Pineal gland lesions are rare, with only a few cytologic descriptions occurring in the literature, according to the authors' knowledge. The current article describes the cytopathologic characteristics of 20 such lesions with discussion of differential diagnoses.
Cytologic material was obtained either by fine-needle aspiration biopsy (FNAB) under stearotactic radiologic guidance or by touch imprinting (TI) at the time of frozen sectioning. The 20 specimens include pineoblastoma (five specimens), pineocytoma (four specimens), astrocytoma (three specimens), germ cell tumor (three specimens), meningioma (one specimen), epidermoid cyst (three specimens), and pineal cyst (one specimen). Smears were stained with Diff-Quik and with Papanicolaou and hematoxylin and eosin stains. In selected specimens, immunoperoxidase (IPOX) stains were performed on cell block sections using synaptophysin, neuron-specific enolase, placental alkaline phosphatase, glial fibrillary acidic protein, leukocyte common antigen, cytokeratins, and human chorionic gonadotropin antibodies.
Several cytomorphologic characteristics unique to each lesional category with occasional overlapping features were observed. The unique features included the following: small, hyperchromatic, round to oval cells with frequent rosetting (pineocytoma), with a few specimens in addition showing hypercellularity, crowding, mitoses, and necrosis (pineoblastoma); pleomorphic round cells in a fibrillary background (astrocytoma); large polygonal cells with prominent nucleoli and clear cytoplasm (germ cell tumor); spindled fibroblastic cells (meningioma); anucleate squames and mature squamous cells (epidermoid cyst); and small uniform polygonal cells (pineal cyst). When necessary, IPOX studies supported the morphologic diagnoses.
FNAB and TI cytology were found to provide a rapid and reliable diagnosis of pineal lesions. This is particularly important when dealing with minute amounts of tissue material. Both techniques appeared to provide equally good cytomorphology on smears. IPOX studies played an important complementary role in difficult cases when performed on cell blocks.