy, like carcinoma or GIST（gastrointestinal stromal tumor）. The occurrence of it is about 20～30％ of primary gastrointestinal malignant lymphoma. In this study, we reviewed 43 surgically resected small intestinal lymphomas, and find the macroscopic or histological feature of primary small intestinal lymphoma.

　The primary lesions within the ileum were observed in 36 cases（84％）, and in 7 cases（16％）they occurred in the jejunum. The average age of people who undergo an operation is 63.2 year-old（range 23 to 86 year-old）. Thirty males and 13 females were operated.

　Macroscopically, the ulceration type is most frequently seen in 35 cases（81％）in this study. Twenty-four cases（56％）are revealed as DLBCL（diffuse large B-cell lymphoma）, and of them 21 cases are classified within the ulceration type．

　In thirty-eight out of 43 cases（88％）, the lymphoma cells are involving the whole thickness of small intestine or invading the neighbor organs, and are revealed as ulcerative or elevated mass lesions. In most cases, lymphoma cells are proliferating within the deep portion of the mucosa at the edge of the mass lesion. In the cases of EATL（enteropathy-associated T cell lymphoma）, lymphoma cells are proliferating within the mucosal laminar propria and widely spreading laterally. As above, ulceration type can be said“common”, but other various macroscopic features are observed in the primary small intestinal lymphoma depending on the histological phenotype．