Introduction
Primary oral mucosal melanoma (OMM) is a very uncommon entity that makes up about 1-8% of all malignant melanoma and less than 0.5% of all oral malignant tumors.1.2OMM arises from oral melanocyte which seems to be part of the oral immune system.1.3
Maxillary gingiva and hard palate are the most common sites of primary OMM. The tongue specifically is an infrequent site and represents less than 2% of all oro-nasal melanoma cases. 4 To the best of our knowledge regarding English literature review, about 30 cases of primary malignant melanoma of the tongue were reported.
OMM has different etiohistopathology, genetic mutation, and prognosis compared to cutaneous malignant melanoma. The exact etiology of OMM is still unknown. Although alcohol consumption, tobacco use, cigarette smoking, and denture trauma are reported to affect the occurrence of OMM.5.6 Most of them are thought to be De Novo. Oral pigmentation precedes the development of malignant melanoma in about one-third of the patients.4.7 However, the mechanism of this transformation is not clearly understood yet.8.9
Oral melanoma can manifest as a macule, plaque, or mass. Therefore, they are very easy to diagnose clinically because of their appearance in contrary to nasal mucosal melanoma which cannot detect or diagnose easily due to their location. However, they are often asymptomatic and connived or misdiagnosed as benign pigmented lesions until advanced stages when they become ulcerative or hemorrhagic, or painful.  Delayed diagnosis can be one of the reasons for the poor prognosis of OMM.
Early detection and treatment would improve the prognosis significantly.10 The treatment modality of choice is not well depicted due to its rarity and poor prognosis. Radical surgery currently is the “gold standard” and main treatment of OMM. It can be combined with neck dissection, depending on cervical lymph node status. Non-surgical treatment options, like radiotherapy and medical therapy (e.g., checkpoint inhibitors), can be used as adjuvant treatment depending on stage.1 The size and depth of the tumor, lymphovascular invasion(LVI), necrosis, polymorphic neoplastic cells, lymph node involvement, and metastasis straightly affect the prognosis.11 The five-year survival rate of OMM is about 15–38% which is the lowest among other melanoma.3
Melanomas of the oral cavity and tongue are commonly found in patients older than 40 years, and males are affected slightly more than females.10
The early asymptomatic phase and difficulty in gaining complete radical excision with safe margins are two important factors that contribute to a bad prognosis. Hence, consideration of malignant melanoma in the differential diagnosis of pigmented as well as non-pigmented lesions of tongue and oral mucosa is critical, regardless of the age of the individual. The thorough clinical examination followed by histopathological and immunohistochemical study in suspicious lesions is imperative to rule out oral melanoma.
We present a rare report of a young woman with a recurrence of tongue melanoma while on maintenance treatment with imatinibR, who was treated by partial glossectomy with submental flap reconstruction and adjuvant radiotherapy.