SMARCA4-deficient undifferentiated uterine sarcoma: A Case Report and Literature Review

Abstract

SMARCA4-deficient undifferentiated uterine sarcoma (SDUS) is a highly invasive single-gene malignant tumour caused by mutations in the SMARCA4 gene. SDUS has a poor prognosis and has no established treatment scheme at present. What's more, there is no relevant research on the role of immune microenvironment analysis in SDUS worldwide. Here, we report a case of SDUS that combined examinations via morphology, immunohistochemistry, and molecular detection and analysed the immune microenvironment. Therefore, our report will help in the diagnostic awareness of SDUS.

1. Introduction

Uterine sarcomas account for 3–5% of all uterus tumours with an incidence rate of 1.55–1.95 per 100,000 women per year¹. The inactivation mutation of the SMARCA4 gene in this sarcoma was first discovered and proposed by Kolin et al. in 2018².SDUS takes SMARCA4 as the main driving gene and shares a similar morphology along with a low tumor mutation burden³. SMARCA4 is involved in many cellular processes, such as transcriptional regulation, DNA damage repair, and is usually found in the promoters of transcriptional genes. As such, the changes in the transcriptional and epigenetic regulations caused by SMARCA4 loss may play a central role in driving tumorigenesis⁴. We report a case of sarcoma showing SDUS and review the literature.

At present, there are less than 30 cases of SDUS worldwide. The average age of patients is 36 years, which is much younger than that of patients with undifferentiated endometrial cancer (average 61 years)¹, but slightly older than that of patients with small cell carcinoma of the ovary, hypercalcaemic type (SCCOHT) (average 29 years)⁵. Since SDUS is highly invasive and has no established treatment scheme at present, despite active surgical interventions, the prognosis is extremely poor with a median survival time of only 9 months⁶. Currently, the diagnosis of SDUS is mainly based on morphology, loss of BRG1, and SMARCA4 gene deletion. Morphologically, SDUS is composed of atypical, epithelioid cells with prominent rhabdoid morphology, which is sometimes difficult to distinguish from the SCCOHT⁷. Altogether, accurate early diagnosis and the immune microenvironment analysis in SDUS have great significance for the prognosis of patients.

2. Case Report

A 27-year-old Chinese woman presented with menstrual volume increase for three years and vaginal bleeding for 24 days. Enhanced arterial phase CT showed that the volume of the uterus significantly increased, and space-occupying lesions could be seen in the uterus with a size of about 9.5 cm × 8.5 cm × 8 cm. A mass with a mixed density shadow was observed in the uterus, and the boundary was unclear (Fig. 1-A). The size of the uterus was 12 cm × 10 cm ×9 cm, the depth of the uterine cavity was 8 cm, and the thickness of the endometrium was 0.2–0.3 cm. There was a large mass in the uterine cavity at a size of 9 cm × 8 cm × 8 cm; the section was grey white and grey red. The bilateral ovaries and oviduct were not involved by SDUS in Enhanced arterial phase CT and surgery (Fig. 1-B).

During surgery, diffuse uterus enlargement was identified, about the size of 16 weeks of gestation; the surface of the uterus had a hard texture with many hard nodules, each with a diameter of about 1 cm. When a cut was made into the uterine cavity, the lesion had no boundary with the normal myometrium and were easily broken. The adhesion between the left bladder and the lower uterine segment was dense, and the tumour had infiltrated into the serosal surface in the lower-left anterior wall of the uterus. No lesions were found in bilateral appendages or other organs.

Haematoxylin and eosin staining was performed. Microscopically, the tumour cells were diffusely distributed, displaying flake or acinar shapes. SDUS tumour cells in some areas had lost adhesion, and some SDUS tumour tissues grew around and invaded the blood vessels (Fig. 2-A). Extensive necrosis was observed (Fig. 2-B). Vascular and normal endometrial gland invasion was observed (Fig. 2-C). The tumour cells were epithelioid and had eosinophilic cytoplasm, and some cells showed nuclear deviation towards the cytoplasm. These cells were rhabdoid with round or oval nuclei (Fig. 2-D). The results of immunohistochemistry of the Ki-67 proliferation marker showed a high percentage (60%) of cell staining, with the expression of INI-1, the local expression of CD10, and the lack of expression of BRG1, CK (Pan), SYN, Desmin, and ER (Fig. 2).

The NGS was conducted at Geneseeq Technology Inc. (Nanjing, China). Formalin-fixed paraffin-embedded sections of the uterine tumour were subjected to comprehensive NGS analysis with 425 predefined related genes. Data were sequentially analysed by an effective bioinformatics process. Germline mutations were filtered out by comparing to patient’s whole blood controls. In our case, the genetic analysis result showed that no germline mutation was detected in her family. A SMARCA4 splicing mutation, c.355 + 190_616del, was detected at a MAF of 86.4% in the tumour sample, accompanied by a SMARCA4 frameshift mutation p.H571Gfs (45.8%). TMB: 1.1 mutations/MB (Fig. 3). Our NGS test includes MMR, MSI, PTEN, PIK3CA, TP53, beta-catenin, etc. Our NGS test report showed SMARCB1, CTNNBI, MMR, MSI, PTEN, PIK3CA, TP53 were negative. In conclusion, a clinical diagnosis of SDUS was confirmed by expert consultation.

The Multiple Immunofluorescent Staining was conducted at Genecast Biotechnology Co. Ltd. (Beijing, China). Briefly, 4-µm thick sections were cut from SDUS tissues for analysis. Primary antibodies for PD-L1(1:25), CD68 (1:500), PD-1 (1:50) were incubated for 1 h at 25℃, and CD8 antibody (1:100) was incubated overnight at 4℃. The results showed that there were some infiltrating immune cells expressing CD8(+,0.92%) and CD68(+,0.2%) in SDUS tissues. A few cells expressing PD-1(+,0.06%) and PD-L1(+,0.06%) were detected by immunofluorescence (Fig. 4). The results showed that some of the immune cells expressing CD3 and CD8 had infiltrated into SDUS tissues, but no PD-L1 expression was detected (Fig. 4). Approximately 27 T-cells per high power field (HPF) had infiltrated into SDUS tissues. The results showed that SDUS had immunogenicity. The antibody information is shown in Table 1.

In our case, the tumour stage was pt3bnxmx. the patient underwent hysterectomy and bilateral salpingo-oophorectomy, then received gemcitabine and docetaxel chemotherapy for 4 cycles. After positron emission tomography, computed tomography (PET-CT) examination, it was found that there were hypermetabolic signals in the left iliac fossa and pelvic cavity of the patient, suggesting that the tumour had a trend of further deterioration (Fig. 5). The treatment plan was changed to epirubicin and ifosfamide chemotherapy. During 3 cycles of treatment, the patient eventually gave up on chemotherapy due to severe side effects. The patient is still alive and displayed the left iliac fossa lesion enlargement in the 6-month follow-up check.

3. Discussion

There are currently less than 30 SDUS cases published worldwide¹. Although active surgical treatment is performed, the prognosis is poor. Because of the rarity and specificity of SDUS, there is no established treatment at present. Therefore, accurate diagnosis is of great significance for the prognosis of patients. Pathologists especially need to differentiate SDUS from the following types of similar tumours.

SCCOHT is usually a single huge, unilateral mass (average 15 cm), while SDUS may involve the bilateral adnexa⁸. There are also differences in clinical manifestations due to different tumour origins: SDUS often presents with cervical mass or vaginal bleeding, while SCCOHT most commonly manifests as abdominal pain or as an abdominal mass, with less cervical mass or vaginal bleeding⁸. Histologically, epithelioid uterine leiomyosarcomas show obvious nuclear pleomorphism, but SDUS cells have more consistent atypia without obvious pleomorphism. Immunohistochemically, the detection of BRG1 deletion can effectively exclude leiomyosarcoma⁹. At the molecular level, leiomyosarcoma often has no SMARCA4 deletion mutation. Endometrial stromal sarcomas cells usually do not have rhabdoid morphology. Immunohistochemistry shows that CD10 is strongly expressed. CyclinD1 strongly expressed is found in high-grade stromal sarcoma. These markers are not found in SDUS. At the molecular level, endometrial stromal sarcomas often have no SMARCA4 deletion mutation. No mutations associated with endometrial mesenchymal sarcoma were found in our NGS test. As for distinguishing SDUS from undifferentiated endometrial carcinoma, SDUS often has a lobulated structure¹⁰, fewer TP53 mutations, and is characterized by inactivation mutations in SMARCA4¹⁰. SDUS often presents in normal endometrial glands, and SDUS is microsatellite-stable and shows a low expression of Claudin-4 / CK / EMA, which are unlike undifferentiated endometrial carcinomas. The average age of patients with SDUS is 36 years, which was younger than that of patients with undifferentiated endometrial cancer⁶. Both proximal epithelioid sarcomas and SDUS have similar onset ages, but there are still differences. First, SDUS occurs in the uterus, and proximal epithelioid sarcomas are usually located in the groin or vulva. Secondly, immunohistochemistry shows that CD34 is expressed in more than 50% of epithelioid sarcomas, but we have found a lack of CD34 expression in SDUS². Next, the typical feature of epithelioid sarcoma is SMARCB1 deletion, but SMARCA4 deletion mutation is only found in SDUS².

Currently, targeted drug development for SCCOHT has focused on several approaches^11–12, and studies have shown that immunotherapy seems to be the best choice for treatment⁴. Following the accepted knowledge that SCCOHT demonstrated a good response to immunotherapy¹³. As SCCOHT and SDUS have high similarities in morphology and gene mutations and are both low mutation load tumors, future SDUS treatments may take direction from current SCCOHT treatments. At present, there is no established treatment and there is no relevant research on the role of immune microenvironment analysis in SDUS. Based on this, we examined the expression of CD3, CD8, PD-1, and PD-L1 in SDUS tumour cells and further explored the tumour immune microenvironments. Our immunoassay results showed that approximately 27 CD8+/CD3 + T-cells per high power field (HPF) had infiltrated into SDUS tissues. The results showed that SDUS had immunogenicity.

Our study has some limitations. Firstly, the patient eventually gave up on clinical treatment due to severe side effects in chemotherapy, which limits our ability to conduct further clinical trials. In the future, we hope to find more SDUS cases for the study of the immune microenvironment. Second, no germline mutation was detected in her family. Identification of cases of malignant tumours with a SMARCA4 deletion mutation in the uterus is important; investigations of the immune microenvironment from various angles in SDUS are needed.

4. Conclusion

SDUS poses a diagnostic challenge as little data concerning their histology, long-term follow-up and outcome are available. Further clinicopathological and molecular cytogenetic studies of more cases are necessary to further characterize SDUS.

Declarations

Informed consent 

A signed informed consent was obtained for this case report.

Funding

There is no financial support 

Declaration of Competing Interest 

The authors declare that they have no conflict of interest in this case report.

Author Contributions

The first author (RR, F) wrote and edited the final manuscript. The co-first author (J, G) performed the lab work. The second (DH, C), third (JL, H), fourth authors (HL, C) provided the case clinical information. The corresponding author (MZ, L) guides the manuscript writing.

Acknowledgments

We would like to thank the Department of Pathology of Xiamen Humanity Hospital and Xiang’an Hospital of Xiamen University, Genecast Biotechnology Co. Ltd.

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