Pulmonary papillary adenoma-like tumour arising in ovarian teratoma.

papillary adenoma of the lung is a rare benign neoplasm composed of cuboidal cells with features of type II pneumocytes or Clara cells (1). Here we report a pulmonary papillary adenoma (PPA) arising in a mature cystic teratoma of the ovary. The patient, a 59-year-old woman, was found to have a cystic tumour in the right ovary. The patient had a family history (mother and one sibling) of ovarian cancer, and a bilateral ovariectomy was performed. Grossly, the right ovary was 3 cm in major axis. On cut section, it appeared completely transformed in a multi-cystic tumour. The cysts had a smooth inner surface and a mucoid content. The tissue between the cystic walls was thick and fibrous in appearance. The left ovary was unremarkable. Histologically, the cystic tumour had typical features of mature teratoma. Most of the cysts were lined by colonic type epithelium (Fig.1a), and in limited tracts by squamous and respiratory epithelium . A focus of solid nests composed of ovoid cells with coffee bean nuclei, consistent with a small Brenner tumour, was also present adjacent to a cyst (Fig.1b). In addition, one of the cysts showed a papillary proliferation abutting within the lumen. The lesion was 0.4 cm in its major axis and was constituted by anastomosing papillae bordered by cuboidal cells investing a fibrovascular core containing lymphoplasmacytic elements (Fig.2a). The cells lining the papillae had a moderate amount of cytoplasm and regular ovoid nuclei, with occasional nuclear eosinophilic inclusions (Fig.2b). Focally the lining cells were columnar ciliated cells reminiscent of respiratory epithelium. Anti-surfactant, anti-cytokeratin 7 and anti-TTF1 antisera stained most of the cells lining the papillary structures (Fig.2c), indicating a type II pneumocyte differentiation. Anti-thyroglobulin antibody was negative while CDX2 and cytokeratin 20 antisera stained the columnar cells showing colonic differentiation. Therefore it appears that the papillary structure of the lesion, together with the epithelium showing histological and immunocytochemical features of type II pneumocytes are consistent with a PPA arising in a mature ovarian teratoma. To the best of our knowledge, there are no similar cases reported in literature. Papillary lesions arising in ovarian teratomas are mainly represented by struma ovarii with foci of papillary thyroid carcinoma (2) which is histologically similar to PPA. However PPA usually lacks optically clear nuclei and atypia, and finally, its positivity for surfactant antibody can easily cast any doubt as this is not expressed in thyroid lesions.