Pineocytoma and pineal parenchymal tumors of intermediate differentiation presenting cytologic pleomorphism: a multicenter study

Abstract

Cytologic pleomorphism has been described in a limited number of benign pineal tumors, namely pineocytoma (PC) and pineal parenchymal tumors (PPTs) of intermediate differentiation (PPTID). We examined the clinicopathologic features in a retrospective series of 14 cases (seven females and seven males aged from 10 to 65 years) of pleomorphic PPT. Seven cases were PC, with no mitoses and with areas of tumoral cells forming large pineocytomatous rosettes and other areas with giant cells containing hyperchromatic nuclei. The other seven were PPTID, presenting few mitoses (< or =2), a Ki67 proliferation index between 3% and 7%, and predominantly composed of small neoplastic cells and scattered giant cells, sometimes multinucleated. In the 14 tumors, the proportion of pleomorphic areas was variable. Most tumoral cells showed extensive neuronal differentiation with strong expression of neuron-specific enolase, synaptophysin and neurofilaments. Some of the neoplastic cells expressed S100 protein. The follow-up period ranged from 1.2 to 13 years and only one PC and one PPTID progressed after stereotactic biopsy or incomplete resection. The lack of invasiveness and the low proliferation index of these tumors suggest a benign clinical course despite the marked pleomorphism, the latter of which can lead to upgrading.

Figure 1

A. Sagittal T1‐weighted magnetic resonance imaging (MRI) scan in a patient with pleomorphic pineal parenchymal tumor (case 3). B. Sagittal T1‐weighted MRI scan in the same patient after gadolinium injection, showing homogeneous enhancement.

Figure 2

Light microscopic and immunohistochemical features of pleomorphic pineal parenchymal tumors (PPTs). A. Pleomorphic pineocytoma (PC) with pineocytomatous rosettes and giant cells with hyperchromatic nuclei (hemalin phloxine saffron staining). Inset: cytologic imprint of a pleomorphic PC showing tumoral cells with small round nuclei and larger cells with pleomorphic nuclei (toluidine blue staining). B. Pleomorphic PPT of intermediate differentiation (PPTID) with marked cytologic pleomorphism (hemalin eosin staining). Synaptophysin immuno‐labeling in a pleomorphic PC (C) and a pleomorphic PPTID (D). Expression of neurofilament in one pleomorphic PC (E) and in one pleomorphic PPTID (F), with intense labeling of giant cells. G. Chromogranin A labeling in a pleomorphic PC. H. CD34 labeling in a pleomorphic PC showing some positive giant cells. I. Nuclear and cytoplasmic S100 protein staining in giant cells of a pleomorphic PC. J. Areas of a pleomorphic PPTID showing nuclei stained for Ki67. Scale bars = 50 µm in A–I, 100 µm in J.