Primary collision neoplasm of malignant melanoma and adenocarcinoma in the lung. A case report.

We report an extremely rare case of a primary collision neoplasm in the lung consisting of malignant melanoma and adenocarcinoma. A malignant melanoma was histologically diagnosed by a transbronchial lung biopsy of the lung nodule in a 61-year-old woman, in whom there was no demonstrable primary malignant melanoma found elsewhere. However, at autopsy the above two components of the pulmonary tumor were both histologically and immunohistochemically confirmed. There was little intermingling of the two tumors. The malignant melanoma was positive for monoclonal antibody specific for melanotic tumor (HMB45) and S-100 protein but was negative for epithelial membrane antigen (EMA), while it was the opposite in the adenocarcinoma. This case is, to our knowledge, the first reported collision tumor of the above two components.