Stromal fragments meaning6/26/2023 ![]() In addition, the stroma is less robust or expansile in appearance. In both instances, the total amount of endometrial stroma on the slide is less, resulting in smaller fragment size. The main pitfalls are distinction from aglandular functionalis (strips of endometrial stroma devoid of glands as a consequence of attenuation secondary to an underlying submucosal leiomyoma) in a reproductive woman and atrophic endometrial stroma lacking glands in a peri- or postmenopausal woman. 13 In general, the stroma also has an expansive, sheet-like growth such that glands, if present, appear at the periphery, when there is involvement of the endometrium. The first clue that a biopsy/curettage specimen harbors an endometrial stromal neoplasm is the finding of multiple fragments of tissue composed entirely or almost entirely of endometrial-type stroma ( Figure 2) in one study, most endometrial stromal tumors presented with fragments measuring >5 mm. 9, 10, 11, 12įull size image Recognition as an Endometrial Stromal Neoplasm (Biopsy/Curettage Specimen) The most common genetic aberration identified in ESNs, which is similarly identified in LGESS (discussed later), is t(7 17)(p15 q21). 8 Desmin and h-caldesmon are positive in areas of smooth muscle differentiation although occasionally areas of conventional stromal differentiation may be desmin positive, and if so, typically it shows a perinuclear cytoplasmic pattern of staining. 7 Immunohistochemistry for vimentin, CD 10, and actins as well as WT1, ER, and PR are typically positive (rarely tumors may be CD 10 negative). ESNs can show variant morphology, most commonly smooth muscle differentiation, 6 but unusual forms of differentiation including skeletal muscle may occur. The vessels are typically evenly spaced and uniform in caliber throughout the neoplasm however, occasionally large, thick-walled vessels may be present, although this is usually only a focal finding identified in only a minority of cases. These cells appear to whorl around the prominent vascular component, which resembles the spiral arterioles of non-neoplastic endometrium. The neoplastic cells of ESNs resemble proliferative phase endometrial stroma, being composed of cells with uniform round to ovoid nuclei that have scant to moderate amounts of amphophilic to eosinophilic cytoplasm. They are characterized microscopically by a well-circumscribed, pushing border ( Figure 1b) however, small irregularities present as lobulated or finger-like projections (<3 in number and <3 mm) into adjacent myometrium may occur. Cyst formation as well as ischemic-type necrosis and hemorrhage may be seen. They typically are well circumscribed and show a uniform tan to yellow, soft cut surface ( Figure 1a). They are frequently polypoid with protrusion into the uterine cavity but may be intra-myometrial (ranging up to 10 cm). 4, 5 They occur much more commonly in the corpus than in the cervix. Finally, a practical approach to the diagnosis of undifferentiated uterine sarcoma (UUS) will be presented.ĮSNs are defined as tumors with absent to at most minimal myometrial invasion (≤3 mm and <3 protrusions) and no vascular invasion. The salient features that help distinguish a LGESS from a uterine tumor resembling ovarian sex-cord tumor as well as high-grade endometrial stromal sarcoma, the latter a tumor recently reintroduced in the WHO classification will also be discussed. In addition, distinction of a stromal nodule from a low-grade endometrial stromal sarcoma (LGESS) and stromal sarcoma with limited infiltration in a hysterectomy specimen will be covered. In particular, a practical approach to the diagnosis of endometrial stromal neoplasia will be covered including recognition as a stromal process in a biopsy/curettage and distinction from a highly cellular leiomyoma. This review will focus on endometrial stromal tumors and those features that help in their distinction. Uterine mesenchymal tumors continue to be a challenge to diagnose due to their non-specific clinical presentation, often non-distinctive gross appearance, varied (and many times overlapping) morphologic appearance, and unsuspected pitfalls in immunohistochemical expression.
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