Pneumocytoma (sclerosing hemangioma), a potential pitfall.

Pneumocytoma is an uncommon benign tumor of the lung, derived from primitive respiratory epithelium, with a predilection for middle-aged females. A single, well-circumscribed mass is commonly identified on imaging, necessitating pathologic evaluation for further assessment. Fine-needle aspiration cytology is a minimally invasive and cost-effective method that can be utilized in the diagnosis of these lesions. Yet, distinction of pneumocytoma from other entities such as well-differentiated adenocarcinoma or carcinoid tumor can be quite challenging. Herein, we describe a case initially misdiagnosed as lung adenocarcinoma on FNA that was proven to be pneumocytoma on subsequent resection. This report highlights the importance of recognizing key cytologic features of pneumocytoma, namely the papillary architecture, dual cell population, and the hemorrhagic background with foamy macrophages, among others. An accurate preoperative diagnosis of this entity provides optimal patient management, as conservative surgical excision is curative. Diagn. Cytopathol. 2017;45:744-749. © 2017 Wiley Periodicals, Inc.