Recurrent ameloblastoma as a granular cell variant 41 years after extirpating follicular tumor: Report of a case

We report a case of a granular cell ameloblastoma appeared 41 years after extirpation of a follicular type ameloblastoma. A 42-year-old woman underwent segmental resection of the right side of her mandible without mandibular reconstruction in 1964. The postoperative course has been uneventful until an otorhinolaryngologist found her right cheek swollen and referred her to us on February in 2005. A fine needle aspiration biopsy revealed the presence of granular cells in the sample. As the radiographic feature implied the recurrence of the previous ameloblastoma, we removed the lesion. The enucleated tumor (4.5 cm × 3.2 cm × 3.3 cm) was a cystic lesion that was encapsulated by a brown fibrous tissue and contained serous fluid. Microscopically, the lesion contained tumor nests consisted of numerous granular cells and some stellate cells, and each nest was surrounded by tall columnar cells. Immunohistochemistry for Ki-67, CD68, α1-antichymotrypsin, cytokeratin, S-100 protein, and p53 was performed on the specimens from both the primary and the recurrent lesions: the incidence of Ki-67-positive nuclei in the recurrent lesion was 5.1%, while that in the primary lesion was 0.5%. Besides, positive signals of both CD68 and α1-antichymotrypsin, indicative of phagocytosis, were broadly localized within tumor cells in the recurrent lesion. Taken these observations together, we assume that the extremely low proliferative potential of the primary tumor cells together with change to granular cells related to apoptosis might cause the tardy growth of the recurrent tumor after the initial tumorectomy.