gms | German Medical Science

Objective: Numerous differential diagnoses are considered for patients presenting with intraspinal tumors. Intraspinal melanocytomas originating from leptomeningeal melanocytes are a very rare entity. Inconsistent appearances from magnetic resonance images can be misleading and make diagnosis uncertain. This may lead to poorer outcomes due to unexpected intraoperative complications and the need to change resection strategies.

Methods: This case series summarizes three histologically confirmed cases of melanocytoma, operated in our hospital between 2011-2015. A 50-year-old female with suspected intraspinal meningioma (1), a 16-year-old under investigation for ependymoma (2) and a 34-year-old with sensory deficits in his arm (3). Two patients presented with clinical signs of spinal cord compression and one case was an incidental finding on an MRI.

Results: For each case, intraoperative appearances differed from expectations (based on pre-surgical imaging) therefore adaptation of surgical strategies were necessary. In (1) the neoplastic tissue was amenable to complete excision despite partly invasive growth. However, new motor and sensory deficits presented postoperatively. In (2) the tumor could not be resected completely owing to risks to spinal cord perfusion. In (3) a transforaminally growing mass, expected to be a neurofibroma, appeared to be highly adherent to surrounding tissue, so complete excision was not possible without risking spinal stability. Further dermatological follow up-examinations were necessary to confirm the diagnosis of a melanocytoma, since neurological histologic results were inconclusive.

Conclusion: Intraspinal melanocytomas are difficult to diagnose due to their varying appearances in MR images. Usually they are benign in nature although malignant courses have been described in literature. Unexpected intraoperative findings such as invasive growth and adherence can lead to incomplete excision or new motor/sensory deficits that exceed pre-operative anticipations. Inconsistent appearances in sectional imaging may be reflected by inconclusive histological findings, leading to further costly investigations before a diagnosis can be confirmed. Despite their rare occurrence, spinal melanocytomas should be considered as a differential diagnosis in patients presenting with an intraspinal tumor in order to optimize surgical management.