At autopsy, a massively spreading tumor was noted in the right lung with characteristic histopathological feature of small clusters with no fibrovascular cores surrounded by clear spaces, a typical structure of micropapillary component (A, H.E. ×400). This MPC was also noted around the thyroid papillary carcinoma (B, arrows, H.E. ×400). Immunohistochemical analysis revealed that surfactant protein (SP) was positive in MPC (C, arrows) but negative in papillary carcinoma (C, IHC, ×400), indicating that MPC was derived from adenocarcinoma of the lung with MPC.