Paraneoplastic Opsoclonus-MyoclonusSyndrome Associated with Malignant FibrousHistiocytoma: Neuropathological Findings

Overview

Paraneoplastic syndromes related to soft tissue tumors are very uncommon and an association ofparaneoplastic diseases with a malignant fibrous histiocytoma (MFH) has not been reported sofar. Opsoclonus-myoclonus is a rare paraneoplastic nervous system syndrome, that was well documentedin adult patients with neoplasms particularly of the lung and breast.A 77-year-old woman developed typical opsoclonus-myoclonus syndrome and rapidly progressedto coma. The opsoclonus and generalized myoclonus continued until the patient’s death sevenmonths later. An autopsy examination identified a pleomorphic MFH in the retroperitoneumwithout a metastatic spread. Microscopic examination of the cerebellum revealed an atrophy ofthe granular layer along with a marked patchy loss of Purkinje cells, and a loss of neurons in thecerebellar nuclei accompanied by distinct peridental demyelination and astrogliosis. A moderateloss of neurons and neuronal chromatolysis were observed also in the inferior olivary nuclei.However, the omnipause neurons of the nucleus raphe interpositus, that are supposed to beresponsible for opsoclonus generation under pathological conditions, as well as ocular brain stemnuclei were all intact.We failed to prove the presence of known antineuronal anti-Yo, anti-Hu or anti-Ri autoantibodiesin both serum and cerebrospinal fluid (CSF) of the patient. However, the confirmation of theintrathecal IgG synthesis by oligoclonal bands in CSF and the immunohistochemical detection ofIgG deposits on membranes of Purkinje cells, neurons of cerebellar granular layer and in cerebellarnuclei in our case support the presumed autoimmune nature of the disease.

Key words:
opsoclonus-myoclonus -⁠ paraneoplastic syndrome -⁠ malignant fibrous histiocytoma -cerebellum