It is difficult to distinguish a lung cancer from a pulmonary tuberculoma or other benign nodule. It is even more difficult to identify the type of lesion if the mass shows no change in size or demonstrates slow growth. Only a pathological confirmation can possibly reveal the nature of the lesion. A 61-year-old-woman was referred for a solitary pulmonary nodule. The nodule showed no change in size for the first two years and continued to grow slowly. Pathological and immunological analyses were conducted for confirmation of the nodule. The nodule was identified as a well-differentiated primary pulmonary adenocarcinoma. An LULobectomy was performed, and the post surgical stage of the nodule was IIIA (T2N2M0). Even though there are few risk factors, there is still the possibility of a malignancy in cases of non-growing or slow growing solitary pulmonary nodules. Therefore, pathological confirmation is encouraged to obtain a firm diagnosis.