Endometrial stromal sarcoma – the new genetic paradigm

Endometrial stromal sarcoma (ESS) is a gynaecological sarcoma that is composed of cells that resemble those of proliferative‐phase endometrial stroma. The 2014 World Health Organization tumour classification system separates ESS into low‐grade and high‐grade types, which are histologically, genetically and clinically distinct from undifferentiated uterine sarcoma (UUS). Low‐grade ESSs frequently contain chromosomal rearrangements that result in JAZF1–SUZ12 fusion or equivalent genetic fusions. Although most low‐grade ESSs show classic histological features that closely resemble those of proliferative‐phase endometrial stroma, there are several histological variants that are associated with the same genetic fusions as seen in the classic type. High‐grade ESS is defined by the presence of YWHAE–NUTM2A/B (YWHAE–FAM22A/B) fusions. High‐grade ESSs are clinically more aggressive than low‐grade ESSs, but are associated with a lower mortality rate than UUSs. The histological and immunophenotypic features of these different types of ESS, and their diagnostic considerations, are the subjects of this review.     

Prognostic indicators in WHO 2003 low‐grade endometrial stromal sarcoma

Aims: Endometrial stromal sarcoma (ESS) has traditionally been divided into low and high grade, but the World Health Organization (WHO, 2003) has changed the definition. Since 2003, many studies have used the old criteria, and few have focused on WHO 2003‐defined ESS low grade (ESS‐LG). The aim of this study was to investigate prognosticators in ESS‐LG. Methods and results: We reviewed the WHO 2003 diagnostic criteria in 91 tumours (previously classified as ESS low and high grade). There were 68 cases of ESS‐LG and 23 of undifferentiated endometrial sarcoma (UES). In the ESS‐LG cases, the prognostic value of clinicopathological variables was studied. With a median follow‐up of 79 months (range: 20–474 months), the recurrence and death rates were 5/68 (7%) and 1/68 (1.5%) in the ESS‐LG cases. Ovarian preservation or no ovarian preservation (P < 0.0001, hazard ratio (HR) 10.4) and mitotic activity index (MAI) (0–3 versus >3, P = 0.005, HR 8.6) had independent prognostic value. Other frequently used MAI thresholds – age, tumour diameter, and vessel invasion – were not prognostic. Among patients without ovarian preservation (n = 61), none of 53 with MAI 0–3 suffered recurrence, contrasting with two of eight (25%) of those with MAI >3 (P = 0.003); one of these two recurrence patients died (P = 0.02). Among patients with ovarian preservation (n = 7), three (43%) suffered recurrence but none died, and MAI had no additional prognostic value. Conclusions: In ESS‐LG, ovarian preservation and MAI >3 are associated with increased risk of recurrence.     

Cytogenetic and molecular aberrations in endometrial stromal tumors

Endometrial stromal tumors (ESTs) are rare uterine mesenchymal tumors, comprising <10% of all uterine mesenchymal neoplasms. The latest World Health Organization classification divides endometrial stromal tumors into 3 categories based on morphologic features: endometrial stromal nodule (ESN), low-grade endometrial stromal sarcoma, and undifferentiated endometrial sarcoma. Specific cytogenetic aberrations and molecular genetic alterations have recently been identified in endometrial stromal tumors, providing insights into their molecular biology, potential diagnostic markers, and possible therapeutic targets. Currently, recurrent chromosomal rearrangements resulting in gene fusion play a substantive role in the pathogenesis of endometrial stromal nodules, endometrial stromal sarcomas, and a small subset of undifferentiated endometrial sarcomas. Loss of heterozygosity of tumor suppressor genes and deregulation of the Wnt signaling pathway have also been implicated in EST tumorigenesis. In this review, we summarize the recent advances in the molecular pathology of endometrial stromal tumors.     

New developments in endometrial stromal sarcoma

Endometrial stromal tumours have been recently reclassified in the WHO 2014 Classification due to the discovery of new genetic fusions. This has enabled the subdivision of previously described undifferentiated endometrial sarcomas into the molecularly-defined high grade endometrial stromal sarcoma (HG ESS) and undifferentiated uterine sarcoma (UUS). In this review, we discuss the discoveries behind the 2014 Classification and its rationale, and give practical tips for diagnosis of these neoplasms, as well as discussing the differential diagnoses that one may consider.     

Molecular genetic changes in epithelial, stromal and mixed neoplasms of the endometrium

Endometrial carcinoma, endometrial stromal tumours and mixed malignant mesodermal tumours (MMMT) develop along distinctive molecular genetic pathways. Two distinctive types of endometrial carcinoma are distinguished, type I and type II, which develop along distinctive pathways and show different clinical behaviour and histological features. Type I carcinomas show endometrioid histology, are oestrogen-related and develop from atypical endometrial hyperplasia. The molecular tumorigenesis is comparable to colorectal carcinoma with a step-like progression and an accumulation of genetic alterations. Alterations of PTEN, K-Ras mutations and microsatellite instability are frequent and early events in type I carcinoma, whereas p53 mutations occur during progression to grade 3 carcinoma. Serous and clear cell carcinomas are considered type II carcinomas which are mostly unrelated to oestrogen. p53 mutations occur in almost all serous carcinomas and seem to occur early, leading to massive chromosomal instability and rapid tumour progression. Gene expression profiling has supported this dualistic model of endometrial carcinoma. There is evidence of molecular differences between serous and clear cell carcinomas as well as between endometrioid carcinomas with and without microsatellite instability. A dualistic model of tumorigenesis may be also suggested for endometrial stromal tumours. Endometrial stromal sarcomas (ESS; type I endometrial sarcoma) are oestrogen-related and seem to develop from endometrial stromal nodules (ESN). They are histologically and genetically distinct from undifferentiated endometrial sarcoma (UES) which seem to be mostly unrelated to oestrogen (type II endometrial sarcoma). ESS and ESN share the fusion gene JAZF1/JJAZ1 caused by a t(7;17)(p15;q21) translocation, whereas UES lacks a distinctive molecular alteration so far. In MMMT, which is considered a metaplastic carcinoma, p53 alteration occurs early, before clonal expansion and acquisition of genetic diversity during progression.     

Mixed endometrial stromal and smooth muscle tumor: Report of a case with focal anaplasia and early postoperative lung metastasis

A rare case of a mixed endometrial stromal and smooth muscle tumor arising in the uterus of a 74‐year‐old woman is reported. The patient underwent hysterectomy for an enlarging uterine mass, and a large intramural tumor, showing marked central hyaline necrosis with calcification, was found. The tumor consisted of an admixture of a low‐grade endometrial stromal sarcoma (ESS) and a fascicular proliferation of spindle cells suggesting smooth muscle differentiation, and a characteristic ‘star‐burst’ appearance was found. In the ESS region, there were a few small foci of anaplasia where large polygonal cells with atypical nuclei and abundant eosinophilic cytoplasm proliferated, and the proliferative activity was locally increased in these foci. A small metastatic nodule appeared in the lung nine months after the hysterectomy, and the resected metastatic lesion showed features of anaplastic spindle cell sarcoma which was immunoreactive for CD10 but not for smooth muscle markers. Mixed endometrial stromal and smooth muscle tumors should be regarded as malignant neoplasms with the potential for hematogenous metastasis, particularly when they contain foci of cellular anaplasia.     

子宫内膜间质肉瘤与转移复发瘤的形态特点

目的探讨子宫内膜间质肉瘤(ESS)和转移复发瘤组织形态与免疫组织化学染色特点,及其肿瘤分化特点和鉴别诊断。方法观察15例子宫原发ESS及4例转移复发瘤的组织形态,并用免疫组织化学EnVisonTM二步法检测CD10、平滑肌肌动蛋白(SMA)、雌激素受体(ER)、孕激素受体(PR)、AE1/3及α-抑制素的表达,以10例富于细胞平滑肌瘤作对照。结果15例患者发病年龄22～75岁(平均45岁)。组织学分型:7例经典型,3例平滑肌分化型,2例纤维黏液型,3例分化差型,细胞异型明显。4例复发转移瘤中3例组织形态与原发瘤不同。免疫组织化学染色阳性结果:在14例ESS及4例复发转移瘤中CD1015/18、SMA5/18、ER7/18、PR10/18;AE1/3和α-抑制素仅在腺样分化区阳性。平滑肌瘤对照组CD10为1/10、SMA为10/10,表达差异均有统计学意义(P<0.05)。结论ESS多向分化的特点使其呈现多样的组织形态,且转移复发瘤形态可与原发瘤不同。CD10与SMA联合应用有助于ESS的诊断和鉴别诊断。     

CD10 is a sensitive and diagnostically useful immunohistochemical marker of normal endometrial stroma and of endometrial stromal neoplasms

AIMS: The CD10 antigen is expressed in acute lymphoblastic leukaemia and follicle centre cell lymphoma. A recent study investigating the expression of CD10 in a wide range of non-haematopoietic neoplasms found positive staining in a small number of endometrial stromal sarcomas as well as in normal endometrial stroma. The present study aimed to ascertain whether CD10 positivity is indeed found in normal endometrial stroma and endometrial stromal neoplasms. Staining of a range of tumours which can be confused morphologically with endometrial stromal neoplasms was also undertaken to ascertain whether antibodies against CD10 are of value in a diagnostic sense. METHODS AND RESULTS: Neoplasms included in the study were endometrial stromal nodule (n=1), low-grade endometrial stromal sarcoma (ESS) (n=13), high-grade ESS (n=6), mixed endometrial stromal-smooth muscle tumour (n=1), uterine cellular leiomyoma (n=10), uterine leiomyosarcoma (n=5), adult granulosa cell tumour (AGCT) (n=10), undifferentiated endometrial carcinoma (n=6), uterine carcinosarcoma with an endometrial stromal component (n=1) and type II uterine mesenchymal tumour with sex cord-like elements (n=1). Cases of proliferative (n=5), secretory (n=5) and atrophic (n=3) endometrium were also stained. There was positive staining of stroma but not of glands in all cases of non-tumorous endometrium. There was positive staining of the endometrial stromal nodule and of all low-grade ESS. Staining in these varied but was often diffuse and of moderate to strong intensity. There was positive staining of four of six high-grade ESS, but this was usually focal. There was also positive staining of the endometrial stromal component in the mixed endometrial stromal-smooth muscle tumour and in the uterine carcinosarcoma. Most cellular leiomyomas were completely negative although three exhibited weak positivity. There was some positivity, usually focal or weak, of three of five leiomyosarcomas. Most AGCT and undifferentiated carcinomas were completely negative although one case of each exhibited focal staining. There was focal staining of the type II uterine mesenchymal tumour with sex cord-like elements. CONCLUSION: CD10 is a reliable and sensitive immunohistochemical marker of normal endometrial stroma. Positivity, which is often strong and/or diffuse is found in endometrial stromal nodules and low-grade ESS. Positive staining with CD10, when strong and diffuse, may be useful in distinguishing these tumours from histological mimics, especially cellular leiomyoma and AGCT which are generally negative. In this situation, CD10 should be used as part of a panel which might include desmin and alpha-inhibin depending on the differential diagnosis considered. Positive staining with CD10 in a high-grade uterine sarcoma which is negative with muscle markers might indicate endometrial stromal differentiation and identify a group of neoplasms which it is correct to diagnose as high-grade ESS rather than undifferentiated uterine sarcoma.     

Expression of androgen receptors in benign and malignant endometrial stromal neoplasms

Several studies have shown that endometrial stromal neoplasms express estrogen and progesterone receptors (ER, PR). To our knowledge, the presence or absence of androgen receptors (AR) in these rare uterine neoplasms has not been investigated. Tumors (n=20)—3 endometrial stromal nodules, 14 low-grade endometrial stromal sarcomas (ESS, low grade), and 3 high-grade endometrial sarcomas (undifferentiated endometrial sarcoma, UES)—were studied. Immunohistochemical analyses for ER, PR, and AR were performed on formalin-fixed, paraffin-embedded archival material. Positive immunoreactions for ER and PR were observed in 14 (70%) and 17 (85%) cases, respectively. Furthermore, 9 cases (45%) were positive for AR. Among 17 ESS and UES cases, 7 (41%) revealed positivity for AR. Two of three benign stromal nodules were also positive for AR. Moreover, one of the three high-grade sarcomas (undifferentiated endometrial sarcoma) was negative for both ER and PR, but showed positive reaction for AR. In summary, ARs are expressed in 45% of endometrial stromal neoplasms. In addition to determination of ER and PR, the results of immunohistochemical examination of AR in these rare uterine tumors may have some impact on the postoperative management of the patients.     

Pleomorphic high grade endometrial stromal sarcoma with YWHAE gene amplification may be a novel variant with poor prognosis

Endometrial stromal neoplasms are classified by the World Health Organization (WHO) into endometrial stromal nodule (ESN), low grade (LGESS), high grade (HGESS), and undifferentiated uterine sarcoma (UUS). HGESS is subclassified based on molecular findings, YWHAE or BCOR. The HGESS with YWHAE::NUTM2A/B (alias YWHAE::FAM22A/B) fusion usually have relatively monomorphic (as with most fusion-associated malignancies) rounded to epithelioid cells with eosinophilic cytoplasm, vesicular nuclei, nucleoli, and mitotic figures >10/10 HPF. We present a 66-year-old woman with post-menopausal bleeding found to have a heterogeneous solid-cystic uterine mass on CT who underwent total hysterectomy, bilateral salpingo-oophorectomy, omentectomy, and pelvic lymph node dissection. A 15.0×9.0 cm variegated uterine mass with hemorrhage and necrosis was identified. Histologically, the tumor was hypercellular with haphazard fascicles, microcysts, and tongue-like destructive myometrial invasion. Tumor cells exhibited marked pleomorphism and high mitotic activity with atypical mitotic figures. There was extensive cyclin-D1 and subset CD10 immunopositivity. FISH showed YWHAE amplification but without rearrangement. Interestingly, we found only two other reported cases of pleomorphic HGESS with YWHAE gene amplification upon review of 259 cases from cBioPortal database, one of which was reported as carcinosarcoma with heterologous elements. Of note, all three YWHAE amplified cases were diagnosed at high-stage and succumbed to disease within six months. Our case appears to be the third case of YWHAE-amplified pleomorphic HGESS, possibly a new variant of uterine sarcoma with aggressive biologic behavior that needs further evaluation.     

Endometrial stromal tumor with limited infiltration and probable extrauterine metastasis: report of a case

Endometrial stromal nodule (ESN) is a tumor composed of cells closely resembling those of the endometrial stroma with minimal cytologic atypia. The most important criterion for the differential diagnosis from the endometrial stromal sarcoma (ESS) is a well-defined noninfiltrative expansile border. However, the definition of the ESN also includes a tumor with the presence of focal irregularities or fingerlike projections of the margin into the adjacent myometrium, none of which exceeds 2 to 3 mm. In some cases, however, it is difficult to differentiate marginal irregularities of ESN from "true invasion" of ESS. We described a case of extrauterine ESS that was associated with small intramyometrial stromal lesions with limited infiltration. The intramyometrial lesion could be definitionally categorized as ESNs. However, peritumoral fibroblastic band and inflammatory stromal reactions, irregular fingerlike projections, and multiple concurrent extrauterine ESS strongly suggested that these were small primary focus of ESS mimicking ESN. We propose that the patient with endometrial stromal tumor with limited infiltration should be more carefully followed than the usual ESN for possible metastasis and that a hysterectomy with meticulous histological examination of the specimen be performed before a diagnosis of primary extrauterine ESS is made, even in a case showing a grossly or radiologically normal uterus.     

Endometrial stromal sarcoma arising in vaginaEndometrial stromal sarcoma arising in vagina

Endometrial stromal sarcoma (ESS) arising in the vagina is an extremely rare extrauterine endometrial stroma sarcoma, with only 4 cases reported in the literature up to date. Here we report a case of neoplasm originating from vagina. A 32-year-old woman complained of intermittent vaginal bleeding especially after intercourse. A mass with a diameter of 1.0 cm was found in the middle and upper segments of the right posterior vaginal wall. Biopsy showed ESS. Total abdominal hysterectomy, unilateral salpingo-oophorectomy (right) and partial vaginectomy were performed. No ESS lesion was found in endometrium. The patient received six courses of platinum-containing combination chemotherapy after surgery and was free of tumor 18 months after the diagnosis of ESS. The diagnosis of ESS relies on pathologic examination. CD10 is the most useful immunohistochemical marker for the diagnosis of this tumor. The mainstay treatment of ESS is surgery. Local excision and ovarian retaining may be considered in premenopausal women.     

Mesenchymal tumours of the uterus. VII. A clinicopathological study of 60 endometrial stromal nodules*

Endometrial stromal nodules are well-circumscribed neoplasms composed of cells identical to those in low-grade endometrial stromal sarcoma and proliferative endometrium. The clinical and pathologic features of 60 endometrial stromal nodules were studied to determine their characteristics and behaviour. A follow-up of up to 16 years revealed that none of the 60 patients developed recurrences or died of her disease, indicating that circumscribed endometrial stromal tumours are benign. A number of specific features such as irregularities in the margin, high mitotic counts, and a glandular trend did not seem to alter the benign course of this lesion.     

Fibromyxoid variant of endometrial stromal sarcoma with atypical bizarre nuclei

Endometrial stromal sarcoma (ESS) is the second most common malignant uterine mesenchymal tumor. It affects women primarily in the perimenopausal age group. ESSs are morphologically heterogeneous. The distinction between uterine smooth muscle tumors such as cellular leiomyoma and myxoid leiomyosarcoma and low-grade ESS can be problematic when stromal sarcomas show prominent smooth muscle differentiation and abundant myxoid stroma, respectively. We herein present a rare case of fibromyxoid variant of ESS, which was misdiagnosed as hydropic leiomyoma on intraoperative frozen section examination. Grossly, the uterine mass consisted of intracavitary and intramural portions. The intracavitary portion with extensive hydropic degeneration mimicked a hydropic leiomyoma. In contrast, the intramural portion displayed an obvious tongue-like myometrial invasion. Histologically, the tumor consisted of both cellular (20%) and myxoid (80%) areas. In the cellular areas, oval to spindle-shaped tumor cells with bland nuclear features were found to surround concentrically a rich vascular network of arterioles, a characteristic of ESS. In addition, two relatively well-circumscribed nodular lesions showing atypical bizarre nuclei were identified in the myxoid area. Immunohistochemically, the tumor cells were diffusely and strongly positive for CD10. The present case indicates a wide morphological spectrum of ESS. Fibromyxoid variant of ESS should be considered in the differential diagnosis of intracavitary and/or intramural uterine mesenchymal tumors with myxoid differentiation. It is important to avoid confusion between fibromyxoid ESS and myxoid leiomyosarcoma because of the differences in their clinical course, treatment, and prognosis.     

Endometrial stromal sarcoma with endometrioid adenocarcinoma of the uterus: a case report

Endometrial stromal sarcoma (ESS) is a rare malignant neoplasm of the uterus. We report the first case of undifferentiated ESS (UES) coexistent with grade 1 endometrioid adenocarcinoma in a 73-year-old female who presented with irregular vaginal bleeding for 4 days after menopause 20 years. Imaging examination including Magnetic Resonance Imaging (MRI) demonstrated multi-node reflection in uterine cavity without metastatic lesions, and the endometrium essentially normal. Grossly, a grey-red breakable polypoid tumor of 4.5 × 3.0 ×2.0 cm was recognized in the posterior uterine wall with surrounding slight rough endometrium. Microscopically, the tumor was composed of a larger component of undifferentiated stromal sarcoma that was distinct from a smaller endometrioid adenocarcinoma. The separate components of the tumor could be supported in immunohistochemical studies. There was no sign of recurrence for postoperative 6 months.