Table of Contents

Washington University Experience | NEOPLASMS (PINEAL) | PPTID (Pineal Parenchymal Tumor Intermediate Differentiation) | 3E PPTID (Case 3) MIB

Ki67 (MIB-1 antibody) generally exhibits a proliferation index of 5.6%, but ranges focally up to 14.5%. ---- Not shown: Reactivity for neurofilament protein appears in only a small subset of scattered tumor cells. ---- Comment: This histological/immunohistochemical pattern describes pineal parenchymal tumor with intermediate differentiation (PPTID), pleomorphic variant. Reflecting the clinicopathological heterogeneity of and limited world-wide experience with PPTID, PPTID may be assigned a WHO grade of 2 or 3 but the criteria for making this distinction are not firmly established. Current consensus is supported by a large study that observed relatively worse outcome for tumors exhibiting only rare cells immunoreactive for neurofilament protein (consistent with loss of neural differentiation) or a mitotic index of 6 or more mitotic figures per 10 HPF. Therefore, acknowledging that immunohistochemical staining for neurofilament protein can be variable among laboratories, we nevertheless conclude that the constellation of focally increased mitotic index and minimal reactivity for neurofilament observed in this case warrant greater concern for an adverse outcome, and assignment of WHO grade 3.

---