OBJECTIVE AND IMPORTANCE: Oncocytoma in the central nervous system is extre
mely unusual. The first reported example of oncocytoma in a melanocytoma of
the spinal cord was successfully excised, and its pathological appearance
is described.
CLINICAL PRESENTATION: A 71-year-old woman presented with a 25-year history
of back pain and myelographic evidence of a lumbar spinal cord mass. After
declining surgical treatment for two decades, she elected eventually to ha
ve the mass excised. Preoperative magnetic resonance imaging revealed a lar
ge intraspinal mass that spanned spinal levels L3 through S1.
TECHNIQUE: The mass was excised en bloc through posterior laminectomies, an
d histopathological analysis revealed a benign neoplasm composed predominan
tly of monotonous sheets of plump oncocytes. Electron microscopy confirmed
that the cytoplasm of the oncocytes was packed full of mitochondria. Focal
areas of the tumor contained spindle cells, with abundant intracytoplasmic
granular deposits of brown melanin pigment that contained melanosomes. Posi
tive Fontana-Masson, HMB-45, and S-100 staining confirmed the final diagnos
is of melanocytoma, oncocytic variant.
CONCLUSION: The first reported case of oncocytoma arising in spinal melanoc
ytoma is described. After surgical excision, the patient recovered complete
ly and has remained free of symptoms for 4 years.