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After reading the summary, try answering the three related multiple-choice questions below.
A 45-year-old woman with menometrorrhagia underwent hysterectomy for a clinical diagnosis of fibroids. A hysterectomy and bilateral salpingo-oophorectomy were received. The posterior myometrium was diffusely expanded by multiple soft, worm-like, yellow-tan fleshy masses.
Archive Case and Diagnosis:
This case first appeared as Performance Improvement Program in Surgical Pathology (PIP) 2009, case 19, and is endometrial stromal sarcoma, low grade.
Criteria for Diagnosis and Comments:
The slide shows a tumor composed of cells with uniform round to ovoid nuclei that have scant to moderate amounts of eosinophilic to amphophilic cytoplasm. These cells whorl around the prominent vascular component, which are evenly spaced and uniform in caliber throughout the neoplasm. The neoplastic cells invade the surrounding myometrium as variably sized rounded to irregularly shaped nests in a “finger-like” pattern of permeation. These features, in combination with the presence of lymphatic/vascular invasion are diagnostic of an endometrial stromal sarcoma, low grade.
Endometrial stromal tumors are neoplasms composed of cells that morphologically resemble non-neoplastic proliferative phase endometrial stroma that proliferate around numerous small blood vessels in a characteristic growth pattern. Endometrial stromal tumors are separated into benign and malignant categories, termed endometrial stromal nodule and endometrial stromal sarcoma respectively, based upon the presence or absence of an infiltrative border. In the current (2002) WHO classification scheme, there are two categories of endometrial sarcoma – low-grade and undifferentiated, which is based on differences in tumor morphology rather than mitotic activity. A low-grade endometrial stromal sarcoma (ESS) is a tumor composed of cells that morphologically resemble non-neoplastic proliferative phase endometrial stroma that infiltrates the surrounding myometrium and usually invades lymphatic/vascular spaces. In contrast, an undifferentiated endometrial sarcoma (undifferentiated uterine sarcoma) is a poorly differentiated sarcoma composed of cells with marked cellular atypia and numerous mitoses (including atypical forms) without evidence of differentiation towards a recognizable uterine component (endometrial stromal or smooth muscle).
In most cases, the morphologic appearance of the tumor cells and the growth pattern within the myometrium can distinguish ESS from leiomyosarcoma (LMS). In cases in which there is prominent lymphatic/vascular permeation by LMS, ESS may be considered. Although morphologic features such as the presence of a fascicular architecture (even in the intravascular component) help facilitate its recognition as a malignant smooth muscle tumor, a panel of antibodies including h-caldesmon, desmin and CD10 may be performed in difficult cases. The majority of ESS will be CD10 positive (diffuse)/h-caldesmon negative/desmin variable (but usually focally positive) and the majority of LMS will be h-caldesmon positive/desmin positive/CD10 variable (often positive). The main pitfalls to consider are that nearly half of LMS can be CD10 positive (sometimes diffusely) and rare ESS can be diffusely positive for desmin; however, ESSs are typically not h-caldesmon positive unless there are areas of smooth muscle differentiation (which tend to be bland and will not exhibit the degree of cellularity and nuclear pleomorphism that can be present in LMS).
A recurrent chromosomal translocation t(7;17)(p15;q21) is the most common cytogenetic abnormality in ESS. This translocation results in the formation of a chimeric gene (JAZF1-JJAZ1) and the production of a fusion mRNA, which can be detected by RT-PCR. Rearrangements of PHF1 at 6p21 have also been reported with generation of the fusion gene JAZF1-PHF1.
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