Abstract: Objective To investigate the biological features and histogenesis of pulmonary benign metastasizing leiomyoma (PBML), and to reveal the realationship between PBML and fibromyoma uteri. MethodsThe clinicopathological features and immunohistochemistry of 3 patients with PBML and 3 cases of pulmonary fibroleiomyomatous hamartoma(PFH) were reviewed and compared, respectively. Followed-up data were also obtained. Results The 3 female patients in PBML group had fibromyoma uteri history with average time of 10.6 year from hysterectomia to the appearance of PBML lesions. Chest CT scan showed that multiple well defined nodules in the both lobes of the lungs. The tumors two groups exhibited similar in histopathological and immunohistochemistric features. The optical observation showed that the tumor cells were in fusiform shape, and in scattered layout. The well differentiated adenoid columnar epithelium were observed in the tumors.Immunohistochemistry showed the fusiform shaped cells expressed vimentin, desmin,α-actin, estrogen receptor and progesterone receptor，while didn't express cytokeratin expression, epithelial membrane antigen, S-100, neurospecific enolase and chromogranin A Meanwhile the surfactant proteins adenoid structures also expressed thyroid transcription factor-1, surfactant proteins A, surfactant proteins B and pancytokeratin. There was not significant difference in the expression of these markers in both tumors(P>0.05). The lesions of PBML developed slowly during the 6 months to 4 years follow up. Conclusion The PBML resembled PFH showed the similar histopathological features and immunophenotypes. Fusiform-shaped cells of PBML were similar to the well developed smooth muscle cells and myofibroblasts. Adenoid structures originated from respiratory epithelium. The results suggested that the tumor maybe originate from lung multiple fibroleiomyomatous hamartoma.