Primary Meningeal Rhabdomyosarcoma of the Spinal Cord of a Young Dog with Neuromelanocytosis and Multiple Cutaneous Neurofibromas.

A 7-week-old male black Labrador retriever puppy was presented for post-mortem examination following progressive hindlimb paralysis and multiple masses within the skin. A highly compressive and infiltrative intradural mass was found within the T9-T11 spinal cord. Microscopical and immunohistochemical analysis revealed features compatible with spindle cell rhabdomyosarcoma (RMS). The adjacent spinal cord had numerous melanin-containing cells, arranged in small nodules, predominantly within the grey matter (proposed term of 'micronodular neuromelanocytosis') and the left lateral thorax had multifocal dermal neurofibromas. In this case, the constellation of proliferative/neoplastic lesions represents a unique case presentation with unclear aetiology. Primary canine meningeal RMS of the spinal cord has not been reported previously and represents a novel differential diagnosis for spinal tumours of young dogs. Moreover, such cases should be assessed for the presence of additional congenital abnormalities.