[Placentoid malformation of the lung as differential diagnosis of localized emphysema].

In a 50-year old patient with a long history of chronic obstructive airway disease and pulmonary emphysema, unusual solid spongious areas adjacent to bullous tissue were detected by bullectomia because of mediastinal displacement and dyspnoea on exertion. Pathological anatomical diagnosis showed villous framework in the marginal regions of bullous transformed parenchyma. According to pathognomonic histological finding the lesion is known as placentoid malformation or placentoid bullous transmogrification, respectively. This disease must be differentiated against rare cystic tumours such as alveolar adenoma or sclerosing haemangioma as well as congenital lesions e.g. adenomatoid cystic malformation. The lesion presented here includes hamartomatous features, such as the presence of leiomyomatoid proliferations of smooth muscle cells and fatty tissue embedded in the villous stroma. The clinically predominant emphysematous transformation of the adjacent lung tissue is pathogenetically the result of a valve formation in combination with unphysiological traction forces. The ectatic lymphatic vessels in peripheral tissue may perhaps be of etiological importance. According to former studies this may be an congenital malformation with progressive development. Resection of affected lung parenchyma seems to be curative: so far, no recurrences have been noticed.