We report a case of incipient pulmonary lymphangioleiomyomatosis (LAM) diagnosed by histopathological examination of excised lung. A 28-year-old woman was referred to our hospital because of recurrent left pneumothorax. Computed tomography showed no abnormality except for small bullae in the right middle lobe. She underwent video-assisted thoracoscopic surgery and we excised the apex of the left lung showing hypertrophic pleura. Microscopic examinations of the surgical specimen revealed multiple focal accumulations of small spindle-shaped cells stained positively with anti-HMB-45 antibody, specific for LAM. Furthermore, among these multiple lesions, vascular invasion of HMB-45 positive cells were observed, which demonstrates invasive and metastatic potential of LAM cells as previously reported. This case implicates a need for a careful pathological examination of excised specimens in female cases of surgically treated pneumothorax even though pre-operation or macroscopic examination shows no specific findings.