Abstract Introduction Pulmonary benign metastasizing leiomyoma (PBML) is an exceedingly rare condition, with fewer than 200 reported cases worldwide, characterized by pulmonary nodules or masses. Its pathogenesis remains unclear, though prevailing theories suggest hematogenous or lymphatic spread of uterine smooth muscle cells post-myomectomy or hysterectomy. The current treatment of PBML mainly including surgical treatment and Gonadotropin-releasing hormone (GnRH) agonist treatment. Description A 30-year-old gravid female first developed a persistent dry cough at approximately 28 weeks gestation (April 2022). Postpartum evaluation revealed bilateral diffuse ground-glass opacities (GGO) on chest CT, with contrast-enhanced imaging excluding pulmonary embolism. Despite a week of antibiotic therapy yielding minimal improvement, her dyspnea persisted and progressively worsened. Subsequent imaging eight months ago demonstrated increased GGO density, accompanied by pulmonary function tests showing obstructive ventilatory impairment and reduced diffusion capacity, bronchodilator testing proved negative. Her medical history was notable for uterine curettage performed four years earlier and uterine fibroids identified during pregnancy. She denied tobacco use. Laboratory assessment revealed mild hypoxemia with otherwise unremarkable findings. Thoracic imaging demonstrated diffused, homogeneous GGO involving all lung zones without nodularity or septal thickening. Abdominopelvic CT confirmed the presence of uterine fibroids. Positron emission tomography with 2-deoxy-2- fluorine-18 fluoro-D-glucose integrated with computed tomography (18F-FDG PET/CT) didn’t show high radiotracer uptak, but fibroblast activation protein inhibitor (FAPI) PET/CT showed intense tracer uptake in the uterine, lung and lymph nodes, strongly suggesting metastatic dissemination. Transbronchial cryobiopsy (TBCB) revealed spindle cells expanding alveolar septa, without necrosis. Immunohistochemistry confirmed that these cells were smooth muscle cells (positive for α-SMA and desmin, negative for fibroblast-specific protein 1) and were likely derived from the uterus (positive for estrogen receptor (ER) and progesterone receptor (PR), and some positive for p16). Low proliferative activity (Ki-67: 2%), negative HMB45 staining, and positive CD34 and Masson trichrome staining indicated a benign lesion. Following multidisciplinary discussion (MDD), PBML was diagnosed based on clinicopathologic and imaging correlation. The patient was initiated on GnRH agonist therapy. At the 4-month follow-up, her symptoms showed no significant improvement. Discussion This case is the first to describe PBML presenting as diffuse homogeneous GGO, diverging from the classic radiological pattern of nodular lesions. The GGO likely reflects diffuse interstitial smooth muscle proliferation.This case expands the radiological spectrum of PBML and highlights the importance of including this disease in the differential diagnosis of female patients with unexplained diffuse GGO in both lungs and a history of uterine fibroids and induced abortion. This abstract is funded by: National Natural Science Foundation of China (No. 82200074)
Hu et al. (Fri,) studied this question.