肺胎盘样变形(placental transmogrification of the lung, PTL)是一种非常罕见的良性肺部病变, 国内外文献报道仅40多例, 影像和组织形态学表现多样, 多为单侧囊性病变, 少数为实性结节。由于实性PTL极为罕见, 大多数病理医生和外科医生对其认识不足。本研究报道1例位于前纵隔以实性结节为特点的PTL, 并结合文献复习, 以提高广大医生对这一罕见病的认识。患者为男性, 52岁, 无吸烟史, 无明显临床症状。体检胸部CT发现左肺下叶后基底段脊柱旁有一个圆形低密度灶, 最大径约2.9 cm, 于胸腔镜下行肺段楔形切除送检。大体形态: 肺膜下肺实质内类圆形结节, 大小3.0 cm×3.0 cm×1.6 cm, 切面灰白, 海绵状, 质软。镜下可见结节由乳头状结构组成, 低倍镜下形似胎盘绒毛。乳头轴心间质水肿, 粉染无定形物及钙盐沉积, 少量淋巴细胞浸润, 毛细血管充血明显; 其间可见形态温和的圆形细胞增生、聚集, 细胞质浅染或空泡状, 细胞核圆形或卵圆形, 与脂肪细胞移行过渡, 免疫组织化学染色CD10阳性; 乳头表面被覆单层立方上皮, 无异型性, 无核分裂象。术后患者随访1年, 无复发及不适。该病的发病机制目前尚不清楚, 有错构瘤、肺气肿变异和间质细胞克隆性增生等多种假说。结合本病例并在文献复习的基础上, 我们推测PTL的发病机制可能为, 肺泡间隔内不成熟间质细胞增生并向各类间叶细胞分化, 随着病变的不断发展, 因阻塞活瓣效应或增生组织的牵拉作用引起继发性囊性变, 最终出现典型的单侧囊性结节。外科手术是PTL确诊和治疗的唯一选择, 临床医生可依据临床表现、PTL发生的部位及范围制定个体化手术方案, 在完整切除病灶的同时尽量保留周围正常肺组织, 术后预后良好。

Placental transmogrification of the lung (PTL) is a very rare benign lung lesion. There are only about 40 cases reported in the literature. The imaging and histological features of PTL cases in the publication are various, most of which are cystic and a few of which are solid. Being extremely rare, the solid PTL is unknown to major pathologists and surgeons. We reported a case of solid PTL in the anterior mediastinum. The patient was a 52-year-old male with no history of smoking and without symptoms. During physical examination, chest CT revealed a circular low-density lesion with a maximum diameter of 2.9 cm beside the spine in the posterior basal segment of the left lower lobe of the lung. The wedge resection was performed by video-assisted thoracoscopy. Grossly, a round nodule was located underneath the visceral pleura. It was about 3.0 cm×3.0 cm×1.6 cm and the cut surface was grey-red, soft and spongy. Microscopically, the nodule was constituted of papillare, which resembled placental villi at low magnification. The axis of papillae was edema, in which some mild round cells with clear cytoplasm and CD10 positive staining aggregated and transitioned to immature adipocytes and amorphous pink materials deposited with a few of inflammatory cells infiltration. The surface of papillae was covered with disconti-nuous alveolar epithelium. Combined with the typical morphology and immunohistochemical characteristics of CD10 positive, the diagnosis was PTL. The patient was followed up for 1 year without recurrence and discomfort. So far, the pathogenesis of PTL is unclear. The major hypotheses include hamartoma, variant of emphysema and clonal hyperplasia of stromal cells. Based on the study of our case and publication, we speculate that the hyperplasia of stromal cells located in the alveolar septa might be the first step to form the solid PTL. With the progression of the disease, a typical unilateral cystic nodule develops as a result of secondary cystic degeneration due to the occlusive valve effect. Surgery is the only option for diagnosis and treatment of PTL. The clinician should make an individualized operation plan according to the clinical manifestations, location and scope of the lesion, and preserve the surrounding normal lung tissue as much as possible while completely removing the lesion. There is a favorable prognosis.