Sinonasal mucosal melanoma

Dr Henry Knipe et al.

Sinonasal mucosal melanoma (SNMM) is a very rare and unique subtype of malignant melanoma.

SNMMs account for ~1% of malignant melanomas and <4% of head and neck cancers 1,2. They affect older patients (60-90 years old) 2. There is a higher incidence in Japan 5

Headache and visual symptoms are common. 

Typically SNMMs are an expansile mass centred within the nasal cavity (more common) or the paranasal sinuses. Invasion is common, in particular to the orbits, base of the skull, intracranially, or nasopharynx. Hepatic metastases are common 4

Radiographic features of SNMM are variable, especially on MRI, due to varying amounts of melanin, with up to one-third of cases being amelanotic 3

CT
  • polypoid or mass-like
  • bony remodelling +/- erosion commonly present
  • strongly contrast enhancing 5
MRI
Signal characteristics
  • T1: homogeneous T1 signal
    • high T1 signal may be seen secondary to haemorrhage or melanin 5
  • T2: low signal
  • T1C+: moderate homogeneous or heterogeneous enhancement

Metastases return the same signal characteristics as the primary lesion.

SNMM is aggressive and carries a poor prognosis with a five-year survival rate of ~30% 3

As a general differential in the sinonasal region consider other tumours such as:

As a broader differential in the nasopharyngeal region, consider other nasopharyngeal tumours such as:


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Article Information

rID: 33590
Section: Pathology
Synonyms or Alternate Spellings:
  • Primary sinonasal melanomas
  • Sinonasal mucosal melanomas
  • Sinonasal melanomas (SNM)
  • Sinonasal mucosal melanoma (SNMM)
  • Sinonasal mucosal malignant melanoma (MMM)

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Cases and Figures

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    Case 1: T1
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    Case 1: T1 C+ fat sat
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    Case 2
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