Acinic cell carcinoma found by recurrence of a mucous cyst in the sublingual gland.

This case report describes an acinic cell carcinoma found by a recurrence of a ranula in the sublingual gland. A 42-year-old male was admitted to the hospital of the Tokyo Dental College with a swelling in his right oral floor but without pain. The lesion was treated by windowing the same day under the diagnosis of a ranula, but the swelling appeared again at the same area eight months after the first operation. A resection was performed, and the specimen was sent to the clinical laboratory for pathological diagnosis. Proliferating serous cells were seen in part of the wall of an exudative mucous cyst. PAS staining was partially positive, and immunohistochemical staining for S-100 protein, lactoferrin, and amylase were also positive in cytoplasmic granules. This report concludes that the pathological diagnosis is beneficial in clarifying the reasons for the recurrence of a benign lesion.