Paraneoplastic opsoclonus-myoclonus syndrome associated with malignant fibrous histiocytoma: neuropathological findings.

Paraneoplastic syndromes related to soft tissue tumors are very uncommon and an association of paraneoplastic diseases with a malignant fibrous histiocytoma (MFH) has not been reported so far. Opsoclonus-myoclonus is a rare paraneoplastic nervous system syndrome, that was well documented in adult patients with neoplasms particularly of the lung and breast. A 77-year-old woman developed typical opsoclonus-myoclonus syndrome and rapidly progressed to coma. The opsoclonus and generalized myoclonus continued until the patient's death seven months later. An autopsy examination identified a pleomorphic MFH in the retroperitoneum without a metastatic spread. Microscopic examination of the cerebellum revealed an atrophy of the granular layer along with a marked patchy loss of Purkinje cells, and a loss of neurons in the cerebellar nuclei accompanied by distinct peridental demyelination and astrogliosis. A moderate loss 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 be responsible for opsoclonus generation under pathological conditions, as well as ocular brain stem nuclei were all intact. We failed to prove the presence of known antineuronal anti-Yo, anti-Hu or anti-Ri autoantibodies in both serum and cerebrospinal fluid (CSF) of the patient. However, the confirmation of the intrathecal IgG synthesis by oligoclonal bands in CSF and the immunohistochemical detection of IgG deposits on membranes of Purkinje cells, neurons of cerebellar granular layer and in cerebellar nuclei in our case support the presumed autoimmune nature of the disease.