A 53-year-old Chinese female presented to the Emergency Department of our hospital for persistent abdominal pain and distension for over two months. Two months ago, the patient went to a local hospital and obtained a transvaginal ultrasound that revealed thickened bilateral fallopian, suggesting adnexitis. She was treated with antibiotics, but the pain persisted. The serum CA125 and CA724 levels were elevated (469U/ml and 33.4U/ml, respectively). Abdomen and pelvis computed tomography (CT) showed heterogeneous stomach and bilateral adnexal masses, suggesting adnexal lesions or the Krukenberg tumor. She was then referred to the emergency room of our hospital.
In our hospital, she received thorough examinations. A gynecological examination revealed an abdominopelvic mass with an unclear boundary. The transvaginal ultrasound showed a 3.9x2.3cm solid pelvic mass with ascites (  Figure 1A  ;  Supplemental Figures S1A, B  ). The abdominal and pelvic enhanced CT, the pelvic magnetic resonance imaging (MRI), and the positron emission computed tomography (PET-CT) all revealed irregular, heterogeneous, and plump bilateral adnexal masses with diffusely thickened peritoneum, omentum, and mesangium, multiple soft-tissue nodules, slightly thickened intestinal wall, abdominal and pelvic effusion, and multiple enlarged lymph nodes (  Figures 1B-E  ;  Supplemental Figures S1C-F  ). The serum CA125 level was 439U/mL. The chest X-ray showed no abnormality. The patient underwent bilateral tubal sterilization more than 20 years ago and was found with a Helicobacter pylori infection two months ago. She went into natural menopause for one year and gave birth to two children. Personal and family history were unremarkable.
Considering the possibility of ovarian or gastrointestinal malignancies, the patient was admitted to our hospital. After admission, the patient developed aggravated abdominal distension with an increase in body temperature to 39C. After four days of intravenous anti-inflammatory, the patient underwent diagnostic laparoscopy with omentum and peritoneum biopsies in a stable condition, which suggested poorly differentiated carcinoma according to intraoperative consultation. About 2 liters of tawny ascites were drained for cytology confirmation during the operation, which revealed no tumor cells. The surgical findings showed multiple white granular tumor implants studding the omentum, peritoneum, and the surface of the diaphragm, liver, intestine, and uterus. A 9x9x3cm omental cake enclosed part of the intestine and was fixed. The omentum and intestine obscured bilateral ovaries and fallopian tubes. Combined with laboratory, imaging, and surgical findings, the possibility of advanced (stage IV) ovarian cancer was considered. Given the difficulty in performing satisfactory cytoreductive surgery, the patient was treated with three cycles of neoadjuvant chemotherapy with Paclitaxel-albumin, Carboplatin, and Bevacizumab.
After chemotherapy, the patient's serum CA125 level was reduced to 107 U/mL. Imaging examination showed reduced abdominal and pelvic effusion, while abdominopelvic lesions were roughly the same as before (  Supplemental Figure S2  ). The pathological findings of the previous operation excluded the common types of epithelial ovarian carcinoma, breast carcinoma, and neuroendocrine neoplasm. Still, the diagnosis could not be confirmed due to the poor differentiation characteristics of the tumor cells. Upper GI endoscopy and colonoscopy were performed to distinguish gastrointestinal tumors, but no mucosal lesions were identified (  Supplemental Figure S3  ). The patient further underwent cytoreductive surgery, which showed a 20x10x4cm extensive gritty nodular omental cake densely adhered to the pelvic wall and part of the intestine and mesentery (  Supplemental Figure S4A  ). The mesostenium and mesocolon were extensively thickened with contracture and stiff morphology. A heterogeneous mass about 2.5cm in diameter was found on the surface of the small intestine. The posterior wall of the uterus closely adhered to the rectum, and bilateral ovaries were enlarged with a solid nodular appearance (  Supplemental Figure S4B  ). Total hysterectomy and bilateral salpingo-oophorectomy were performed. The omentum, small intestinal mass, and left pelvic lymph nodes were also removed. All specimen was submitted for pathological confirmation. It was an unsatisfactory cytoreductive surgery (R2), with the postoperative residuals being the diffuse thickened malignancy lesions in the mesentery. The patient recovered in a stable condition without any complications and was discharged home 13 days after surgery.
Microscopic examination showed malignancy infiltration in bilateral ovaries involving the omentum, peritoneum, mass on the small intestine surface, and the serosa of the uterus and bilateral fallopian tubes. The tumor cells were uniform monotonous medium-sized round and oval with small-to-moderate eosinophilic cytoplasm, enlarged nuclei, high nuclear/cytoplasmic ratio, and uneven chromatin (  Figure 2A  ). Lymphatic vascular involvement and lymph node metastases were frequently observed (  Figure 2B  ). Solid sheets and nests of typically undifferentiated cells infiltrating surrounding normal omental tissue were present, with no abrupt keratinization (  Figure 2C  ). Comparing the two surgical specimens, there was no significant regression of tumor cells after neoadjuvant chemotherapy (  Figures 2C, D  ). Malignancy infiltration was found on the serosa of the uterus, while typical structures of the endometrium and myometrium remained, suggesting that it was not a primary uterine neoplasm (  Figure 2E  ). It is noteworthy that although the malignancies significantly infiltrated the ovary, most of the ovarian cortical and corpus albicans were intact. The lesions were mainly close to the ovarian hilus and surrounded by large blood vessels (  Figure 2F  ), so the possibility of secondary ovarian malignancy cannot be excluded.
IHC was conducted to help confirm the diagnosis (  Table 1  ). Tumor cells positively expressed monoclonal ER, INI1(SMARCB1), BRG1(SMARCA4), and ARID1a, with patchy expressions of monoclonal PR, P16, Syn, SATB2, and CK8/18. The beta-Catenin and P120 were positive in the cytoplasm. The Ki-67 labeling index was approximately 30%. There was no expression of CK pan (  Figure 2G  ), p40 (  Figure 2H  ), p63 (  Figure 2I  ), and other IHC markers (i.e., CD56, CK7, WT-1, TTF-1, Desmin, C-myc, CgA, CDX2, INSM1, SSTR2, SSTR5). Details of all the IHC results were listed in  Table 1 . Based on the morphological and IHC features, 14 malignancies with similar morphology were compared, including ovarian serous carcinoma, ovarian clear cell carcinoma, ovarian germ cell neoplasms, ovarian sex cord-stromal neoplasms, neoplasms associated with the SWI/SNF complex, colorectal carcinoma, invasive lobular carcinoma of the breast, poorly differentiated hepatic cholangiocarcinoma, low grade endometrial stromal sarcoma, high grade endometrial stromal sarcoma, rhabdomyosarcoma, malignant peripheral nerve sheath tumors, histiocytic sarcoma, and plasmacytoma (  Table 2  ). Additionally, to distinguish it from Ewing sarcoma, dual-color break-apart FISH was conducted to test for EWSR1 gene rearrangements, which revealed a negative result.
Finally, we conducted NUT immunostaining (clone C52B1) and revealed diffusely positive expression in the nucleus of tumor cells (  Figure 2J  ). However, the FISH experiment found no disruption or translocation of the NUTM1 gene locus (  Figure 2K  ). We subsequently identified the gene fusion of MXI1 exon 5 (NM_130439.3) to NUTM1 exon 3 (NM_175741.3) via a targeted RNA-based NGS platform (DA8600, Daan Gene, Guangzhou, China) on tissue samples, which finally confirmed NUT carcinoma two months after cytoreductive surgery (  Figure 2L  ). Besides, we also identified the gene fusion of MTMR3 exon 5 (NM_021090.4) to SFI1 exon 3 (NM_001007467.3).
One week after diagnosis, the patient developed fever and an increased burden of malignancy, with imaging of advanced diffusely thickened peritoneum, omentum, and mesangium, progressed multiple metastatic lymph nodes, and newly developed abdomino pelvic effusion. Unfortunately, although the patient was adequately informed and the potential feasibility of antitumor therapy was introduced, the patient refused further treatment due to financial difficulties and decided to be discharged to a local hospital for symptomatic relief and supportive treatment. She developed systemic symptoms and passed away four months and 18 days after cytoreductive surgery ( Figure 3 ).