BLACK MEDIASTINUM: PRIMARY MEDIASTINAL MELANOMA

Abstract

SESSION TITLE: Case Report Semifinalists 11 SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/21/2019 02:30 PM - 03:15 PM INTRODUCTION: Mediastinal involvement in melanoma commonly occurs as metastatic disease. Rarely, melanoma may occur as a primary tumor in the mediastinum. We present an unusual case of an 80 year old man presenting with a large sub carinal mass infiltrating the airways and esophagus. An endobronchial biopsy of the lymph node was consistent with melanoma. CASE PRESENTATION: An 80 year old caucasian male was evaluated for productive cough with scant hemoptysis and dysphagia of 3 weeks duration. He was an ex-smoker with 70 pack years of smoking in the past. His past medical history was remarkable for hypertension and atrial fibrillation. He denied any subjective fevers, night sweats, decreased appetite or recent changes in weight. General physical exam was positive for an irregularly irregular pulse with stable vitals. A CT scan of the thorax revealed a large subcarinal mass measuring 5.6 x 8.3 x 10 cm (Figure 1). It was invading the left main stem bronchus and encasing the esophagus. The patient underwent a fiberoptic bronchoscopy and the mass was biopsied. The histopathology results were consistent with melanoma (Figure 2). A retrospective skin examination did not reveal any skin or mucosal lesions. We adopted a non surgical approach for treatment as the tumor was infiltrating the airways and esophagus. Palliative radiation was initiated to reduce the tumour burden. An endobronchial stent was placed in the left main stem bronchus to ensure patency and provide symptomatic relief. An esophageal stent was also placed. The patient opted for hospice and passed away peacefully shortly after discharge from the hospital. DISCUSSION: A mediastinal mass in a patient with significant smoking history suggests lung carcinoma. However, in this unusual case, it's biopsy revealed a melanoma. Mediastinal involvement in melanoma commonly occurs as metastatic disease. Since we did not find any skin or mucosal lesions, the lesion was diagnosed to be a primary mediastinal melanoma. In our case, bronchial epithelial tissue containing melanocytes could have given rise to melanoma(1). Alternatively, mediastinal lymph nodes with ectopic melanocytes can progress to melanoma(2). As primary mediastinal melanoma is an uncommon condition, treatment guidelines are not available. Surgical resection, if feasible, offers the best chance of survival. Non surgical options for treatment include systemic chemotherapy, radiotherapy, immunotherapy and targeted therapy(3). CONCLUSIONS: Primary mediastinal melanoma is an unusual occurrence. Since, there are no clinical cues to suspect this condition, an endobronchial biopsy is essential to establish the diagnosis. A thorough retrospective skin examination should be performed to rule out secondary mediastinal involvement. As this is an uncommon condition, there are no guidelines for treatment. Treatment options should be offered on a case-by-case basis. Reference #1: McNab P, Quigley B, Mendoza T, Hakam A, Khalil F, Fishman M, et al. The histogenic origin of melanoma arising in respiratory epithelium of a teratomatous germ cell tumor of the mediastinum: an enigma unraveled from an unlikely source. International journal of clinical and experimental pathology 2012;5(9):982. Reference #2: Krausz T, Azzopardi JG, Pearse E. Malignant melanoma of the sympathetic chain: with a consideration of pigmented nerve sheath tumours. Histopathology 1984;8(5):881-894. Reference #3: Li Z, Jia H, Zhang B, Zhang Y, Li H, Song P. The clinical features, treatment, and prognosis of primary mediastinal malignant melanoma: A case report. Medicine (Baltimore) 2017 Apr;96(17):e6436. DISCLOSURES: No relevant relationships by Puneet Dhillon, source=Web Response No relevant relationships by Harshwant Grover, source=Web Response No relevant relationships by Rehan Saeed, source=Web Response No relevant relationships by Umer Shoukat, source=Web Response No relevant relationships by Nishanth Thalambedu, source=Web Response