Pulmonary papillary adenoma: a case report and review of the literature.

Pulmonary papillary adenomas are rare neoplasms that predominantly occur in the periphery of the lung. We describe a 24-year-old male with a 6.0-cm spherical mass found incidentally at the periphery of the left upper lobe by imaging. Enucleation of the neoplasm was performed with intraoperative frozen section analysis. The tumor histologically showed papillary proliferations containing fibrovascular cores lined by a single layer of tumor cells that lacked atypia, mitoses, or necrosis. The histologic features were consistent with a pulmonary papillary adenoma. Pulmonary papillary adenoma was previously considered to be a benign entity. However, because of its invasive growth pattern, it has been suggested that this neoplasm has intermediate malignant potential. The clinicopathologic features and differential diagnosis of this unusual neoplasm is discussed with a review of the English literature.