The striking similarity between benign metastasizing leiomyoma and lymphangioleiomyomatosis is that they both affect young women. This observation underscores the importance of gender-dependent variables in disease and our lack of understanding of gender differences. Many researchers are currently investigating the link between disease and hormone levels in the body. The beneficial role of estrogens remains in question in pulmonary medicine, and further ongoing research should help to define the role of hormones in the lung.