Oral Melanoma

 Represent < 0.5% of all oral malignancies



• Mean in 6th-7th decades

• M > F (2.5-3:1)

• Hard palate and maxillary alveolus are most common sites of involvement (~ 80%)

• Cervical lymph node metastases reported in > 50% of cases at presentation

• Asymmetric, painless, pigmented lesion with irregular borders

• Radical surgical excision

• Overall, poor prognosis (median: 2 years)




Imaging




• Oral cavity mass with high T1 signal on MR


Microscopic




• In situ component with pagetoid spread of single or multiple melanoma cells in superficial epithelium
• Epithelioid or spindle-shaped morphology of melanocytes containing fine melanin granules

image 15% of oral melanomas have little to no melanin

• 1/3 of cases have bone/cartilage invasion


Ancillary Tests




• Positive:  S100, SOX10, HMB-45; tyrosinase, melan-A, MITF


Top Differential Diagnoses




• Spindle cell squamous cell carcinoma, metastatic melanoma, pleomorphic sarcoma

image
Palatal MM With Satellite Lesions
Primary mucosal melanoma (MM) of the hard palate presents as a diffuse, patchy area of heavy pigmentation with irregular borders image. Satellite lesions are noted away from the main area of pigmentation image.


image
Epithelioid Melanocytes in Nodular MM
Nodular melanoma of the hard palate shows epithelioid malignant melanocytes, some with melanin pigment, expanded into the lamina propria. Individual melanocytes image are seen in the upper layers of the mucosa (pagetoid spread).

image
Pseudoepitheliomatous Hyperplasia in MM
There is a concurrent pseudoepitheliomatous hyperplasia image present in association with an atypical melanocytic proliferation. An inflammatory infiltrate is also present. The melanoma may be obscured or missed due to this process.

image
HMB-45 Highlights Melanocytes in MM
HMB-45 immunohistochemistry highlights the melanocytes present both in the basal layer as well as in the submucosa. This is one of the more specific markers for melanoma. It is important to know that staining can be patchy or focal.


TERMINOLOGY


Definitions




• Malignant neural crest-derived neoplasm with melanocytic differentiation in oral cavity
image Atypical melanocytes at epithelial-connective tissue interface with upward migration or connective tissue invasion


ETIOLOGY/PATHOGENESIS


Etiology




• Unknown: Not related to preexisting mucosal nevi or physiologic pigmentation
• Increased frequency of KIT (c-KIT, CD117) mutations in mucosal melanomas have been reported

image Mutation not often detected in cutaneous melanomas

• BRAF mutations not detected in mucosal melanoma, but seen in cutaneous melanomas


CLINICAL ISSUES


Epidemiology




• Incidence
image Extremely rare, accounting for < 1% of all melanomas

– 0.02/100,000 population/year in USA

image Represent ~ 40% of all head and neck mucosal melanomas

image Represent < 0.5% of all oral malignancies

image Unlike cutaneous melanoma, oral melanoma incidence has been stable

• Age
image Mean: 6th-7th decades; rare in pediatric patients

• Sex
image M > F (2.5-3:1)

• Ethnicity
image More common in Japan and western Africa


Site




• Hard palate and maxillary alveolus are most common sites of involvement (~ 80%)
• Remaining 20% include

image Mandibular gingivae

image Buccal mucosa

image Floor of mouth and tongue


Presentation




• Most arise de novo, although 1/3 are preceded by pigmented lesion for few months or years
image Melanosis reported before development of melanoma

• Asymmetric, painless, pigmented lesion
image Irregular borders or outlines

image Black, purple, red, gray
– 15% of oral melanomas are amelanotic

image Macular, with nodular areas

• Many patients present at advanced stage with pain, ulceration, loose teeth

Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Oral Melanoma
Premium Wordpress Themes by UFO Themes
%d bloggers like this: