Atypical adenomatous hyperplasia is considered to be a preliminary lesion for pulmonary adenocarcinoma while lung hamartomas (mesenchymomas) are non-neoplastic, tumor-like malformations. A patient underwent transthoracic fine-needle aspiration biopsy for a pulmonary mass and then lingulectomy following a diagnosis of adenocarcinoma. The surgical specimen was solid and 25 mm in diameter. Microscopic investigation revealed that the mass was a hamartoma with an atypical adenomatous hyperplasia focus at the periphery. We believe that the cells leading the cancer diagnosis had come from the atypical adenomatous hyperplasia focus around the hamartoma. We presented this case as atypical adenomatous hyperplasia contains atypical epithelium and can be diagnosed as a malignancy on fine needle aspiration biopsy and the coexistence of atypical adenomatous hyperplasia and hamartoma has not been reported previously.