Amelanotic Malignant Mucosal Melanoma of the Nasal Cavity: Case Report and Literature Review

Sinonasal malignant melanoma is a rare but aggressive tumor of the head and neck area. It has a poor prognosis. Common symptoms are nasal obstruction, epistaxis, or purulent rhinorrhea. Diagnosis relies on histopathology with immunohistochemistry (IHC) studies. Surgery is the essential treatment, most often supplemented by radiotherapy or immunotherapy. A 63-year-old female patient, with a history of right dacryocystorhinostomy and Parkinson's disease, consulted for symptoms of right nasal obstruction with increasing intensity accompanied by two episodes of mild unilateral epistaxis. Rigid optic examination showed a white-pinkish right obstructive supra-centimetric endonasal tumor. CT revealed an extensive tissue process of the right nasal cavity invading the maxillary sinus, the inferior and middle conchas. A biopsy of the lesion was conducted under local anesthesia. The immunohistochemical study has shown undifferentiated tumor with positive antibody anti PS100 and anti-melan A evoking malignant sinonasal melanoma. The patient underwent two surgeries for maxillectomies as she presented a first local recurrence. She was started on adjuvant radiotherapy. At one year of follow-up, she does not present any local or general signs of disease. Sinonasal melanoma is a particular entity of head and neck mucosal melanomas. The highest incidence is described to be in the seventh and eighth decades of life with no sex difference. IHC profiling of different melanoma subtypes showed the importance of alterations in the KIT gene, this genetic data may constitute a therapeutic target. After surgery, the important local recurrence rates and regional failure justify adjuvant radiotherapy also for resections in free margins. Most authors consider that prophylactic neck dissection is not necessary. Preoperative imaging features (CT scan) are characteristic and helpful for diagnosis. IHC is essential, has a high sensitivity for differentiating achromic melanomas from other neoplasms. Sinonasal achromic melanoma is a very uncommon tumor, invasive, and frequently associated with distant metastasis. Paraclinic examinations are essential for staging and guiding therapeutic management. Immunotherapy is a promising ground of research as it comes to metastatic and advanced disease.