・ MIYAMOTO Ikuya 3 ) YADA Naomi 4 ) ・ KAWANO Michinao 5 ) ・ TOMINAGA Kazuhiro 1 ) : Atypical lipomatous tumor (ALT) is a relatively common soft tissue tumor, but it is extremely rare in the head and neck region, especially in the oral cavity. We report a case of tumor of the tongue that was considered a morphologically atypical lipomatous tumor. A 65-year-old woman was referred to our hospital with a mass on the right side of her tongue. Clinical examination revealed a well-demarcated, movable,

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... emarcated, movable, elastic-hard, and painless lesion, with a diameter of 15 × 15 mm. We made a provisional diagnosis of a benign tumor and performed an incisional biopsy. The pathological diagnosis was ambiguous, ranging from lipoma to ALT. An excisional biopsy was performed with the patient under local anesthesia with intravenous sedation. Microscopic examination revealed a well-circumscribed lesion, composed of proliferative fat cells with considerable variations in size and shape, as well as many multi-vacuolated lipoblasts. The final histopathological diagnosis was morphologically ALT. We surgically excised an additional 10 mm of the tissue surrounding the tumor with the patient under general anesthesia. The patient has remained free of recurrence and metastasis for 5 years after surgery. : atypical lipomatous tumor (異型脂肪腫様腫瘍) ,tongue (舌) 1) 九州歯科大学生体機能学講座顎顔面外科学分野 (主任:冨永和宏教授) 2) 医療法人渓仁会手稲渓仁会病院歯科口腔外科 (主任:関口 隆部長) 3) 岩手医科大学口腔顎顔面再建学講座口腔外科学分野 (主任:山田浩之教授) 4) 九州歯科大学健康増進学講座口腔病態病理学分野 (主任:松尾 拡教授) 5) 九州歯科大学生体機能学講座口腔内科学分野 (主任:吉岡 泉教授) 1)