Cytologic features of papillary tumor of the pineal region: A case report showing tigroid background.

Papillary tumor of the pineal region (PTPR) is a rare neuroepithelial tumor of the pineal region of adults. We herein describe on a 34-year-old female the cytologic features of a PTPR studied using Diff-Quik stain. The patient presented hydrocephalia secondary to a pineal tumor. During surgery an intraoperative pathologic consultation was requested. Smears were hypercellular with numerous papillary tissue fragments and single cells. Papillary fragments had an evident inner vascular core. Neoplastic cells displayed moderate pleomorphism, plasmocytoid morphology, and cytoplasmic fragility. The background had a foamy, lace-like, tigroid appearance. Pathologic analysis revealed morphologic and immunohistochemical features of PTPR. When evaluating smears of a pineal tumor in an adult, the presence of true papillary structures and numerous single cells should raise the possibility of PTPR. This is particularly useful during intraoperative pathologic evaluation since, on frozen sections, the epithelial morphology of the tumor may be misleading. The papillary morphology which gives name to this neoplams is best appreciated on squash smears. An interesting feature seen in the present case was a prominent tigroid background. This is a characteristic cytologic feature observed in Romanowsky-type stained smears of germinoma and related tumors. It can be seen in other clear cell, glycogen-rich tumors. PTPR shares with these neoplasms its clear cell morphology and PAS positive cytoplasmic granules. As seen from the present case, germinoma is not the only tumor of the pineal region that may show a tigroid background. Cytologic features of PTPR differ from those of germinoma allowing their distinction during intraoperative consultations. Diagn. Cytopathol. 2016;44:1098-1101.