胃の平滑筋芽細胞腫Bizarre Leiomyoblastomaの1例

Bizarre Leiomyoblastoma of the Stomach, a Case Report

　1960年Martinらは，円型細胞で核周囲に透明帯のみられる特異な細胞形態をとる胃の平滑筋肉腫をmyoid tumorという名称で初めて記載した．1962年Stout¹⁾は同様のbizarreな組織像を示す69例を報告し，それら一群の腫瘍をleiomyoblastomaと呼ぶことを提唱した．

　本症は比較的まれなものであり，予後は一般に良好であるが，ときに転移をおこすことがあるといわれ¹⁾²⁾⁵⁾，組織像とともに悪性度または予後という点でも興味深い．胃に原発することがもっとも多いが，胃以外にも小腸，後腹膜，子宮などに発生することがある．

　A bizarre leiomyoblastoma in a 22-year-old woman is reported. She was admitted because of epigastralgia and anemia. Upper gastrointestinal series demonstrated a deep niche on lesser curvature of the antrum. Gastroscopically, a large elevated lesion with deep ulceration on the surface was observed at the same site. Although gastric biopsy was negative for malignancy, a tentative diagnosis of submucosal malignant tumor was reached on upper G. I. series and gastroscopy. Partial gastrectomy with gastrojejunostomy was performed.

　Gross findings of the resected stomach showed a extraluminally growing, 6.5×7.5×4.5 cm tumor on the lesser curvature of the antrum. Deep ulceration was seen on the surface of the tumor. A large number of tiny abscesses were found in the anal peritumoral tissue. Microscopically, short spindle or polygonal cells with clear spaces around the nucleus were seen. Based on these microscopic findings, diagnosis of bizarre leiomyoblastoma were established.

　The microscopic structure and prognosis of this type of tumor is characteristic. The majority of them are benign, and our patient is also well and alive 30 months after operation. Some of them, however, would metastasize, and mitotic rate of the tumor is the best criterion for prognosis.