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Pineal parenchymal tumor of intermediate differentiation with cytologic pleomorphism
Atsushi Sasaki1, Keishi Horiguchi, Yoichi Nakazato
1Department of Human Pathology, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan. achie@med.gunma-u.ac.jp
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.
Insights
This case study highlights a pineal parenchymal tumor diagnosed via endoscopic biopsy. The findings demonstrate that significant cell variation can occur in these intermediate-grade tumors.
Area of Science:
- Neuropathology
- Oncology
- Neuroimaging
Background:
- Pineal parenchymal tumors (PPTs) are rare neoplasms arising from the pineal gland.
- Accurate diagnosis and classification are crucial for patient management and prognosis.
- Intermediate-grade PPTs can exhibit diverse histological features, posing diagnostic challenges.
Purpose of the Study:
- To report a case of pineal parenchymal tumor with unusual cytologic pleomorphism.
- To characterize the histological, immunohistochemical, and ultrastructural features of this tumor.
- To emphasize the potential for significant cellular atypia in intermediate PPTs.
Main Methods:
- Magnetic Resonance Imaging (MRI) for initial detection and characterization.
- Endoscopic biopsy for tissue acquisition.
- Routine histology, immunohistochemistry (IHC), and electron microscopy (EM) for detailed tumor analysis.
Main Results:
- MRI revealed a small, unhomogeneously enhancing lesion in the pineal region.
- Histology showed a highly cellular tumor with small cells, nuclear atypia, and pleomorphism including giant cells.
- Immunohistochemistry confirmed neural and pinealocyte markers, with a high MIB-1 labeling index (6.3%).
- Electron microscopy demonstrated features of pinealocytic differentiation.
Conclusions:
- The tumor was confirmed as a pineal parenchymal tumor of intermediate differentiation.
- This case illustrates that marked cytologic pleomorphism can be a feature of intermediate-grade PPTs.
- Comprehensive diagnostic methods are essential for accurate PPT classification.
