Objectives A sarcoid-like pathological reaction has been well described to occur in response to germ cell tumours of the testes, most commonly seminoma. This reaction has been seen both within the testes and sites of metastatic disease including the lungs and lymph nodes. There are very few preceding reports of seminoma metastasising to the central nervous system (CNS) and no cases have been reported of a neurosarcoid-like reaction to such metastases, nor distant sarcoidal reaction beyond sites of tumour cell metastasis.
Case A 29 year old male presented with seizures and an amnestic syndrome. CSF was inflammatory with raised mononuclear cells. MRI revealed left mesial temporal lobe and cerebellar peduncle hyperintensities. Investigations for viral and autoimmune limbic encephalitis were performed. Autoantibodies for limbic encephalitis were negative as was initial malignancy screen. The patient deteriorated despite treatment trials with steroids and intravenous immunoglobulin. Brain biopsy was performed and revealed non-necrotising epithelioid granulomas consistent with a histopathological diagnosis of neurosarcoidosis. A secondary screen for malignancy lead to a diagnosis of metastatic seminoma with involvement of the abdominal lymph nodes. There was no evidence of metastatic seminoma to the CNS on biopsy or non-invasive investigation.
Conclusions This case represents the first description of neurosarcoidosis developing as an antigen driven paraneoplastic phenomenon in the context of metastatic seminoma with an absence of CNS metastatic disease.