Ann Thorac Surg 1999;67:851-852
© 1999 The Society of Thoracic Surgeons
Case Reports
Malignant melanoma presenting as a mediastinal mass
Christine L. Lau, MDa,
Rex C. Bentley, MDb,
Jon P. Gockerman, MDc,
Loretta G. Que, MDc,
Thomas A. D’Amico, MDa
a Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA
b Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
c Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA
Accepted for publication September 9, 1998.
Address reprint requests to Dr D’Amico, Department of Surgery, Duke University Medical Center, Box 3496, Durham, NC 27710
e-mail: damic001{at}mc.duke.edu
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Abstract
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A case of malignant melanoma presenting as a mediastinal mass without an extrathoracic primary is reported. Microscopically the tumor appeared consistent with malignant melanoma, with the presence of focal melanin pigment in large epithelioid cells. Fontana stain confirmed the presence of melanin pigment. Immunohistochemical staining further suggested melanoma, with the tumor cells expressing a HMB45+, S100+ and cytokeratin-phenotype. Electron microscopy showed an abundance of melanosomes confirming the diagnosis of malignant melanoma.
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Introduction
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Malignant melanoma presenting in the mediastinum without an extrathoracic primary is extremely rare, with only a few reports in the literature [1, 2]. We describe a unique case of malignant melanoma, confirmed by histopathologic, immunohistochemical, and electron microscopic examinations, presenting as a right paratracheal mass with no evidence of extrathoracic disease.
A 72-year-old white woman was in good health until August 1997 when bilateral shoulder and pleuritic pain developed after lifting wood into her car. She went to her local emergency room for evaluation, where a chest radiograph was done. It showed a large right paratracheal mass (Fig 1). The patient subsequently had a chest, abdomen, and pelvic computed tomographic scan, which confirmed the presence of a right 4.0 x 4.2-cm paratracheal mass (Fig 2) and revealed extensive mediastinal adenopathy containing cystic areas. The rest of the scan was normal. She was referred to Duke University Medical Center where a bronchoscopy performed December 1997 showed no endobronchial lesions. Mediastinoscopy was performed January 1998, and biopsy specimens were taken of the right paratracheal mass. Routine histologic studies showed focal melanin pigment in large epithelioid cells and indicated malignant melanoma consistent ith metastasis in a lymph node. A Fontana stain confirmed the presence of melanin pigment. Immunohistochemical staining further indicated melanoma with the tumor cells expressing a HMB45+, S100+, and cytokeratin-phenotype. Electron microscopy showed an abundance of melanosomes confirming the diagnosis of malignant melanoma (Fig 3).
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Fig 3. Electron micrograph of tumor cell showing abundance of melanosomes at various stages of maturation (arrows). Mitochondria (asterisk) are identified (lead citrate, uranyl stain; x54,250 after 53.7% reduction).
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No evidence of primary melanoma outside the mediastinum was found. The patient had two skin lesions removed in 1993 and 1996. The pathology slides from these lesions were reviewed at Duke and showed a basal cell carcinoma on her right posterior neck in 1993 and a well-differentiated squamous cell carcinoma on her left distal forearm in 1996. As opposed to the mediastinal tumor, these showed no pigmentation or other features of melanocytic differentiation. Physical examination was notable only for vitiligo of the patient’s upper extremities. Results of pelvic examination including PAP smear were normal. Bone scan and brain magnetic resonance imaging showed no evidence of metastatic disease.
The patient has begun chemotherapy per the Dartmouth protocol consisting of dacarbazine, carmustine, cisplatin, and tamoxifen. At the time of this report, she has finished her first cycle and currently is doing well.
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Comment
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Although melanoma usually presents cutaneously, it can occur wherever melanin cells are present. Although visceral melanomas have been reported, there remains debate over the origin of the primary tumor. Baab and McBride [3] reported a series of 2,446 patients with malignant melanoma and found 4% with an unknown primary site. These tumors could be metastatic from primary lesions that have regressed, or they could be de novo melanomas.
Melanoma is seen in the mediastinum, but it is almost always metastatic. Chen and colleagues [4] reported a series of 1,600 patients treated for malignant melanoma at one institution and found that 260 (16.3%) developed thoracic metastasis. In that series the radiographic pattern of mediastinal or hilar adenopathy alone was found in 6.9% of the intrathoracic metastases. In contrast to metastatic mediastinal involvement, there have been only a few case reports of melanoma presenting primarily in the mediastinum. Feldman and Kricun [1] reported a case of melanoma presenting as a mediastinal mass, on the basis of routine histopathology, but the actual diagnosis of this mass was not confirmed by immunohistochemical staining and electron microscopy. In the Japanese literature, Shishido and associates [2] reported a case of primary mediastinal amelanotic melanoma presenting as superior vena cava syndrome confirmed at autopsy. It is unclear whether the patient had a history of skin lesions.
The present patient had upper extremity vitiligo. Duhra and Ilchyshyn [5] described a patient with vitiligo and melanoma presenting as axillary lymphadenopathy without a known primary. No recurrence was seen in their patient after surgical resection of the involved lymph nodes during the 10-year follow-up. Whether the presence of vitiligo in our patient portends a better prognosis is yet to be seen.
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References
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Feldman L., Kricun M. Malignant melanoma presenting as a mediastinal mass. JAMA 1979;241:396-397.[Abstract/Free Full Text]
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Shishido M., Nagao N., Miyamoto K. Mediastinal amelanotic melanoma presenting as superior vena cava syndrome. Nippon Kyobu Shikkan Gakkai Zasshi (Jpn J Thorac Dis) 1997;35:240-244.
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Baab G.H., McBride C. Malignant melanoma: the patient with an unknown site of primary origin. Arch Surg 1975;110:896-900.[Abstract/Free Full Text]
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Chen J., Dahmash N., Ravin C., et al. Metastatic melanoma to the thorax: report of 130 patients. AJR: Am J Roentgenol 1981;137:293-298.[Abstract/Free Full Text]
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Duhra P., Ilchyshyn A. Prolonged survival in metastatic malignant melanoma associated with vitiligo. Clin Exp Dermatol 1991;16:303-305.[Medline]
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Abstract
Introduction
