Malignant melanotic nerve sheath tumor

Malignant melanotic nerve sheath tumors or melanotic schwannomas or are an uncommon variant of schwannomas with malignant potential.

The age groups of peak incidence are slightly younger than that of conventional schwannomas, occurring most often in the third through fifth decades 1,5.

Melanotic schwannomas occur in two forms depending on the presence or absence of psammoma bodies

  1. non-psammomatous melanotic schwannoma
  2. psammomatous melanotic schwannoma

Non-psammomatous melanotic schwannomas almost invariably affect the spinal nerves and paraspinal sympathetic ganglia 1,2

Psammomatous melanotic schwannoma also arise from spinal nerves and paraspinal ganglia, but may also involve cranial nerves and visceral autonomic nerves 1

Approximately half of individuals diagnosed with these tumors have underlying Carney complex 1-3

Melanotic schwannomas appear as well circumscribed masses of variable pigmentation ranging from grey to black, depending on the amount of melanin 3

Melanotic schwannomas are composed of Schwann cells which contain melanosomes 1,2. Psammomatous tumors also contain psammoma bodies 3.

The appearances of melanotic schwannomas are similar to conventional schwannomas except that they usually have intrinsic high T1 signal and T2 signal loss due to the presence of melanin 4

Complete resection is usually curative 3. Although generally indolent, approximately 10% of melanotic schwannomas are malignant 1,3. Metastatic disease occurs in a significant minority.

Consider lesions with subacute hemorrhage, such as cavernous malformation, that can account for T1 hyperintensity 5 .

Article information

rID: 53324
Synonyms or Alternate Spellings:
  • Melanotic schwannoma
  • Malignant melanotic nerve sheath tumours
  • Psammomatous melanotic schwannoma
  • Non-psammomatous melanotic schwannoma
  • Pigmented schwannoma
  • Melanotic nerve sheath tumour
  • Melanogenic schwannoma

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