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  Table of Contents    
LETTER TO EDITOR  
Year : 2016  |  Volume : 59  |  Issue : 4  |  Page : 561-563
Primary mediastinal melanoma: A rare presentation


1 Department of Pathology, King Khalid University, Abha, Kingdom of Saudi Arabia
2 Department of Laboratory Medicine, Aseer Central Hospital, Abha, Kingdom of Saudi Arabia

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Date of Web Publication10-Oct-2016
 

How to cite this article:
Fatima S, Haider N, Mirza NI, Valere D'sa BF. Primary mediastinal melanoma: A rare presentation. Indian J Pathol Microbiol 2016;59:561-3

How to cite this URL:
Fatima S, Haider N, Mirza NI, Valere D'sa BF. Primary mediastinal melanoma: A rare presentation. Indian J Pathol Microbiol [serial online] 2016 [cited 2019 Nov 22];59:561-3. Available from: http://www.ijpmonline.org/text.asp?2016/59/4/561/191772


Editor,

Mediastinal tumors are relatively uncommon and are one of the most challenging specimens examined by surgical pathologists as many different types of lesions involve this site. Primary melanoma of mediastinum is extremely rare. We present a case of a young woman who was diagnosed to have mediastinal melanoma. Melanomas which account for 1.5% of all cancers are malignant tumors composed of melanocytes, which are derived from neural crest cells. Among them, cutaneous melanomas can occur de novo or from a pre-existing nevus and most are found in the head and neck area and on the lower extremities, the latter location being particularly common in females. [1] Noncutaneous primary sites of melanocytes include the mucosal epithelium, retinas, and leptomeninges. The presentation of melanoma in mediastinum is a very rare and unusual occurrence.

A 20-year-old woman presented with a history of difficulty in breathing, dysphagia, weight loss, chest discomfort, severe backache of 2-month duration, and progressive weakness in the lower limbs for 1 month. Computed tomography (CT) scan of the chest with contrast done revealed a 9 cm 10 cm 8 cm posterior mediastinal heterogeneously enhancing solid mass encircling the posterior trachea and extending into the lung and D5 vertebra. CT scan of the abdomen and pelvis was normal. Magnetic resonance imaging of the cervical dorsal spine revealed a large posterior mediastinal, right paraspinal soft tissue mass extending from the level of D1 vertebra down to the level of D9 vertebra. The lesion measured 9 cm 10 cm 8 cm in diameter with intraspinal component and destruction of the body of D5 [Figure 1]a. The possibility of a neurogenic tumor was considered. The tumor was resected, and gross examination revealed a dark brown mass partially surrounded by a fibrous capsule measuring 11 cm 10 cm 6.5 cm, with cut sections showing friable black tissue [Figure 1]b. Histopathologic examination revealed malignant pleomorphic cells with abundant eosinophilic to clear cytoplasm, prominent nucleoli, extensive pigment deposition, large areas of necrosis with lymphovascular invasion [Figure 2]a and mitotic count of 8-10/10 HPF. Immunohistochemical stains tested positive for vimentin, human melanoma black (HMB 45) [Figure 2]b, S-100 [Figure 2]c, Ki-67 LI - 12% [Figure 2]d and negative for leukocyte common antigen, epithelial membrane antigen, and cytokeratin, and a diagnosis of malignant melanoma was made. No evidence of primary lesion in skin or elsewhere was found.
Figure 1: (a) Magnetic resonance imaging of the cervical dorsal spine revealing a large posterior mediastinal right paraspinal soft tissue mass with intraspinal component and destruction of the body of D5. (b) Gross examination showing a dark brown - black friable tumor mass partially surrounded by a fibrous capsule

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Figure 2: (a) Malignant pleomorphic cells with eosinophilic to clear cytoplasm, some cells showing pigmentation, prominent nucleoli (H and E, ×40) immunohistochemical study (b) human melanoma black 45 showing positivity for malignant cells (human melanoma black 45 immunostain, ×10), (c) S100 showing nuclear and cytoplasmic positivity for malignant cells. (S100 immunostain, ×40) (d) Ki - 67 (×40)

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Malignant melanomas have been described in nearly every organ besides the skin, but its occurrence in mediastinum is extremely rare. Melanomas are derivatives of neural crest cells which are transient and multipotent and develop into melanocytes, peripheral and enteric neurons, glia, craniofacial cartilage, bone, and smooth muscle. [1] These tumors may arise from nevus cell aggregates in mediastinal nodes and thymus giving rise to anterior mediastinal involvement and from sympathetic chain in posterior mediastinum. [2] In utero migration of melanocytes with the rest of the embryonic respiratory tract from primitive foregut is another plausible pathogenesis for primary melanoma occurring in the mediastinum. [3] A few cases of mediastinal melanoma have been reported in the past. [2],[4] Our patient presented with an involvement of posterior mediastinum which is frequently the site for neurogenic tumors, esophageal tumors, duplication cysts, hiatus hernia, and neurenteric cysts. In adults, neurogenic tumors, thymomas, and thymic cysts are the most frequently encountered lesions in mediastinum. Since both Hodgkin and non-Hodgkin lymphoma and germ cell tumors are most common between the ages of 20 and 40, the likelihood of a mediastinal mass being malignant is increased among patients in this age group. [5] Our case presented with melanotic cells, so the differentials were pigmented extra-adrenal paraganglioma, pigmented carcinoid tumor of thymus, melanotic schwannoma, melanotic neuroectodermal neoplasm, and primary malignant melanoma. Posterior mediastinum is a common location for nerve sheath tumors, so in our case, the closest differential was melanotic schwannoma. These tumors show extensive melanin pigment, HMB 45, and S-100 positivity (cytoplasmic) whereas our case showed nuclear and cytoplasmic positivity for S-100 like melanomas. The mitotic activity and Ki-67 LI were high in our case unlike melanotic schwannomas. The prognosis of primary malignant melanoma in mediastinum is unfavorable, and surgical resection is the best treatment which was done in our case. Systemic chemotherapy and immunotherapy can be used to treat advanced disease. [4]

Primary melanoma of the mediastinum is a very rare and aggressive tumor. It can present as a large mass, making surgical resection difficult due to close vicinity with important structures.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Huang X, Saint-Jeannet JP. Induction of the neural crest and the opportunities of life on the edge. Dev Biol 2004;275:1-11.  Back to cited text no. 1
[PUBMED]    
2.
Vlodavsky E, Ben-Izhak O, Best LA, Kerner H. Primary malignant melanoma of the anterior mediastinum in a child. Am J Surg Pathol 2000;24:747-9.  Back to cited text no. 2
[PUBMED]    
3.
Taboada CF, McMurray JD, Jordan RA, Seybold WD. Primary melanoma of the lung. Chest 1972;62:629-31.  Back to cited text no. 3
[PUBMED]    
4.
Rubush JL, Gardner IR, Boyd WC, Ehrenhaft JL. Mediastinal tumors. Review of 186 cases. J Thorac Cardiovasc Surg 1973;65:216-22.  Back to cited text no. 4
[PUBMED]    
5.
Kim HR, Lee JS, Kim YT, Kim JH, Kim JE. Primary malignant melanoma presenting as an anterior mediastinal mass. Korean J Thorac Cardiovasc Surg 2002;35:697-700.  Back to cited text no. 5
    

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Correspondence Address:
Sohaila Fatima
Department of Pathology, King Khalid University, Abha
Kingdom of Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.191772

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