Sinonasal mucosal melanoma
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.
- polypoid or mass-like
- bony remodelling +/- erosion commonly present
- strongly contrast enhancing 5
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.
Treatment and prognosis
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:
- inflammatory and infective conditions
- granulomatosis with polyangiitis (Wegener granulomatosis)
- paranasal sinus mucocoele
- silent sinus syndrome
- masses and neoplasms
- fibrous-osseous lesions
- 1. Narasimhan K, Kucuk O, Lin HS et-al. Sinonasal mucosal melanoma: a 13-year experience at a single institution. Skull Base. 2009;19 (04): 255-62. doi:10.1055/s-0028-1115321 - Free text at pubmed - Pubmed citation
- 2. Batra K, Chhabra A, Rampure J et-al. CT and MRI appearances of primary sphenoid melanoma: a rare case. AJNR Am J Neuroradiol. 2006;26 (10): 2642-4. Pubmed citation
- 3. Nguyen B. Sinonasal malignant melanoma with diffuse metastasis: F-18 FDG PET/CT imaging. Radiology Case Reports. 03;3 (1): . doi:10.2484/rcr.v3i1.118
- 4. O'Regan K, Breen M, Ramaiya N et-al. Metastatic mucosal melanoma: imaging patterns of metastasis and recurrence. Cancer Imaging. 2013;13 (4): 626-32. doi:10.1102/1470-7330.2013.0055 - Free text at pubmed - Pubmed citation
- 5. Eggesbø HB. Imaging of sinonasal tumours. Cancer Imaging. 2012;12 (1): 136-52. doi:10.1102/1470-7330.2012.0015 - Free text at pubmed - Pubmed citation