Is There a Baby in the Lung? A Case of Placental Transmogrification of the Lung

Abstract

Pulmonary nodules are commonly encountered in pulmonary practice. Etiologies could include infectious, inflammatory, and malignant. Placental transmogrification of the lung is an extremely rare etiology of pulmonary nodules. Such condition often presents as unilateral lesions in asymptomatic men. In general, such nodules are generally stable and grow extremely slowly. We highlight an unusual case of placental transmogrification of the lung (PLC) identified in a young female. The patient’s bilateral nodules were larger than what has been previously cited in the literature and exhibited growth over an 8-year follow-up period.

Introduction

Placental transmogrification of the lung (PTL) is an extremely rare etiology of pulmonary nodules first described in 1979 with less than 40 cases reported worldwide.^1,2 Placental transmogrification of the lung primarily affects males and has been described as a unilateral lesion that ranges in size from 0.5 to 15 cm with lung tissue that morphologically resembles immature placenta. ³ Radiographic findings can include both emphysematous and nodular lesions such as hamartomas. ⁴

Case Report

A 24-year-old female with no significant past medical history was admitted to the hospital for sepsis secondary to group A Streptococcus pharyngitis. Initial chest computer tomography (CT) revealed bilateral peripheral calcified and non–calcified cavitary lesions that ranged from 0.4 to 0.9 cm (Figure 1). Evaluation for endocarditis with both a transthoracic and transesophageal echocardiogram was negative. A biopsy was not pursued as the etiology of the nodules was suspected to be secondary to infectious etiology. She was discharged on antibiotics with close outpatient monitoring. A follow-up CT scan of the chest performed 2 months later revealed unchanged pleural-based parenchymal densities. She was lost to follow up. Five years later following an admission for a motor vehicle accident, CT of the cervical spine demonstrated further enlargement of nodule sizes. Infectious and inflammatory serology was negative. Chest CT scan showed multiple new bilateral solid lung nodules, the largest of which was in the right lower lobe and measured 2.3 × 2.0 × 1.6 cm (Figure 2). The cavitary lesions seen 5 years prior have increased in size and number, prompting a biopsy. Computer tomography–guided core biopsy of the lesion revealed lung with a variable mixture of hyaline cartilage, entrapped respiratory epithelium, and fibromyxomatous stromal changes (Figure 3). The pathology report described a hamartomatous-like process with placental villi-like structures and cartilage, with positive epithelial lining for TTF1 and negative for placental markers (Pattern of placental alkaline phosphatase [PLAP], Human placental lactogen [HPL], and Human Chorionic Gonadotrophin [HCG]). These histologic and immunohistochemical features were suggestive of a benign hamartomatous process described as “placental transmogrification” of the lung. The patient continued to follow up at the pulmonary clinic over the next 3 years, where she remained asymptomatic and frequent surveillance CT scans revealed stable pulmonary nodules.

Figure 1.

Axial computed tomography scan of the chest showing a 0.9-cm peripheral lesion.

Figure 2.

Multiple bilateral nodules, the largest of which is 2.3 cm in the greatest dimension. Notably, the previously seen peripheral nodule has grown and is portraying a more prominent cavitary component.

Figure 3.

Histopathological observations of the lesion. (A) (40×) presents a broad overview of the lesion, with minimal adjacent lung tissue visible on the right. (B) (100×) reveals the existence of hyaline cartilage (star). (C) (200×) exhibits a close-up view of the lesion, showcasing a fibromyxoid background with structures resembling placental villi (arrow). (D) (100×) demonstrates the presence of trapped respiratory epithelium (arrowhead).

Discussion

Placental transmogrification of the lung is described as a rare and generally benign disease of the lung characterized by its striking resemblance to placental tissue. Histologically and morphologically, PTL reportedly resembles placental chorionic villi and tissue while bearing none of the biological or biochemical properties of the placenta. ³ In a comprehensive systemic review of 34 published cases, PTL was reported to predominantly affect middle-aged males between the ages of 20 and 50, nearly half of whom were smokers. ² Clinical presentation of these patients varied from asymptomatic to a blend of cardiovascular and pulmonary symptoms that most often presented as chest tightness, cough, and dyspnea. Interestingly, although all 34 of these patients presented with unilateral lesions that ranged from 0.5 to 15 cm, our patient presented with bilateral lesions suggesting variability in previously known radiographic findings of the disease. ² Kim et al have classified the radiological findings into 3 radiographical patterns: the most frequently encountered is bullous emphysema; followed by a combined pattern of thin-walled cystic lesions and nodules; and solitary nodular pattern. ⁵

Although initially thought to be a histologic variant of unilateral bullous emphysema, recent genotypical findings suggest that the clear cell component of such lesions may play a role in the underlying pathogenesis. ³ Regardless, the pathophysiology and etiology of PTL are not completely understood. Although PTL is generally considered a benign lesion, Hano et al reported a case of malignant transformation of PTL to papillary adenocarcinoma. ⁶ Given the rarity of the disease, there are no clear-cut guidelines regarding optimal treatment modalities or frequency of surveillance; however, some authors recommend resection when patients are symptomatic. ⁷ Notably, a recent comprehensive review of the literature by Shiraishi et al reported that patients were more likely to require surgical intervention for symptomatic giant bullae than for pneumothorax. ⁸ The authors also suggested that histological examination after surgical intervention for pneumothorax could be justified if atypical findings were found on CT scans. ⁸

Our patient’s clinical presentation was unconventional in nodular growth, bilateral involvement, and the fact that it affected a female when the condition has been described to more commonly affect males. ² Our approach to such a rare entity emphasizes therapeutic relationships and shared decision-making. Throughout her follow-up period, transparently explaining the rarity of the condition and the lack of available clinical guidelines for directing management contributed to higher comfort levels with close observation rather than intervention. Thereafter, we initially agreed on performing surveillance CT scans every 3 to 6 months with attention to close follow-up. Given her relative stability and absence of symptoms, the frequency of surveillance CT scans was initially liberated to every year, then every 2 years. Notably, integrating such a shared decision-making process in patients with rare diseases has been reported to strengthen both the patient’s and the physician’s positions in the therapeutic relationship. ⁹

We shed light on an extremely rare phenomenon that should be considered and ruled out in patients who present with unilateral bullous lesions and who do not have risk factors for emphysema. Our patient’s presentation was unusual, given the gender predisposition and degree of nodular growth. Up to the author’s knowledge, our case is the first case documenting active PTL growth over a prolonged follow-up period.