Unilateral cystic lung anomalies are uncommon. We report a case of placental transmogrification of the lung in an adult, a condition with a peculiar histological pattern characterized by formation of placental, villus-like structures in the lung parenchyma.
A 23-year-old man with a history of asthma presented to our emergency department with a 3-month history of increasing shortness of breath, which worsened on the day of presentation and was accompanied by sudden-onset, sharp, left-sided pleuritic chest pain. The patient's medications included inhaled albuterol as needed. He worked in a chicken farm and denied the use of tobacco, alcohol, and illicit drugs. His family history was noncontributory.
The patient was comfortable at rest with unlabored respiration at a rate of 18 breaths per minute; blood pressure of 148/86 mm Hg; and pulse rate of 78 beats per minute. He was afebrile and had an oxygen saturation of 97% on room air. Physical examination revealed distant cardiac sounds, with regular rate and rhythm, and diminished breath sounds on the left without any wheeze or crackles. Findings from the rest of the examination were unremarkable.
A complete blood cell count, chemistry panel, arterial blood gases, and a1-antitrypsin levels were all normal. The patient's chest radiograph showed left bullous emphysema and pneumothorax (Figure 1). He was admitted to the ICU and underwent CT of the chest, which revealed multiple cystic spaces in the left lung, consistent with bleb and bullous formation (Figure 2).
The patient was evaluated by thoracic surgery, and the decision was made to resect the left lung bullae to allow reexpansion of the compressed right lung. The patient underwent flexible bronchoscopy, which revealed patent airways. On thoracotomy, he was found to have an emphysematous left lung without any viable-looking healthy lung tissue, as well as herniation into the right side of the chest (Figure 3). Complete herniation of the heart on the right was also noted. The patient underwent left pneumonectomy after an initial attempt at bullectomy. He did well postoperatively and was discharged on day 5.
The pathological examination of the excised specimen demonstrated pleural surface with multiple air- and fluid-filled blebs (0.5 to 5.7 cm). Numerous areas of pleural and parenchymal disruption with involvement of upper and lower lobes were noted. Grossly, the specimen had spongiform appearance, similar to that of a placenta. Cystic lesions were noted with epithelium-lined papillae, filled with smooth muscle, blood vessels, and lymphoid tissue. Areas of fibrosis admixed with vague papillary structures were also noted. The papillae were characterized by vascular channels, stromal cells, and smooth muscle bundles. The macroscopic and histological findings resembled those of placental villi (Figure 4).
The pathological diagnosis was giant bullous emphysema with placental transmogrification of the lung.
Unilateral cystic lung anomalies are uncommon. We report a case of placental transmogrification of the lung in an adult, a condition with a peculiar histological pattern characterized by formation of placental, villus-like structures in the lung parenchyma. It is so named because of its morphological resemblance to immature placental structures.
Giant bullae occupying the entire hemithorax are not frequently seen. Usually, there is bilateral lung involvement, and the condition is related to smoking. Uncommon causes, such as a1-antitrypsin deficiency, usually also manifest bilaterally and progress slowly. Our patient had unilateral disease with a rare histological subtype of bullous emphysema.
The presentation of placental transmogrification ranges from asymptomatic to clinically overt and is sometimes associated with other pulmonary diseases, such as chronic obstructive pulmonary disease, recurrent pneumothoraces, and bronchopneumonia. To our knowledge, only a few cases have been described in the literature.
Placental transmogrification of the lung was first described in 1979 by McChesney.1 The condition has also been reported in surgical literature.2,3 The Table describes the presentation and clinical course of select cases that have been reported in the literature.2-9
The pathogenesis of placental transmogrification is unclear. Hypotheses include congenital hamartomatous malformation and lymphatic or vascular proliferation in emphysematous lung parenchyma.10 Cavazza and associates11 reported that placental transmogrification is not primarily a variant of focal emphysema, but rather is a benign proliferation of immature interstitial clear cells and secondary cystic change. Only 1 unusual case of papillary adenocarcinoma has been reported to have arisen from placental transmogrification.9
Patients may remain asymptomatic for years or may present with decreased exercise tolerance, gradual shortness of breath, hemoptysis, or infections.5 Surgical resection is usually curative and is the treatment of choice. Surgical treatments have included lobectomy or pneumonectomy, depending on the extent of lung involvement. Video-assisted thoracoscopy with staple resection of bullae has also been described as a form of treatment.7
In conclusion, placental transmogrification of the lung should be considered in the differential diagnosis of any patient who presents with predominantly unilateral bullous lung disease, especially in the absence of other risk factors for emphysema.
McChesney T. Placental transmogrification of the lung: a unique case with remarkable histopathologic features.
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Fidler ME, Koomen M, Sebek B, et al. Placental transmogrification of the lung, a histologic variant of giant bullous emphysema. Clinicopathological study of three further cases.
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Xu R, Murray M, Jagirdar J, et al. Placental transmogrification of the lung is a histologic pattern frequently associated with pulmonary fibrochondrontous hamartoma.
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Cavazza A, Lantuejoul S, Sartori G, et al. Placental transmogrification of the lung: clinicopathologic, immunohistochemical and molecular study of two cases, with particular emphasis on the interstitial clear cells.