Pulmonary papillary adenoma with malignant transformation: report of one case and review of the literature.

: Pulmonary papillary adenoma is a rare tumor. A total of 32 cases was studied, include 31 cases in the literature. Most of the patients were asymptomatic, and tumor was usually discovered during a routine chest roentgenogram or with other disease. Most cases demonstrated benign behavior and there have been no recurrent cases after the operation or biopsy with the follow up of 6 to 120 months. However, there was some evidence indicating it can be locally aggressive or potentially malignant. We present the first case report of cancer development in a pulmonary papillary adenoma. In our case, the imaging findings progressed from initial well-defined border, without 18F-FDG accumulation, to one side rough edge after two years of follow up. Postoperative pathology revealed a partly well-defined tumor, without a fibrous capsule, but focally infiltrated the alveoli. Our case had definite areas of papillary adenoma, with focal acinar and micropapillary adenocarcinoma area near the central fibrosis. The papillary adenoma cells were with polarity and low expression of Ki67 and C-myc, without atypia or mitosis. But the adenocarcinoma cells were obviously different from them, with high expression of Ki67 and C-myc, indicating cancer development. MYC activation may play a role in tumorigenesis, and further investigation was needed. There was no EGFR mutation in both of the components.