Abstract
Background : Mixed squamous cell and glandular papilloma (mixed papilloma) is an extremely rare neoplasm. We report two cases of mixed papilloma with a focus on their cytology.
Cases : Both cases were women with a tumor in the peripheral region of the lung. On cytology, clumps of atypical squamous cells containing mucin in the cytoplasm were noted. Numerous keratinized atypical squamous cells were scattered in the background. In addition, glandular structures forming a tall columnar epithelium were noted ; the cells therein had brush borders or cilia. In both cases, the atypia of the tumor was mild. These cytologic features suggested a diagnosis of mixed papilloma. The glandular structures devoid of goblet cells excluded a diagnosis of non-neoplastic lesion, and the brush borders or cilia excluded a diagnosis of low-grade mucoepidermoid carcinoma. The histology confirmed the diagnosis of mixed papilloma. Immunohistochemically, the tumor cells were positive for CEA, p63, and MUC4.
Conclusion : Mixed papilloma have distinct cytological characteristics that are useful for the diagnosis of the tumor. Also, our immunohistochemical findings suggested that the glandular component was the primary lesion of the tumor, and that the squamous component may be the secondary lesion due to squamous metaplasia of the glandular cells.
