Figure 1.

Radiographic imaging at diagnosis and pathological findings. (A) The subsolid nodule under the pleura of the upper left lobe and the soft tissue density nodule in the right middle lobe and near the hilum revealed by computed tomography (CT) or positron emission tomography (PET). (B) Pathological examination revealed the subsolid nodule under the pleura of the upper left lobe was adenocarcinoma. Pathology showed the initial and the second biopsy of soft tissue density nodule in the right lung were adenosquamous carcinoma and squamous carcinoma, respectively. Interpretation of immunohistochemistry (IHC) performed on the initial biopsy was challenging as most tumor cells were TTF-1 positive suggesting adenocarcinoma. However, there was clear and diffuse positivity for p40 in some cells with corresponding lack of Napsin A. This suggested both glandular and squamous differentiation. In the second biopsy, p40 was diffuse with complete lack of adenocarcinoma markers TTF-1 and Napsin A, consistent with squamous cell carcinoma.