A Case of Metastatic Endobronchial Melanoma from an Unknown Primary Site

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169 http://dx.doi.org/10.4046/trd.2012.72.2.169 ISSN: 1738-3536(Print)/2005-6184(Online) Tuberc Respir Dis 2012;72:169-172

CopyrightⒸ2012. The Korean Academy of Tuberculosis and Respiratory Diseases. All rights reserved.

A Case of Metastatic Endobronchial Melanoma from an Unknown Primary Site

Jaehee Lee, M.D.

¹

, Shin Yup Lee, M.D.

¹

, Seung Ick Cha, M.D.

¹

, Byeong-Cheol Ahn, M.D.

²

, Jae Yong Park, M.D.

¹

, Tae Hoon Jung, M.D.

¹

, Chang Ho Kim, M.D.

¹

Departments of

¹

Internal Medicine, and

²

Nuclear Medicine, Kyungpook National University School of Medicine, Daegu, Korea Melanoma can occur as a metastasis within subcutaneous tissue, lymph nodes, or viscera without a detectable primary tumor. Among patients with metastatic melanoma of unknown primary lesion, those with endobronchial metastasis are exceedingly rare. Herein we report a case of an endobronchial and pulmonary metastasis in a patient with melanoma originating from an unknown primary site. The patient without a previous history of melanoma presented with blood-tinged sputum. Fiberoptic bronchoscopy revealed a black polypoid tumor obstructing the posterior basal segmental bronchus of the right lower lobe. A final diagnosis of the malignant melanoma was made based on an immunohistochemical study of the bronchoscopic biopsy specimen. Skin, ophthalmic, oral, and nasal examinations failed to identify occult primary lesions. Subsequent evaluation including positron emission tomography/computed tomography scans did not uncover any abnormalities other than the metastatic pulmonary melanoma. We also describe the characteristic bronchoscopic features of melanoma.

Key Words: Melanoma; Neoplasm Metastasis; Bronchi

Address for correspondence: Chang Ho Kim, M.D.

Department of Internal Medicine, Kyungpook National University Hospital, 50, Samdeok-dong 2-ga, Jung-gu, Daegu 700-721, Korea

Phone: 82-53-420-5537, Fax: 82-53-426-2046 E-mail: [email protected]

Received: Jun. 22, 2011 Revised: Jun. 27, 2011 Accepted: Aug. 22, 2011

Introduction

Malignant melanoma of unknown primary site (MUP) is defined as histologically-confirmed subcutaneous, no- dal, or visceral metastatic melanoma occurring without any known cutaneous, mucosal, or ocular primary le- sion

¹

. A recent comprehensive systemic review of the existing literature

²

showed that the incidence of MUP is estimated to be 3.2% although this figure varies con- siderably between different studies

^3,4

. Amongst patients who are diagnosed with MUP, those with visceral meta- stasis are relatively infrequent compared to ones with subcutaneous or lymphnode metastasis

^2-5

. Even in- dividuals with endobronchial metastasis from unknown

primary melanoma are extremely sparse

⁶

. Herein we re- port a case of MUP with endobronchial metastasis showing characteristic bronchoscopic features.

Case Report

A 74-year-old man presented with one-month history of coughing and blood-tinged sputum. He was a former smoker who smoked half a pack of cigarettes per day between the ages of 20 and 69 years. He had also worked as a coal miner for past 14 years and had been diagnosed with coal worker’s pneumoconiosis 5 years ago. He had no history of previous skin excisions or resected ocular tumors.

Physical examination revealed a fixed localized wheezing in the right lower lung zone. Routine labo- ratory studies and blood chemistries were normal. Chest x-rays showed numerous small nodules in the bilateral whole lungs (Figure 1A). These bilaterally-scattered nodules did not appear to have significantly changed compared to his past chest x-ray. However, a mass measuring 2.2×3.4 cm in the right lower lobe and sev-

Case Report

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J Lee et al: Occult primary melanoma in bronchus

170 Figure 1. (A) Chest radiograph. Numerous small nodules were evenly scattered throughout both lungs with increased opacities toward the bilateral lower lobes. (B) Chest CT. Enhanced chest CT scan displayed a mass measuring 2×3 cm in the right lower lobe (white arrow) and another small nodule in the left lower lobe (gray arrow). (C) Bronchoscopic finding. A black polypoid tumor was found to be obstructing the posterior basal segmental bronchus of the right lower lobe. CT: computed tomography.

Figure 2. Histologic findings. Tumor cells with a prominent nucleus and brown pigment in the cytoplasm are shown (A, H&E stain, ×400). Immunohistochemical staining for S100 (B) and HMB45 (C) was positive.

eral nodules of various size (range, 0.8∼1.6 cm) in both lungs along with pneumoconiotic nodules were observed on computed tomography (CT) scans of the chest (Figure 1B). The patient then underwent a bronchoscopy. A black polypoid tumor obstructing the posterior basal segmental bronchus of the right lower lobe was found (Figure 1C).

Histologic examination of the bronchoscopic biopsy specimen showed that the lesion was composed of large round and spindle-shaped cells arranged in closely packed sheets (Figure 2). Large amounts of fine gran- ular pigment were present within the tumor cells.

Immunohistochemical staining showed that the tumor cells were positive for S-100 and HMB-45. Therefore, the patient was diagnosed with malignant melanoma.

F-18 fluorodeoxyglucose (FDG) positron emission to- mography (PET)/CT scan was performed, which showed a metabolically active lesion in the right lower lobe (maximum standardized uptake value [SUVmax], 6.3; Figure 3). Additionally, several nodules seen in both lungs by CT were metabolically active (SUVmax, 7.0). However, cutaneous, mucosal, or ocular lesions suggesting primary melanoma were not detected.

Subsequent evaluation including brain magnetic reso- nance imaging, esophagogastroduodenoscopy, and co- lonoscopy did not uncover any additional abnormalities.

Skin, ophthalmic, oral, and nasal examinations by spe- cialists failed to identify any occult primary lesions.

Interferon-α therapy was recommended, but the pa-

tient refused treatment. Follow-up CT scan of chest was

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Tuberculosis and Respiratory Diseases Vol. 72. No. 2, Feb. 2012

171 Figure 3. F-18 fluorodeoxyglucose PET/CT scan. PET/CT scan revealed a metabolically active mass (arrow) with a max- imum standardized uptake value of 6.3 in the right lower lobe. (A) Transaxial fusion PET/CT image. (B) Transaxial PET image. PET: positron emission tomography; CT: computed tomography.

performed 3 months after discharge when he presented with worsening dyspnea at emergency department. It showed increases in the size of previous endobronchial and several pulmonary lesions found metabolically ac- tive in PET/CT scan. Ultimately, he died of respiratory failure due to tumor progression 4 months after his ini- tial diagnosis.

Discussion

Most primary melanomas develop as cutaneous le- sions, and a few develop in recognized mucosal or ocu- lar sites. MUP is the term used to describe a relatively uncommon situation in which patients have metastatic melanoma, but no known primary cutaneous, mucosal or ocular lesions. This unusual condition was initially characterized by Dasgupta et al.

¹

who first described the criteria for MUP in 1963. Careful examination is essen- tial when searching for primary tumors and includes the following: a complete exam of the skin and mucosal surfaces, ophthalmologic and otolaryngologic examina- tions, gastrointestinal endoscopic examination, and cer- ebral, neck, thoracic, and abdominal CT scan

⁷

. In the present study, PET/CT scans in addition to a thorough evaluation that included the procedures mentioned above were performed to identify a potential primary site. Although the use of PET/CT for evaluating the pri- mary site of MUP is not well established

⁸

, this technique

might be helpful for detecting a primary site in patients with MUP. This possibility is supported by the fact that the incidence of MUP has been reduced since the in- troduction of CT scan

²

.

To date, the etiology of MUP remains unclear al-

though various hypotheses have been developed

^1,3

. The

first proposal is that MUP results from complete sponta-

neous regression of the primary melanoma

³

. Partial or

complete spontaneous resolution of melanoma cells

from the primary site is fairly common and it was ac-

tually described in various study

²

. A second assumption

is that the melanoma originates from melanocytes in

lymph nodes or viscera

^1,4

. In fact, malignant melanoma

detected in the lung may represent a primary lesion that

has arisen in the lung. However, diagnosing primary

pulmonary melanoma requires strict criteria which pro-

duce evidence that suggests a primary occurrence in the

lung

^9-11

. One of the criteria is that the pulmonary lesion

should be solitary. Our patient with an endobronchial

tumor and multiple pulmonary nodules did not fulfill

it. Moreover, his pathologic features did not show junc-

tional change with invasion of intact bronchial mucosa

by malignant melanoma cells suggested as histopatho-

logical criteria for primary pulmonary melanoma

⁹

.

Therefore, he was finally diagnosed with MUP when

considering these currently proposed criteria for primary

pulmonary melanoma. However, pathologic examina-

tion was performed in not a surgically removed speci-

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J Lee et al: Occult primary melanoma in bronchus

172 men but the bronchoscopically obtained smaller one. It would limit accurate pathologic assessment for differ- entiating between primary and metastatic pulmonary melanoma. Therefore, the possibility that our patient might have a primary pulmonary melanoma with lung to lung metastasis cannot be completely excluded.

Endobronchial metastases of malignant melanoma de- tected bronchoscopically are also uncommon

^12,13

. The tumor in the present case had a black polypoid appearance. This differed from previous cases that had yellowish or brown nodular lesions

^6,14,15

. If a broncho- scopist encounters an endobronchial mass with the characteristics similar to the ones described in our study, malignant melanoma should be considered as an initial exclusive diagnosis.

Interestingly, the patient in the present case had worked as a coal miner. Consequently, he was diag- nosed with coal worker’s pneumoconiosis 5 years prior to this study. We could not find any existing literature on the relationship between malignant melanoma and coal worker’s pneumoconiosis.

In general, the management of MUP patients is the same as that of stage-matched melanoma cases with a known primary site

²

. The role of adjuvant systemic che- motherapy remains unclear. As presented by the short survival time of our case, the prognosis for patients with visceral cases of MUP is generally poor

²

.

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