A78-02 Endometrial Stroma-Lined Cystic Lesions in the Lung: A Rare Case Report

Abstract Introduction Cystic lung disease (CLD) encompasses multiple etiologies that all share the same features of causing thin-walled air-filled cysts to develop in the lung parenchyma. The differential diagnosis for CLD is broad, each with their own treatment and prognosis. Here we present a case of CLD development secondary to endometrial tissue in the absence of malignancy. Case Presentation A 45-year-old female presented to pulmonary clinic for evaluation of pulmonary nodules on Computed tomography (CT) chest. Subsequent biopsies of two separate lesions suggested the differential diagnosis of pulmonary adenofibroma, with positive staining for estrogen receptor (ER). She briefly started Tamoxifen therapy but discontinued it due to unpleasant side effects. Over the next three years, surveillance of lesions via CT chest demonstrated progressive cavitation and progression of nodules into thin-walled cysts and pseudocysts. She ultimately went on to develop recurrent pneumothorax (PTX) and underwent multiple wedge resections. Surgical biopsy of all affected areas demonstrated endometrial stroma-lined cystic lesions with estrogen receptor (ER) positivity. Molecular testing for endometrial stromal tumor was negative for any rearrangements. Pathology obtained from voluntary hysterectomy during this time was negative for any pathology. Overall, this was most consistent with endometrial stroma-lined CLD. Annual mammograms were benign. She was later started on Letrozole and has since been clinically stable without notable worsening of her lung findings on surveillance CT scans. Discussion To our knowledge, CLD secondary to endometrial tissue in the absence of malignancy is an exceedingly rare event. Thoracic Endometriosis Syndrome may present with lung cysts, although these lesions are typically unilateral and accompanied by endometrial tissue in the abdominal cavity. Here, we present a patient with numerous bilateral endometrial lung nodules that gradually developed into thin-walled cysts over the course of several years. This case not only documents the occurrence of this rare presentation but also provides novel insight into its progression. This abstract is funded by: None