Metastatic endometrial stromal sarcoma of the lung: Importance of immunohistochemical staining, clinical history and imaging studies

Proper evaluation of lung nodules is a difficult issue for clinical management of patients. Discriminating metastatic endometrial stromal sarcoma (ESS) from other primary spindle cell neoplasms of the lung using histological analysis can be challenging. This is particularly true when an adequate clinical history is lacking, because ESS metastasis can be delayed by a couple of decades. To emphasize the importance of the correlation of pathological findings with clinical history and imaging studies, we investigated 11 cases of ESS (seven low grade and four high grade) metastatic to the lung. All cases presented with one to multiple unilateral or bilateral lung nodules that were detected by chest computed tomography. Primary ESS was diagnosed from hysterectomy specimens except for one by endometrial biopsy, 0.5 to 23 years prior to metastasis. Immunohistochemical studies showed that all ESS cases were moderately to strongly positive for Bcl-2 and CD10 with > 50% of tumor cells stained, except for one high grade ESS that was negative for CD10. Eight (72.7%) and seven (63.6) of the 11 cases showed positive estrogen and progesterone receptors, respectively, with a majority of positive cases showing diffuse and moderate to strong staining. Strong but patchy staining for CD34 was detected in one (9.1%) case with smooth muscle differentiation. CK7 and TTF-1 were negative in all cases. Two (18.2%) cases exhibited patchy and strong positivity for caldesmon. Two (18.2%) low grade ESS cases showed moderate to strong AE1/AE3 positivity in > 50% of tumor cells, one of which also showed moderate CK19 and Cam 5.2 staining in >30% of tumor cells. One should be cautious when assessing spindle cell neoplasms of the lung in women with a history of hysterectomy. Correlation of clinical history and imaging studies with histological and immunohistochemical findings is essential to diagnosis of metastatic ESS to the lung.