Pulmonary metastasis of endometrial stromal sarcoma

Multiple round opacities suggestive of metastatic lung tumors were incidentally found on a chest x-ray film in a 43-year-old woman. The patient underwent hysterectomy for "myoma uteri" three years previously. Extensive examinations could not specify the primary neoplastic lesions. Morphological characteristics of the thracoscopically resected lung tumors suggested low-grade endometrial stromal sarcoma (ESS), and immunostaining revealed that the tumor cells were positive for progesterone and estrogen receptors, CD10 and vimentin, confirming a diagnosis of ESS. ESS is an uncommon uterine neoplasm, however, may be mistaken as benign tumors such as epithelioid leiomyoma, and occasionally metastasizes to remote organs such as lungs even after long disease-free period, posing diagnostic challenge.