Papillary tumor of pineal region presenting with leptomeningeal seeding

Abstract

Papillary tumor of the pineal region (PTPR) is a recently recognized and rare pineal tumor, presenting as a solitary mass with or without hydrocephalus. Here, we report a case of c-Kit expressing PTPR with leptomeningeal seeding. A 39-year-old woman presented with a 1-month history of headache and decreased visual acuity. MRI showed a large, 4 cm-diameter solid and cystic enhancing mass at the pineal region with associated ventriculomegaly. Smaller nodular lesions were also found at the pituitary stalk and bilateral internal acoustic canal (IAC). The leptomeninges were noted to be enhanced with gadolinium. Endoscopic third ventriculostomy and partial resection were performed. The specimen was small in quantity but nonetheless, revealed the typical features of PTPR, which were tumor cells with vacuolated cytoplasm forming a pseudopapillary architecture. The tumor cells were diffusely immunoreactive for vimentin, INI-1 and c-Kit, focally immunoreactive for neuronal specific enolase (NSE) and S100 protein but negative for cytokeratin, epithelial membrane antigen (EMA), synaptophysin and GFAP. Ultrastructurally, the tumor cells revealed variably-sized cytoplasmic vacuoles, intermediate filaments and villous cytoplasmic membrane. With these features, a diagnosis of PTPR was rendered. The lesions at the pineal gland and bilateral IAC were irradiated through gamma knife radiosurgery and a decrease in size of the lesions was noted on follow-up MRI. However, soon after, other lesions were also noted to develop along the adjacent sites. The case presented is proof that PTPR can disseminate to other sites distant from the original lesion. This case was a c-kit expressing PTPR, which might represent the more primitive nature of this tumor. Ultrastructural examination is useful to differentiate PTPR from other tumors of the pineal gland in addition to immunohistochemistry.