胃のBizarre Leiomyoblastomaの1例

A Case Report of Bizarre Leiomyoblastoma of the Stomach

　胃にみられる非上皮性悪性腫瘍には，悪性リンパ腫がその約半数を占め，次いで平滑筋肉腫が多いといわれる．1962年，A. P. Stout¹⁾は，胃に発生した平滑筋腫瘍を検討し，その中で臨床的に良性経過をたどり，組織学的には腫瘍細胞が非常にbizarreな形態を呈するものを選んだ．これらの腫瘍は，従来neurogenous tumor，vascular tumorなどの範疇に入れられていたものであるが，これをBizarre Leiomyoblastomaと名付け，その組織学的特徴を述べた．本邦では，1965年に久保らが3例の同症例を報告²⁾して以来，第62回日本病理学会で田中らが発表した5例を含めても20例に足りない．今回，われわれは，26歳という若年の男性例を経験したので，組織学的特徴および電顕的所見を中心として，文献的検討も加え報告する．

症例

　患　者：26歳　男性　事務員

　既往歴・家族歴：特記すべきことなし

　主　訴：空腹時の心窩部重圧感と嘔気

　現病歴・入院時所見：1976年2月に主訴が増強したため来院．痩身だが，結膜の貧血などはない．また，主な臨床検査成績は，赤血球495×10⁴4白血球8,200，HB95％，血圧120～80であった．

　A case of the so-called bizarre leiomyoblastoma (Stout, 1962) of the stomach is presented. The patient was a 26 years old Japanese male, who revealed endoscopically and roentogenoscopically a large tumor in his stomach. The tumor was removed by 2/3 subtotal gastrectomy with Billroth Ⅱ, antecolica. Macroscopically there was a 2.5×2.0×2.0 cm tumor in the submucosa of the lesser curvature in the anterior wall of corpus, with a shallow ulcer in the center of the tumor. Microscopically, the tumor showed round or polygonal cells, having bizarre nuclei with abundant chromatin, and some characteristic perinuclear elear zone in the cytoplasm, intermingled with spindleshaped cells simulating smooth muscle cells. The tumor cells were at places arranged closely related to the vascular wall, and few mitosis could be encountered even when examined strictly. Electronmicroscopically, there were many mitochondria, well developed rEr. and several small dense bodies in their cytoplasm. Of the most interesting features encountered were abundant bundles of myofilament in the perinuclear cytoplasm,100 to 150 A. in width, and having prominent fine tubular structures and especially some remnants of periodic banded profils in the sarcoplasm, closely bound to the adjacent cells partially with desmosomes.

　From these observations described especially by electron microscopy we assume that this tumor, the socalled bizarre leiomyoblastoma, should more appropriately be designated as “bizarre myoblastoma of the stomach”, because of the fine myofilament including striated muscle-like bundles.