A Rare Case of Embryonal Rhabdomyosarcoma of Pineal Gland in An Adult Male

Abstract

Abstract Introduction/Objective Rhabdomyosarcoma (RMS), mesenchymal derived tumor, is predominantly diagnosed in the pediatric population but may present at any age. Less than 1% of all adult solid malignant cancers are sarcomas, and rhabdomyosarcoma comprises <0.001% of adult sarcomas. Primary intracranial RMS is rare and has been reported in the cerebrum, cerebellum, brainstem, and the meninges. The occurrence of a primary intracranial RMS arising from the pineal gland is exceedingly rare. Methods/Case Report An adult male presented to the ED with complaint of several months of headaches, progressive confusion, forgetfulness and most recently difficulty in finding words. CT scan showed a large mass arising from the pineal gland causing obstructive hydrocephalus. Subsequently, the patient underwent excisional biopsy. The histopathology examination revealed small round basophilic cells and large polygonal cells with large eccentric nuclei and prominent nucleoli, abundant eosinophilic cytoplasm containing globular paranuclear eosinophilic inclusions, characteristic of rhabdoid cells. Immunohistochemical (IHC) showed tumor cells are positive for Desmin, MyoD1, CK8/18, INI1 (hSNF5; SMARCB1) with retained nuclear expression and faint positivity for Synaptophysin and focally positivity for Neurofilament. The tumor cells showed negative staining for Pankeratin, SOX10, Oct4, SALL4, INSM1, LCA AND CD30, which excluded the possibility of Germ cell tumor and Pineoblastoma. The case was finalized as primary malignant neoplasm, consistent with Embryonal Rhabdomyosarcoma of pineal gland. Results (if a Case Study enter NA) NA Conclusion This case highlights the rare occurrence of rhabdomyosarcoma originating from the pineal gland in an adult male. Morphologic and immunohistochemical findings were consistent with embryonal rhabdomyosarcoma. Since primary rhabdomyosarcoma of the pineal gland is rare, this case contributes to the limited body of literature on such cases. It underscores the importance of considering unusual entities in intracranial tumors. The distinct morphology and the use of IHC aids in diagnosing this rare entity.