%0 Review %T Unexpected Histopathological Diagnosis of Placental Transmogrification of the Lung after Bullectomy for Recurrent Spontaneous Pneumothorax: A Case Report and Literature Review. %A Shiraishi J %A Akamine T %A Kato S %A Miura N %A Kometani T %A Shikada Y %A Hayashi T %J Ann Thorac Cardiovasc Surg %V 28 %N 6 %D Dec 2022 20 %M 33980751 %F 1.889 %R 10.5761/atcs.cr.21-00005 %X We report a 33-year-old man who presented with recurrent right pneumothorax. Computed tomography (CT) showed the presence of a large bulla with a maximum diameter of 8 cm in the right middle lobe; he subsequently underwent bullectomy. Histopathology revealed that pulmonary parenchyma adjacent to the bulla represented nodular proliferation of clear cells characterized by a papillary structure resembling placental chorionic villi. Immunohistochemically, clear cells were positive for CD10, suggesting placental transmogrification of the lung (PTL). We reviewed 36 surgical cases of PTL, and only 2 cases (5.6%), including our case, were operated for spontaneous pneumothorax. Bullous lesions secondary to PTL tend to appear as unilateral large cystic masses in non-upper lobes, which is atypical for primary spontaneous pneumothorax (PSP). Although PTL is considered a very rare cause of secondary pneumothorax, we must carefully differentiate this condition.