Pulmonary metastases in patients with low-grade endometrial stromal sarcoma. Clinicopathologic findings with immunohistochemical characterization.

Two cases of low-grade endometrial stromal sarcoma (ESS) presenting as cystic pulmonary metastases are reported. Both lung lesions were initially thought to represent examples of so-called mesenchymal cystic hamartoma. A diligent search of the past medical records in the first case revealed that a primary low-grade ESS of the uterus had been resected 27 years earlier. In the second case, a uterine tumor was seen by computed tomography scan and subsequent pathologic examination of the hysterectomy specimen established the presence of a low-grade ESS. Peritoneal metastases, present in both cases, also presented diagnostic problems until the uterine primaries were recognized. Immunoreactivity for desmin was detected in all primary and metastatic tumor sites examined. We conclude that ESS should be included among the desmin-positive spindle cell sarcomas and that metastatic ESS should be included in the differential diagnosis of "benign" mesenchymal cystic hamartoma of the lung.