Mucosal Melanoma of the Head & Neck

• Mucosal melanomas are rare (<1% of all melanomas), but are very aggressive and have features that are distinct from cutaneous melanoma
• Around 55% of all mucosal melanomas arise within the head and neck region.
  • 2/3 of these arise within the nasal cavity or paranasal sinuses
  • 1/4 arise within the oral cavity
  • The remainder occur sporadically in other sites within the head and neck.
• Historically, the Ballantyne staging system (1970) was used to classify mucosal melanoma across all sites including outside of the head and neck.
  • The Ballantyne staging system simply classified tumours as Stage I (confined to the primary site), Stage II (regional lymph node involvement), or Stage III (distal metastasis).
• Mucosal melanomas involving the nasal cavity or paranasal sinuses were also previously staged with the AJCC system for nasal cavity and paranasal sinus carcinoma.
  • However, evidence suggested that this did not discriminate prognosis between stages with mucosal melanoma well.
  • This also did not provide a staging system for MMs of the other potential disease sites in the head and neck.
• This prompted the creation of a separate staging system for mucosal melanoma involving the head and neck, which was introduced in the AJCC 7^th Edition, and remains unchanged in the 8^th Edition.
• Review of results with this new staging system showed good prognostic discrimination between stages and more recent studies (Luna-Ortiz et al) show superior prognostication versus the Ballantyne staging system.

Survival probability over time by stage (AJCC 7^th Edition)

• Unchanged in the AJCC 8^th Edition versus the 7^th Edition.
• However the AJCC 8^th Edition was later revised to exclude the dry vermillion lip and oral commissure from this staging system.
  • In the initial version, the dry lip (ie. the vermillion) and oral commissure were considered both mucosal and part of the oral cavity.
  • Melanomas involving the dry lip were staged as mucosal melanomas.
  • Other carcinomas involving the dry lip were staged as oral cavity carcinomas.
• In the updated AJCC 8^th Edition, the dry vermillion lip and oral commissure are no longer considered a mucosal surface and is now grouped with the cutaneous skin.
  • As a result, dry lip melanoma is now staged as a cutaneous melanoma, and other dry lip carcinomas are now staged as cutaneous carcinomas of the head and neck.

General Rules

• There is no T1 or T2 category for mucosal melanoma; all primary tumours are classified as at least T3 due to the aggressive nature of the disease.
• Primary tumours limited to the mucosa and underlying soft tissue are considered T3.
• Locally advanced mucosal melanomas are classified as T4a and T4b.
• Mucosal melanoma in situ is very rare and is excluded from this staging system.

General Rules

• Only T3, N0 is classified as Stage III
• All T4b tumours are upstaged to Stage IVB (easy to remember).
• The presence of distant metastasis upstages to Stage IVC
• Stage IVA is used to classify T3/T4a tumours with regional LN metastasis, as well as T4a tumours without regional LN metastasis.