A Case of Primary Pleural Melanoma

Abstract

SESSION TITLE: Rare Thoracic Neoplasms SESSION TYPE: Global Case Report Poster PRESENTED ON: Tuesday, October 31, 2017 at 01:30 PM - 02:30 PM INTRODUCTION: This case report describes a rare presentation of melanoma and emphasizes the importance of the cytological and immunocytochemical analyses of pleural fluid. CASE PRESENTATION: An 83-year-old Japanese male presented with left-sided chest pain and dyspnea lasting a few hours. He had a history of old myocardial infarction and paroxysmal atrial fibrillation. He drank alcoholic beverages occasionally and was non-smoker. Initial vital signs were unremarkable. There was no lymphadenopathy or hepatosplenomegaly. Breath sounds were decreased and dullness was present at the base of the left lung. Cardiovascular examination was normal. Laboratory test values were as follows: white blood count cell, 4770/mm3; hemoglobin, 14.8 g/dL; platelet count, 84,000/mm3; random serum glucose, 147 mg/dl; serum lactate dehydrogenase, 387 U/l; serum albumin, 3.3 g/dl; serum C-reactive protein, 0.34 mg/dl. Chest radiograph showed a large amount of pleural effusion in the left hemi-thorax, and the chest computed tomography scan showed multiple nodular soft tissue thickenings of the left hemi-pleura and mediastinum with pleural effusion. Thoracentesis was performed and macroscopically the pleural effusion was bloody. The cytological examination of the plural fluid revealed mono or multinucleate large malignant cells in loose aggregates. There were large eccentric nuclei with prominent nucleoli and granular cytoplasmic melanin pigment. On the immunehistochemical examination, the malignant cells were positive for the expression of human melanoma black-45 and S-100, and negative for calretinin, D2-40, desmin, EMA, TTF-1 and Napsin A, which further supported the diagnosis of melanoma. An ultrasonography-guided transthoracic biopsy of the nodular soft tissue thickening of the left hemi-pleura was performed, and the histological/immunohistochemical examinations confirmed the diagnosis. Detailed physical examinations of the patient failed to reveal any site for the primary melanoma in the skin, eyes, oral cavity, genital or anal regions.The patient received chemical pleurodesis using OK-432 for the relief of dyspnea due to the malignant plural effusion, and thereafter, he declined any further treatment. He died of respiratory failure 1 month after the diagnosis. The autopsy disclosed muddy black-colored tumor widely disseminated in the left thoracic cavity. The tumor mainly located in the left visceral pleura and invaded into the left lung tissue. Moreover, the tumor also disseminated to the left parietal pleura, diaphragm, peritoneum and mesenterium. No primary site was found anywhere, including skin and other mucous membranes. From these findings, this patient can be designated as primary pleural melanoma. DISCUSSION: Melanoma predominantly arises in the skin or mucosa close to the skin, and primary pleural melanoma is extremely rare. To our best knowledge, only four cases have been reported in the English literature. Not for pleural but for primary pulmonary melanoma, Jensen and Egedorf proposed the following six clinical criteria for diagnosis: (1) no previously removed pigmented skin tumors, (2) no ocular tumors removed, (3) a solitary tumor in the surgical specimen, (4) tumor morphology compatible with a primary tumor, (5) no demonstrable melanoma in other organs at time of operation, and (6) autopsy without primary melanomas being demonstrated elsewhere. These criteria should be also applied well to primary pulmonary melanoma, and our patient satisfied all of them. It has been considered that melanoblasts arise from the neural crest and migrate to all parts of the body. Moreover, it is also considered that cutaneous nerve cells can enter dermal lymphatic vessels and travel through the lymphatic system. These mechanisms may explain the pathogenesis of primary pleural melanoma. CONCLUSIONS: In conclusion, our patient can be diagnosed as primary pleural melanoma which is extremely rare condition. This case highlights the importance of cytomorphologic and immunocytochemical analyses in the differential diagnosis of pleural effusion. Reference #1: Nigogosyan G, de la Pava S, Pickren JW. Melanoblasts in vaginal mucosa. Origin for primary malignant melanoma. Cancer 1964;17: 912-913. Reference #2: Biddle DA, Evans H, Kemp BL, et al. Intraparenchymal nevus cell aggregates in lymph nodes: A possible diagnostic pitfall with malignant melanoma and carcinoma. Am J Surg Pathol 2003;27: 673-681. Reference #3: Jensen OA, Egedorf J. Primary malignant melanoma of the lung. Scand J Respir Dis. 1967;48:127-35. DISCLOSURE: The following authors have nothing to disclose: Kojin Murakami, Kazunori Tobino No Product/Research Disclosure Information