Lymphangioleiomyomatosis (LAM) is a systemic, progressive, and fatal condition affecting almost exclusively women in their reproductive years. LAM most often occurs as a sporadic disease, but also occurs in women with tuberous sclerosis complex (TSC) (syndromic LAM). There are no pathologic differences between sporadic and syndromic LAM. Sporadic LAM is a rare disease with prevalence of approximately 1 to 2 cases per million women in the United States and among populations of white descent, and is even rarer among Asian and African individuals. Syndromic LAM affects 4% to 5% of women with TSC. Sporadic LAM is often found also in association with renal angiomyolipoma, the most common sign of TSC, but LAM associated with angiomyolipoma does not define TSC. Although LAM is not diagnostic for TSC either in isolation or in association with angiomyolipoma, still it is considered by some researchers as an incomplete expression (forme fruste) of TSC. LAM may involve the lungs and the axial lymphatics and lymph nodes of the thorax and retroperitoneum. In sporadic LAM, thoracic, intraabdominal, and cervical lymph nodes can be involved with or without lung involvement. The diagnosis of LAM is often delayed. A case of LAM in a young lady, which was complicated with pleural and peritoneal chylous effusions, is presented. The diagnosis was first made on a retroperitoneal lymph node biopsy. The patient had a prolonged prior history of respiratory problems owing to lung involvement, and eventually died 2 years after diagnosis. Focus on the clinicopathologic diagnosis of TSC is also made.