title: Pineal parenchymal tumor of intermediate differentiation with cytologic pleomorphism.
abstract: We report a case of pineal parenchymal tumor in a 33-year-old man incidentally detected by radiological examination. The MRI showed an unhomogeneously enhanced, small tumor (approximately 1 cm in size) in the pineal region. A tumor specimen was obtained at endoscopic biopsy. Routine histology showed a highly cellular tumor characterized by a predominance of small cells showing high nuclear : cytoplasmic ratio and moderate nuclear atypia, pleomorphism including giant cells and an absence of pineocytomatous rosettes. Mitotic figures were rare (approximately 1 per 10 high-power fields). Tumor necrosis was not evident. Immunohistochemically, the neoplastic cells showed positivity for neural markers (neurofilament protein, synaptophysin) and pinealocyte-associated antibodies (PP1, PP5, PP6), but not for glial fibrillary acidic protein or S-100. The MIB-1 labeling index was relatively high (6.3%). Ultrastructurally, there was some evidence of pinealocytic differentiation, such as vesicle-crowned rodlets (synaptic ribbons) and paired twisted filaments in neoplastic cells. Thus, the tumor was confirmed as a pineal parenchymal tumor of intermediate differentiation by histology, immunohistochemistry and electron microscopy. This case indicates that marked cytologic pleomorphism can occur in pineal parenchymal tumors of intermediate differentiation.
authors.affiliation: Department of Human Pathology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan. achie@med.gunma-u.ac.jp
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sasaki
authors.forename: Keishi
authors.initials: K
authors.lastname: Horiguchi
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Nakazato
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor / Q000032:analysis; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology*; D002454:Cell Differentiation; D006801:Humans; D007150:Immunohistochemistry; D008279:Magnetic Resonance Imaging; D008297:Male; D046529:Microscopy, Electron, Transmission; D010870:Pineal Gland / Q000378:metabolism / Q000473:pathology*; D010871:Pinealoma / Q000378:metabolism / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor