Uterine Endometrial Stromal Tumors With Limited Infiltration: First Report of a Case Series Indicating Potential for Malignant Behavior.

The distinction between a uterine endometrial stromal nodule (ESN) and low-grade endometrial stromal sarcoma (LGESS) is based on the nature of the interface between the lesion and the surrounding myometrium and the presence or absence of vascular invasion. Most LGESS exhibit widespread irregular myometrial invasion with or without vascular invasion, whereas ESNs are well-circumscribed without vascular invasion. Tavassoli and Norris proposed that minor marginal irregularity (up to 3 protrusions, each <3 mm beyond the main mass) is allowable in an ESN and these criteria have been incorporated into the World Health Organization Classification. There is a small group of neoplasms with marginal irregularity greater than that allowable in ESN but without the widespread myometrial infiltration typical of most LGESS. Such neoplasms have been categorized as endometrial stromal tumor with limited infiltration but there have been no studies which have provided follow-up in this group of neoplasms. We aimed to determine the clinical behavior of this uncommon group of neoplasms. From a series of 19 endometrial stromal tumors with limited infiltration, mainly from consultation practice, we obtained follow-up information in 16 cases by contacting referring pathologists and clinicians. The patient age ranged from 32 to 84 yr (median: 54 yr) and follow-up ranged from 16 to 187 mo (median: 52 mo). Two of 16 patients (12.5%) developed metastatic disease to the small intestine and peritoneum (1 case-metastasis at 23 mo) and bone and lung (1 case-humeral metastasis at 135 mo; lung and sacral metastases subsequently). No patient died from disease during the follow-up period. A small percentage of endometrial stromal tumors with limited infiltration exhibit malignant behavior with distant metastasis. Such neoplasms should be regarded as potentially malignant and the term LGESS with limited infiltration is an appropriate designation.