Surgical management of melanotic schwannomas: a 28-year mayo clinic experience and comparative literature analysis

Introduction: Melanocytic schwannoma is a rare nerve sheath tumor characterized by neoplastic melanin-producing Schwann cells. We present our institution's experience treating spinal melanotic schwannomas and compare it to the literature.

Methods: Data were collected for eight patients treated surgically for spinal melanotic schwannomas between 1996 and 2022 at all Mayo Clinic locations and 63 patients in the literature. Time-to-event analysis showing the risk of metastasis, recurrence, and death by tumor location and type of treatment received was created for all 71 cases combined. Unpaired two-sample t-tests and Fisher's exact tests assessed statistical significance between groups.

Results: Eight patients with melanotic spinal schwannomas underwent surgery between 1996 and 2022 at our institution, while we found 63 patients surgically treated in the literature. Our patients and those in the literature experienced a similar age at diagnosis (43 y vs. 43.09 y., respectively). At our institution, 2 cases had metastasis, five patients had a long-term recurrence, and five patients died, while in the literature, 16 patients had metastasis, 23 had a recurrence, and 13 died. Time-to-event analysis curves for all 71 patients showed a higher risk of postoperative metastasis following GTR alone, STR with radiation, STR alone, then GTR with radiation (p < 0.005). Postoperative recurrence was the highest following GTR alone, STR alone, STR with radiation, then GTR with radiation (p < 0.005). Death was seen in patients who underwent GTR alone, STR with radiation, GTR with radiation, and then STR alone(p < 0.005). Patients treated for nerve root melanotic schwannomas had a higher rate of metastasis and death following surgery but a lower rate of recurrence than those treated for intradural melanotic schwannomas.

Conclusion : Outcomes of patients with schwannomas vary based on patient demographics, tumor characteristics, symptoms, and surgical treatment. Among the range of symptoms experienced by these patients, the most common is pain. Patients treated with GTR and radiation had the lowest rate of postoperative metastasis and recurrence, while those treated with STR alone were found to have the highest postoperative survival. Patients treated for nerve root melanotic schwannomas had a higher postoperative metastasis and death but a lower recurrence rate than those treated for intradural melanotic schwannomas.