AnswerDiagnosisLymphangioleiomyomatosis (LAM).DiscussionLymphangioleiomyomatosis is a rare disease characterizedby abnormal proliferation of smooth muscle-like cells thatexhibit myomelanotic differentiation represented by actinand HMB45 coexpression. It develops almost exclusivelyin women of reproductive age [1, 2]. Although the preciseincidence and prevalence of LAM remain unknown, thisdisorder probably represents less than 1% of all diffuse lungdiseases [3].In the vast majority of cases, the initial manifestationsof LAM are pulmonary symptoms including dyspnea,chest pain, recurrent spontaneous pneumothorax, orchylous pleural effusion [4]. The diagnosis of LAM isusually made based on the above-mentioned typicalclinical features and imaging characteristics of diffusebilateral thin-walled cysts [5]. Extrapulmonary LAMinvolvement is uncommonly seen as a minor componentassociated with typical pulmonary lesions. The casereported here is unusual in that LAM manifested initiallyas massive extrapulmonary involvement including super-ficial lymphadenopathy, and the large retroperitoneal masswith diffuse nodal spread closely simulating malignantneoplasms such as lymphoma, gynecological malignancy,or retroperitoneal soft tissue sarcoma. In addition, smallpulmonary nodules, not typical of LAM [5], complicatedthe picture and raised the possibility of widespreadpulmonary metastases.Extrapulmonary LAM mostly affects three majorlocations: the posterior mediastinum, the upper retroper-itoneal areas close to the abdominal aorta, and the pelviccavity [6]. This unique tendency is due to the fact thatthese sites are particularly rich in lymphatic vessels andlymph nodes, and LAM cells have a peculiar proclivity toproliferate around the lymphatics and migrate along thesestructures. Supraclavicular involvement observed in thiscase is exceptional.Estrogen and progesterone are considered to play apotential etiological role in LAM development. This isprimarily suggested by the fact that LAM mostcommonly presents in women of reproductive age [1,2]. In addition, pregnancy or estrogen administration isreported to aggravate LAM [7], and patients are fre-quently advised to avoid pregnancy [7, 8]. LAM cells arereported to express estrogen and/or progesterone recep-tors in half of the cases, and hypersecretion of sexhormones during pregnancy may trigger overstimulation