Papillary cystadenoma of the upper lip.

To the Editor: We found a rare case of oral papillary cystadenoma in a 53-year-old woman. The lesion appeared as a 0.5-cm–diameter, well-circumscribed, solid swelling at the upper lip mucosa (Fig. 1). The patient denied having a history of local trauma, and her medical history was not contributory. Surgical removal was the treatment of choice, and histologically, the specimen was characterized as a wellcircumscribed cystic nodule with a papillary intraluminal projection characterized by epithelial cells arranged in multiple microcystic spaces with proteinaceous fluid (Fig. 2A). The cystic spaces were lined by cuboidal and columnar cells with areas of oncocytic metaplasia (Fig. 2B). No lymphoid stroma was found, and there were no mitotic figures or cytologic atypia. The literature shows that papillary cystadenomas are common neoplasms in the appendix, ovary, and pancreas 1 but are extremely rare in the oral cavity, especially in the upper lip. Until this moment, only 4 cases in this location were described 2–5 (Table 1). Histologically, the lesions are characteristics and the presence of oncocytic cells is common, although the real significance of this differentiation is not fully understood. The major diagnostic challenge is to differentiate the lesion from cystadenocarcinoma because of the similar architecture of both neoplasms and the lack of atypia of cystadenocarcinoma. Differentiation of these tumor types depends largely on the identification of actual infiltration of salivary gland parenchyma or surrounding connective tissue by either cystic or solid epithelium in cystadenocarcinoma. 2,6 In the current study, no signs of malignant transformation were observed. We concluded that, although uncommon in the oral cavity, papillary cystadenoma should be included in the differential diagnosis of the nodular lesions located in the soft tissues, especially in the upper lip. In addition, an accurate histologic analysis is essential to avoid misdiagnosis and unnecessary treatments.