Primary pulmonary melanoma: a report of two cases.

Mototsugu Watanabe,Hiromasa Yamamoto,Junichi Soh,Shinichiro Miyoshi,Shinichi Toyooka,Shinsuke Hashida,Seiichiro Sugimoto

doi:10.1186/s12957-015-0695-2

Mototsugu Watanabe, Hiromasa Yamamoto + Show 5 more

Open Access

https://doi.org/10.1186/s12957-015-0695-2

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Abstract

Malignant melanoma is a refractory malignancy with a dismal prognosis. It generally arises from the skin in most cases, and cases of primary pulmonary malignant melanoma are rare and often behave aggressively. We have treated two cases of localized primary pulmonary malignant melanoma using surgical resection. Pulmonary malignant melanomas often metastasize to the brain and liver; one of our cases exhibited metastasis to the cecum at about 8 months after surgery. Because cutaneous melanomas often carry activating mutations in the BRAF gene (V600E), we performed a BRAF mutational analysis using direct sequencing for both of these tumors arising from the lung. However, no BRAF mutations were detected. We detected a p53 mutation, which was thought to be a potential somatic mutation, in one of the two cases using a sequencing panel targeting 20 lung cancer-related genes. Although we also checked the expression of programmed death ligand 1 (PD-L1) on the surface of the tumor cells by immunohistochemical testing, neither of our two cases expressed PD-L1. Further molecular analyses may uncover the characteristics of primary pulmonary malignant melanomas.

Highlights

Malignant melanoma is an often fatal cutaneous neoplasm
40 to 60 % of cutaneous melanomas carry mutations in the BRAF gene (V600E), which leads to the constitutive activation of downstream signaling through the MAPK pathway [3, 4]
Immunotherapy to inhibit programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) pathway that has a role for immune escape

Summary

Background

Malignant melanoma is an often fatal cutaneous neoplasm. As a primary tumor, malignant melanoma of the lung is rare, accounting for only 0.01 % of all primary lung tumors [1]. To diagnose malignant melanoma as a primary tumor arising from the lung, the absence of primary melanoma lesions at cutaneous or nonpulmonary extracutaneous sites must be demonstrated [2]. Whether pulmonary malignant melanomas carry BRAF mutations has not been reported. Immunohistochemical analysis showed positive cytoplasmic staining of the tumor cells for HMB-45, Tyrosinase, and MART1, the expression of TTF-1 in tumor cells was negative. A CT and PET-CT scan showed a tumor in the left lower lobe of the lung (Fig. 2a, b). Pathological examination of a specimen obtained during a transbronchial lung biopsy revealed that the tumor was a malignant melanoma (Fig. 2c). Because further examinations did not reveal any other tumors that could have been the primary lesion, we diagnosed the lung tumor as a primary pulmonary malignant melanoma. According to the definition of PD-L1 positivity by them, neither of our two cases was considered to express PD-L1 (Figs. 1d and 2d)

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Discussion

Conclusions