A case of pleomorphic adenoma arising in the upper lip

多形腺腫は唾液腺腫瘍の中で最も発生頻度が高い腫瘍である. 小唾液腺にも発生する多形腺腫の中であるが, 口唇に発生することはまれである. 今回われわれは口唇腺に発生した多形腺腫の1例を経験したので文献的考察を加えて報告する. 患者は52歳女性で, 上唇の腫瘤精査目的に当院皮膚科を受診し, 上唇良性腫瘍と診断され, 当科へ紹介され受診した. 左側上唇粘膜下に11×9 mm大の弾性硬, 可動性良好な腫瘤を認め, 全身麻酔下に摘出術を施行した. 腫瘍は被膜に包まれており, 周囲組織との境界は明瞭であった. 病理組織学的検査所見では, 腫瘍は薄い線維性被膜に覆われ, 大小の腺管構造とその周囲に筋上皮細胞の増殖, および軟骨様組織の形成を認め, 多形腺腫との診断であった. 術後1年6か月経過した現在, 口唇の機能的, 形態的異常はみられず, 腫瘍の再発は認めていない. 多形腺腫には悪性転化の報告もあり, 今後も注意深く経過観察を行う必要があると考えられる.
Pleomorphic adenoma is the most common type of salivary gland tumor. The lip is a rare site of onset for pleomorphic adenomas that occur in the minor salivary glands. Here, we report our experience in the treatment of a patient with pleomorphic adenoma of the labial gland along with a review of the literature.The patient was a 52-year-old female who was referred to our department after consultation at the dermatology department of our institution for detailed examinations of a mass in the upper lip and being diagnosed with a benign tumor of the upper lip. A firm, elastic, highly movable mass of 11 × 9 mm was found under the mucosa of the left upper lip, which was excised under general anesthesia. The tumor was surrounded by a capsule, and the boundary of the surrounding tissue was well-delineated. Histopathological examinations revealed a thin fibrous capsule, and the proliferation of myoepithelial cells and formation of cartilage-like tissue were observed in and around the large and small ductal structures. Consequently, the tumor was diagnosed as a pleomorphic adenoma. At present, 1.5 years after surgery, no functional and morphological abnormalities of the lip have been observed, and there has been no recurrence of the tumor. Since there have been reports of malignant transformation of pleomorphic adenomas, careful follow-up will be necessary in the future.