Low-Grade Endometrial Stromal Tumors of the Uterus: Endometrial Stromal Nodule and Endometrial Stromal Sarcoma

摘要

Endometrial stromal tumors are uncommon uterine mesen-chymal neoplasms that are occasionally discovered in endometrial biopsy/ curettage specimens or in hysterectomies. Typical examples are composed of cells that resemble proliferative-phase endometrial stromal cells. The tumor cells have monotonous hyperchromatic nuclei and scanty cytoplasm. An immunohistochemical stain for CD 10 is generally positive, whereas stains for smooth muscle markers such as smooth muscle actin, desmin, and caldesmon tend to be negative or show only weak staining. Low-grade endometrial stromal tumors are either benign endometrial stromal nodules or low-grade malignant endometrial stromal sarcomas. Differentiation between these possibilities usually requires that the patient have a hysterectomy because the main differential diagnostic criterion is the presence or absence of myometrial invasion, and this usually cannot be assessed in a biopsy/curettage specimen. Rare variants of endometrial stromal tumors have a fibromyxoid or myxoid appearance or contain an admixture of smooth muscle cells. These variants, an example of which is presented in this case report, can be difficult to diagnose because they do not have the typical microscopic appearance of an endometrial stromal tumor or because the immunophenotype varies from the expected expression pattern, In addition to differentiating between endometrial stromal nodule and endometrial stromal sarcoma, the pathologist must differentiate both of these tumors from a highly cellular or epithelioid leiomyoma, which can occasionally mimic a stromal tumor.