Case report: Metastatic adenocarcinoma of the lung with filiform “ciliated” tumor cells in the cerebrospinal fluid

Occurrence of cilia on the cell surface is usually considered evidence of a non-neoplastic process. Rarely, ciliated malignant tumors cells have been reported in pleural and ascitic fluids from ovarian and endometrial adenocarcinomas, though not from the cerebrospinal fluid (CSF) in association with pulmonary adenocarcinoma. We now present a case report of a patient who initially presented with neurologic symptoms. A CSF specimen revealed atypical cells with peripheral cilia and some cytoplasmic pigment. Cytologic, morphologic, and immunohistochemical analyses established this to be a metastatic adenocarcinoma of pulmonary origin with metastases to the meninges, pelvis, and the vertebrae. Cilia are generally the antithesis of malignancy as their presence is considered to be evidence of proper regulation of the cell cycle within a well-differentiated cell. This case offers the first described example of malignant ciliated cells derived from a metastatic lung adenocarcinoma. An awareness of this unusual presentation should aid in diagnosis and management when similar situations are prospectively encountered.