Refractory Pneumothorax Due to Cystic Pulmonary Metastasis of a Lowgrade Endometrial Stromal Sarcoma: A Case Report.

Low-grade endometrial stromal sarcoma (LG-ESS) is a rare uterine neoplasm. Computed tomography (CT) revealed the presence of multiple small bilateral pulmonary nodules in a 58-year-old woman 1 year after surgery for LG-ESS; the clinical diagnosis was pulmonary metastasis. Hormone therapy with progesterone was initiated, after which most of the solid nodules disappeared and some transformed into cystic lesions. Seven years after hormone therapy, the patient experienced repeated pneumothorax. The cause of the pneumothorax was perforation of a metastatic focus within the wall of a small subpleural cyst that was not evident on CT images.

Prognosis of uterine and extrauterine low-grade endometrial stromal sarcoma: an observational cohort study.

OBJECTIVE: Little is known about the survival differences between uterine and extrauterine low-grade endometrial stromal sarcoma (LGESS). Survival outcomes, consisting of disease-free survivals and overall survivals (OS), were compared in these two entities. METHODS: From February 2012 to June 2019, all primary LGESS cases and LGESS cases with first recurrence in the study center were reviewed. The clinicopathological characteristics and survival outcomes of extrauterine and uterine LGESS patients were compared for both primary and recurrent diseases. RESULTS: During the study period, 143 patients with primary LGESS and 56 patients with recurrent LGESS were included and followed up to 1 June 2020, among whom 8 (5.6%) and 10 (17.8%) patients were identified as having extrauterine LGESS. Patients with primary and recurrent extrauterine LGESS had similar clinicopathological characteristics to those of patients with uterine LGESS. In primary or in recurrent LGESS cases, in univariate analysis, patients with uterine and extrauterine LGESS had similar disease-free intervals after the last treatment, and they also had similar OSs after the diagnosis. Ovarian preservation led to significantly increased recurrence for primary LGESS [hazard ratio (HR) 4.9, 95% CI: 2.3-10.1, P <0.001) and repeated recurrence for recurrent LGESS (HR 3.1, 95% CI: 1.3-7.3, P =0.009). Surgical treatment for recurrent LGESS decreased repeated recurrence after the first recurrence (HR 0.2, 95% CI: 0.1-0.7, P =0.006). No factors were found to be associated with the OS of primary or recurrent LGESS. CONCLUSION: The clinical characteristics and survival outcomes of extrauterine LGESS are similar to those of uterine LGESS. Surgery is the treatment of choice for recurrent LGESS. Ovarian preservation is detrimental to disease-free survival but not to OS in both uterine and extrauterine LGESS.

Targeted RNA Sequencing Highlights a Diverse Genomic and Morphologic Landscape in Low-grade Endometrial Stromal Sarcoma, Including Novel Fusion Genes.

Low-grade endometrial stromal sarcoma (LGESS) represents a morphologically and genetically heterogenous mesenchymal neoplasm. Previous work has shown that approximately half of LGESS are characterized by JAZF1::SUZ12 gene fusions, while a smaller proportion involves rearrangement of other genes. However, a subset of cases has no known genetic abnormalities. To better characterize the genomic landscape of LGESS, we interrogated a cohort with targeted RNA sequencing (RNA-Seq). Cases previously diagnosed as low-grade endometrial stromal neoplasia (n=51) were identified and re-reviewed for morphology and subjected to RNA-Seq, of which 47 were successfully sequenced. The median patient age was 49 years (range: 19 to 85). The most commonly detected fusions were JAZF1::SUZ12 (n=26, 55%) and BRD8::PHF1 (n=3, 6%). In addition to the usual/typical LGESS morphology, some JAZF1::SUZ12 fusion tumors showed other morphologies, including fibrous, smooth muscle, sex-cord differentiation, and myxoid change. Novel translocations were identified in 2 cases: MEAF6::PTGR2 and HCFC1::PHF1 . Ten tumors (21%) had no identifiable fusion, despite a similar morphology and immunophenotype to fusion-positive cases. This suggests that a subset of cases may be attributable to fusion products among genes that are not covered by the assay, or perhaps altogether different molecular mechanisms. In all, these findings confirm that RNA-Seq is a potentially useful ancillary test in the diagnosis of endometrial stromal neoplasms and highlight their diverse morphology.

Highly malignant endometrial stromal sarcoma in a cat.

An 11-year-old female Persian cat underwent ovariohysterectomy due to dilation of the uterine cavity with irregular thickening of the wall. Macroscopically, the middle and distal regions of the left uterine horn were swollen and the uterine wall was irregularly thickened due to the development of multiple coalescent, variably sized nodules. Microscopically, the nodules had originated in the endometrium and were composed of round to polygonal neoplastic cells arranged in dense sheets or ill-defined fascicles. The neoplastic cells had locally invaded the myometrium and reached the subserosa, with lymphovascular invasion. Immunohistochemically, the neoplastic cell population was partially positive for CD10, an established marker of endometrial stromal sarcoma (ESS) in humans, with focal and diffuse nuclear immunopositivity for oestrogen and progesterone receptors and immunonegativity for desmin and α-smooth muscle actin. Based on these findings, the uterine tumour was diagnosed as ESS and was considered to correspond morphologically to high-grade ESS in humans.

Uterine MEIS1::NCOA2 Fusion Sarcoma With Lung Metastasis: A Case Report and Review of the Literature.

MEIS1::NCOA1/2 fusion sarcomas are a recently described novel entity arising in a variety of locations with a predilection for the genitourinary tract and gynecologic organs. Despite multiple locoregional recurrences, these tumors are thought to behave in a low-grade malignant manner. Here we report a uterine MEIS1::NCOA2 fusion sarcoma with lung metastasis. The patient was a 47-yr-old woman with a history of abnormal uterine bleeding who was found to have a myometrial mass confirmed by pathology to be uterine sarcoma. The tumor was predominantly composed of monotonous spindle cells with scant cytoplasm, crowded nuclei, and brisk mitotic activity, growing in a fascicular and streaming pattern. The morphologic and immunophenotypic features were nonspecific and a diagnosis of high-grade uterine sarcoma with a differential of leiomyosarcoma versus high-grade endometrial stromal sarcoma was rendered. At the 27-mo follow-up, the patient was found to have a lung metastasis consisting of a monotonous round cell sarcoma. A retrospective RNA-based and DNA-based next-generation sequencing of the primary uterine sarcoma revealed a MEIS1::NCOA2 gene fusion, a c.94G>C/p.D32H mutation in exon 3 of CTNNB1 gene, HMGA2 , and CDK4 gene amplification, and an intermediate/marginal level of MDM2 gene amplification. Polymerase chain reaction-based molecular analysis further demonstrated that the MEIS1::NCOA2 gene fusion and CTNNB1 somatic mutation were also present in the lung metastasis. This case represents the first case of such gynecologic sarcoma with distant (lung) metastasis, and the second metastatic case among all reported MEIS1::NCOA1/2 fusion sarcomas, highlighting the malignant metastatic potential of this emerging entity. Our case also indicates that HMGA2/CDK4/MDM2 region amplification and CTNNB1 somatic mutation might be recurrent genetic events in this rare sarcoma subtype.

Endometrial/Endometrioid Stromal Tumors With Extensive Whorling and CTNNB1 Translocation : A Report of 3 Cases.

Endometrial/endometrioid stromal tumors are rare and morphologically heterogenous, and their diagnosis may be challenging. We identified 3 endometrial/endometrioid stromal tumors with identical and previously undescribed histologic features and herein report their morphologic, immunohistochemical, and molecular profiles. Patients were 53, 62, and 79 years. Tumors were well-circumscribed, tan-yellow solid masses measuring 10.0, 11.0, and 18.7 cm, and were intramyometrial (n=2) or in the broad ligament (n=1). All showed small, tight whorls of epithelioid to slightly spindled tumor cells with minimal cytoplasm and negligible mitoses, multifocally associated with hyalinization and myxoid change set in a loose fibroblastic background with small, delicate vessels. This morphology was seen throughout in 1 tumor and in ∼20% and 70% of the 2 others with the remaining areas showing sex cord-like differentiation. Tumor cells expressed CD10 (3/3, 1 focal), calretinin (3/3 diffuse), WT1 (3/3 diffuse), estrogen receptor (1/1, diffuse). RNA-sequencing was successful in 1 tumor and revealed a GREB1-CTNNB1 in-frame fusion. All 3 tumors harbored a CTNNB1 translocation by fluorescence in situ hybridization correlating with nuclear ß-catenin expression. Whole-genome DNA methylation analysis classified all 3 tumors within the low-grade endometrial stromal sarcoma reference class with flat copy number profiles. One patient (79-y-old) died of unrelated causes 2 months after surgery and the other 2 were alive without disease after 13 and 75 months. We have described a rare subset of endometrial/endometrioid stromal tumors with extensive whorling and a CTNNB1 translocation, expanding the morphologic and molecular spectrum of these neoplasms.

Clinical features of uterine sarcomas presenting mainly with uterine masses: a retrospective study.

BACKGROUND: Uterine sarcomas are uncommon mesenchymal tumors of the uterus. The clinical problem is that the features of uterine sarcomas can sometimes mimic uterine fibroids. This study aims to investigate the clinical characteristics of patients with uterine sarcomas who were preoperative presenting mainly with uterine masses. METHODS: A retrospective analysis of patients who underwent gynecological surgery for uterine sarcomas at the Obstetrics & Gynecology Hospital of Fudan University, between January 2016 and December 2021. RESULTS: Over the 5-year period, 277 patients were final diagnosed of uterine sarcomas. A total of 162 patients were preoperatively diagnosed as uterine fibroids for surgical treatment, the majority of whom were diagnosed of uterine leiomyosarcoma (uLMS) (49/162) and low-grade endometrial stromal sarcoma (LG-ESS) (100/162). Ninety people underwent total hysterectomy and bilateral salpingo-oophorectomy (TH + BSO), while 72 underwent myomectomy followed by supplemental TH + BSO. The group with direct hysterectomy had a higher average age than the group with prior myomectomy (47.20 ± 8.94 vs. 40.86 ± 5.88, p < 0.001). Among patients preoperatively diagnosed as uterine fibroids, patients with uLMS had a higher proportion of previous myomectomy (26.53% vs. 5.00%, p < 0.001), a larger uterine mass diameter on ultrasound (8.38 ± 3.39 cm vs. 6.41 ± 1.92 cm, p < 0.001), and richer hypervascularity (34.69% vs. 18%, p = 0.024) compared with LG-ESS. CONCLUSIONS: Analysis of our data showed that a large proportion of uterine sarcomas, especially uLMS and LG-ESS, present mainly with uterine masses. Ultrasound features including a large uterine mass diameter and rich hypervascularity, and with a history of myomectomy may alert clinicians in suspicion of uLMS when compared with LG-ESS.

Clinical characteristics and prognostic factors of endometrial stromal sarcoma and undifferentiated uterine sarcoma confirmed by central pathologic review: A multi-institutional retrospective study from the Japanese Clinical Oncology Group.

OBJECTIVES: Low-grade and high-grade endometrial stromal sarcomas (LGESS and HGESS) and undifferentiated uterine sarcomas (UUS) are rare tumors whose pathological classification and staging system have changed recently. These tumors are reported to contain fusion genes. We aimed to clarify the genetic background, clinical features, prognostic factors, and optimal therapy of these tumors using a new classification and staging system. METHODS: We analyzed the clinical features and prognostic information of 72 patients with LGESS, 25 with HGESS, and 16 with UUS using central pathological review. Estrogen and progesterone receptors (PgRs) were examined by immunohistochemistry. JAZF1-SUZ12 and YWHAE-NUTM2A/B gene fusions were tested using real-time polymerase chain reaction. RESULTS: The 5-year overall survival (OS) rates of LGESS, HGESS, and UUS were 94%, 53%, and 25%, respectively. In LGESS, stage IV, incomplete surgery, and absence of PgR were associated with poor OS. The presence of JAZF1-SUZ12 fusion gene was not associated with OS. In HGESS, the relationship between stage and prognosis was unclear. None of the 3 patients with YWHAE-NUTM2A/B fusion gene died during follow-up. Adjuvant chemotherapy was associated with a favorable OS. Incomplete resection of UUS was associated with poor OS; however, residual tumors frequently occurred. Although most patients underwent adjuvant chemotherapy, their prognosis was extremely poor even in stage I disease. CONCLUSIONS: Prognosis of LGESS is generally good; however, stage IV, incomplete surgery, and PgR-negative tumors are associated with poor prognosis. Adjuvant chemotherapy may be useful for HGESS. Prognosis of UUS is extremely poor, even with adjuvant chemotherapy.

Prognostic factors, oncological treatment and outcomes of uterine sarcoma: 10 years' clinical experience from a tertiary care center in Pakistan.

BACKGROUND: Uterine sarcoma is an uncommon aggressive malignancy. Optimal management and prognostic factors have yet to be well recognized due to their rarity and various histological subtypes. This study aims to investigate these patients' prognostic factors, treatment modalities, and oncological outcomes. METHODS: A single-center retrospective cohort study was conducted on all patients diagnosed with uterine sarcoma and treated from January 2010 to December 2019 in a tertiary-care hospital in Pakistan. The data were analyzed using STATA software and stratified on the histological subtype. Survival rates were estimated using the Kaplan-Meier method. Crude and adjusted hazard ratios with 95% CI were estimated using univariate and multivariate analysis. RESULTS: Of the 40 patients, 16(40%) had uterine leiomyosarcoma (u-LMS), 10(25%) had high-grade endometrial stromal sarcoma (HGESS), 8(20%) had low-grade endometrial stromal sarcoma (LGESS) and 6(15%) had other histological subtypes. The median age of all patients was 49 (40-55.5). Thirty-seven (92.5%) patients underwent primary surgical resection, and 24 (60%) patients received adjuvant systemic chemotherapy. The survival plots showed the overall population's DFS of 64 months and the OS of 88 months (p-value = 0.001). The median DFS in all patients was 12 months, and the median OS was 14 months (p-value = 0.001). A small but significant DFS benefit was found in patients who received adjuvant systemic chemotherapy, 13.5 versus 11 months (p-value = 0.001). Multivariate Cox-regression analysis revealed that large tumor size and advanced FIGO stage were substantial factors associated with decreased survival. CONCLUSION: Uterine sarcomas are rare malignancies with poor prognosis. Multiple factors, including tumor size, mitotic count, stage of the disease, and myometrial invasion, impact survival outcomes. Adjuvant treatment may decrease the recurrence rate and improve DFS but do not affect OS.

Prognostic factors in patients with uterine sarcoma: the SARCUT study.

OBJECTIVE: Uterine sarcomas are a rare and heterogeneous group of malignancies that include different histological sub-types. The aim of this study was to identify and evaluate the impact of the different prognostic factors on overall survival and disease-free survival of patients with uterine sarcoma. METHODS: This international multicenter retrospective study included 683 patients diagnosed with uterine sarcoma at 46 different institutions between January 2001 and December 2007. RESULTS: The 5-year overall survival for leiomyosarcoma, endometrial stromal sarcoma, undifferentiated sarcoma, and adenosarcoma was 65.3%, 78.3%, 52.4%, and 89.5%, respectively, and the 5-year disease-free survival was 54.3%, 68.1%, 40.3%, and 85.3%, respectively. The 10-year overall survival for leiomyosarcoma, endometrial stromal sarcoma, undifferentiated sarcoma and adenosarcoma was 52.6%, 64.8%, 52.4%, and 79.5%, respectively, and the 10-year disease-free survival was 44.7%, 53.3%, 40.3%, and 77.5%, respectively. The most significant factor associated with overall survival in all types of sarcoma except for adenosarcoma was the presence of residual disease after primary treatment. In adenosarcoma, disease stage at diagnosis was the most important factor (hazard ratio 17.7; 95% CI 2.86 to 109.93). CONCLUSION: Incomplete cytoreduction, tumor persistence, advanced stage, extra-uterine and tumor margin involvement, and the presence of necrosis were relevant prognostic factors significantly affecting overall survival in uterine sarcoma. The presence of lymph vascular space involvement and administration of adjuvant chemotherapy were significantly associated with a higher risk of relapse.

Prognostic factors in undifferentiated uterine sarcoma: a subanalysis of the SARCUT study.

PURPOSE: The aim of this study was to analyze the prognostic factors related to the recurrence rate and overall survival of patients with undifferentiated uterine sarcoma. METHODS: An international multicenter study involving 43 international centers, the SARCUT study, collected 966 uterine sarcoma cases; among them 39 cases corresponded to undifferentiated uterine sarcoma and where included in the present subanalysis. The risk factors related to the oncological outcomes where analyzed. RESULTS: The median age of the patients was 63 (range 14-85) years. Seventeen (43.5%) patients presented FIGO stage I. The 5-year overall survival (OS) was 15.3% and 12-months disease-free survival (DFS) 41%. FIGO stage I was significantly associated with a better prognosis. In addition, patients who received adjuvant radiotherapy showed significant longer disease-free survival compared to those without adjuvant radiotherapy (20.5 vs. 4.0 months, respectively; p = 0.04) and longer overall survival (34.7 vs. 18.2 months, respectively; p = 0.05). Chemotherapy administration was associated with shorter DFS (HR 4.41, 95% CI 1.35-14.43, p = 0.014). Persistent disease after primary treatment (HR = 6.86, 95% CI 1.51-31.09, p = 0.012) and FIGO stage IV (HR 4.12, 95%CI 1.37-12.44, p = 0.011) showed significant worse prognosis for OS. CONCLUSION: FIGO stage seems to be the most important prognostic factor in patients with undifferentiated uterine sarcoma. Adjuvant radiotherapy seems to be significantly associated also to a better disease-free and overall survival. On the contrary, the role of chemotherapy administration remains unclear since was associated to a shorted DFS.

Uterine Endometrial Stromal Tumors With Pure Low-Grade Morphology Harboring YWHAE::NUTM2 Fusions: Report of a Case Series Emphasizing Potential for High-Grade Transformation and Aggressive Behavior.

Uterine endometrial stromal sarcomas (ESS) with YWHAE::NUTM2 gene fusions are typically morphologically high-grade tumors composed of atypical round cells, sometimes associated with a low-grade fibromyxoid component; they are currently included in the category of high-grade ESS (HGESS). We report 5 morphologically pure low-grade endometrial stromal tumors harboring YWHAE::NUTM2 fusions, including 1 endometrial stromal nodule (ESN) and 4 low-grade endometrial stromal sarcomas (LGESS), an association only occasionally reported previously. Patients ranged from 30 to 51 (mean=43) years and tumors from 4.5 to 7.5 cm (mean=5.7). All were stage I at diagnosis (confined to the uterus). Microscopically, the 4 LGESS showed extensive "tongue-like" invasion of the myometrium, and the ESN was entirely confined to the endometrium with no myometrial invasion. All tumors were composed entirely of morphologically uniform bland ovoid cells resembling proliferative endometrial stroma. A fibromyxoid component was seen in 1 LGESS and the ESN; in the LGESS, this was the sole component. Atypical round cells characteristic of YWHAE::NUTM2 HGESS were not identified. Mitotic count ranged from <1 to 13 per 10 high-power fields (mean: 3). CD10 was positive in 2/4 (focal), estrogen receptor in 5/5 (focal=1; diffuse=4), progesterone receptor in 5/5 (focal=1; diffuse=4) and cyclin D1 was diffusely positive in 3/4. Follow-up was available in all 5 patients and ranged from 6 to 159 months (mean=72). Two patients with LGESS had recurrent disease at 15 and 155 months; 1 showed predominantly LGESS with rare round cells in the initial recurrence and pure HGESS in a subsequent recurrence, while the other patient's recurrent tumor was predominantly HGESS (90%) in a background of focal fibromyxoid LGESS (10%). Both patients rapidly progressed and died of disease within 5 months of high-grade recurrence. We show that rare cases of morphologically pure low-grade endometrial stromal tumors, some but not all with a fibromyxoid component, harbor YWHAE::NUTM2 fusions and may recur rapidly, with transformation to HGESS and aggressive behavior. Our findings suggest that at least a subset of YWHAE::NUTM2 HGESS evolves from LGESS. We suggest that cyclin D1 and CD10 staining should be performed in all LGESS. Diffuse staining for cyclin D1 and/or negative or focal staining for CD10 should suggest the possibility of a YWHAE::NUTM2 fusion, and appropriate molecular testing should be undertaken. Since no single morphological or immunohistochemical parameter is entirely sensitive for fusion status, we also suggest that testing for a YWHAE::NUTM2 gene fusion should be considered in all cases of LGESS and, if a fusion is present, this should raise the possibility of subsequent high-grade transformation and aggressive behavior, even though such cases should still be categorized as LGESS. Although seemingly rare, ESN and LGESS with YWHAE::NUTM2 fusions may be under-recognized due to a lack of routine fusion testing.

[Endometrial stromal sarcoma: French Guidelines from the French Sarcoma Group and the Rare Malignant Gynecologic Tumors Group]. / Sarcomes du stroma endométrial de bas grade : référentiels de prise en charge du GSF-GETO/NETSARC+ et du groupe TMRG.

Low-grade endometrial stromal sarcoma (LG-ESS) accounts for approximately 15% of all uterine sarcomas. Median age of patients is around 50 years and half of the patients are premenopausal. In all, 60% of cases present with FIGO stage I disease. Preoperatively radiologic findings of ESS are not specific. Pathological diagnosis remains essential. This review aimed to present the French guidelines for low grade ESS treatment within the Groupe sarcome français - Groupe d'étude des tumeurs osseuse (GSF-GETO)/NETSARC+ and tumeur maligne rare gynécologique (TMRG) networks. Treatments should be validated in multidisciplinary team involved in sarcomas or rare gynecologic tumors. Hysterectomy is the cornerstone of treatment for localized ESS, and morcellation should be avoided. Systematic lymphadenectomy in ESS does not improve the outcome and is not recommended. Leaving the ovaries in situ in stage I tumors could be discussed for young women. Adjuvant hormonal treatment could be considered, for two years for stage I with morcellation or stage II and livelong for stages III or IV. Nevertheless, several questions remain, such as optimal doses, regimens (progestins or aromatase inhibitors) and duration of therapy. Tamoxifen is contraindicated. Secondary cytoreductive surgery if feasible for recurrent disease, appears to be an acceptable approach. Systemic treatment for recurrent or metastatic disease is mainly hormonal, with or without surgery.

Primary ovarian endometrial stromal sarcoma after hysterectomy associated with multiple organ invasion: A case report.

RATIONALE: Endometrial stromal sarcoma (ESS) is a rare disease in patients with uterine malignancies, accounting for <1%. Low-grade endometrial stromal sarcoma (LGESS) accounts merely 0.2% of gynecologic malignant tumor. Primary low-grade extrauterine endometrioid stromal sarcomas (LGEESS) is even more uncommon, with only a few documented case reports. We report a case of primary LGEESS exhibiting widely invasion in multiple organs after hysterectomy, which is the first case reported in Jiangsu Province of China. PATIENT CONCERNS: A 42-year-old nulliparous female with dysgnosia presented with a moderate amount of irregular vaginal bleeding, abdominal pain and distension, and frequent urination for 2 days. Her surgical history included a total hysterectomy and bilateral salpingectomy for uterine fibroids 6 years ago. Ultrasonography and the abdominal and pelvic computed tomography scan detected some solid polycystic masses in the pelvic and abdominal cavities. DIAGNOSES: The histopathology of the specimen confirmed the diagnosis of LESS in the absence of florid endometriosis. The patient was diagnosed with primary extrauterine endometrial stromal sarcoma at FIGO stage III. INTERVENTIONS: Surgery and histopathology were performed. OUTCOME: After surgery, the patient was maintained on leuprorelin acetate microspheres with sustained release for injection at 3.75 mg once every 4 weeks while refusing further radiotherapy. LESSONS: The diagnosis of primary LGEESS is challenging mainly because of their unforeseen location and nongynecologic signs and symptoms. Total hysterectomy and bilateral salpingo-oophorectomy are recommended to LGESS, while additional resection for extrauterine disease depends on disease extent and resectability.

High-Grade Endometrial Stromal Sarcomas With YWHAE::NUTM2 Gene Fusion Exhibit Recurrent CDKN2A Alterations and Absence of p16 Staining is a Poor Prognostic Marker.

High-grade endometrial stromal sarcomas (HGESSs) are aggressive uterine tumors harboring oncogenic fusion proteins. We performed a molecular study of 36 HGESSs with YWHAE::NUTM2 gene fusion, assessing co-occurring genetic events, and showed that these tumors frequently harbor recurrent events involving the CDKN2A locus on chromosome 9p. Using array-based copy number profiling and CDKN2A fluorescence in situ hybridization, we identified homozygous and hemizygous deletions of CDKN2A in 18% and 14% of tumors (n = 22 analyzed), respectively. While all YWHAE-rearranged HGESSs with retained disomy for CDKN2A were immunohistochemically positive for p16INK4 (p16), all tumors with homozygous deletion of CDKN2A showed complete absence of p16 staining. Of the 2 tumors with a hemizygous deletion of CDKN2A, 1 showed diffuse and strong p16 positivity, whereas the other showed complete absence of staining. In the p16-negative case, we did not find intragenic mutations or DNA promoter methylation to explain the p16 protein loss, implicating other mechanisms in the regulation of protein expression. In our cohort, subclonal or complete absence of p16 staining was associated with worse overall survival compared with positive p16 staining (1-year overall survival: 28.6% vs 90.7%, respectively; n = 32; P < .001), with all 7 patients in the p16-negative group having succumbed to their disease within 2 years of diagnosis. Our results suggested CDKN2A alterations as a cooperative driver of tumorigenesis in a subset of HGESSs with the YWHAE::NUTM2 gene fusion and showed p16 to be a potential prognostic marker.

Expanding the molecular spectrum of gene fusions in endometrial stromal sarcoma: Novel subunits of the chromatin remodeling complexes PRC2 and NuA4/TIP60 as alternative fusion partners.

Endometrial stromal sarcomas (ESS) are morphologically and molecularly heterogeneous. We report novel gene fusions (EPC1::EED, EPC1::EZH2, ING3::PHF1) identified by targeted RNA sequencing in five cases. The ING3::PHF1-fusion positive ESS presented in a 58-year-old female as extrauterine mesocolonic, ovarian masses, and displayed large, monomorphic ovoid-to-epithelioid cells arranged in solid sheets. The patient remained alive with disease 13 months after surgery. The three ESS with EPC1::EED occurred in the uterine corpus in patients with a median age of 58 years (range 27-62 years). One tumor showed a uniform epithelioid nested morphology, while the other two were composed of monomorphic spindle cells in fascicles with elevated mitotic figures, focal tumor cell necrosis, and lymphovascular invasion. At a median follow-up of 20 months, two patients developed local recurrence, including one with concomitant distant metastasis, while one patient remained free of disease. All three patients were alive at the last follow-up. The EPC1::EZH2-fusion positive ESS presented in a 52-year-old female in the uterus, and displayed uniform spindled cells arranged in short fascicles, with focally elevated mitotic activity but without necrosis. The patient remained free of disease 3 months after surgery. All cases were diffusely positive for CD10; four diffusely express estrogen and progesterone receptors. Our study expands the molecular spectrum of EPC1 and PHF1-related gene fusions in ESS to include additional novel subunits of the PRC2 and/or NuA4/TIP60 complexes. These cases displayed a monomorphic epithelioid or spindled phenotype, spanning low-grade and high-grade cytomorphology, all expressing CD10 and commonly ER and PR, and are prone to local and/or distant spread.