Case presentation

A 53-year-old woman with no pertinent medical history presented with several weeks of progressive abdominal distension, exertional dyspnea, reduced oral intake, and decreased urine output. She denied prior malignancy, recent chemotherapy exposure, or use of nephrotoxic medications.

Physical examination revealed a markedly distended abdomen with tense ascites and preserved bowel sounds. No signs of peritonitis were present. Initial laboratory evaluation on admission (hospital day 1) demonstrated acute kidney injury with a serum creatinine level of 4.09 mg/dL, along with hyperuricemia (uric acid 12 mg/dL), hyperkalemia (potassium 6.1 mEq/L), hyperphosphatemia (phosphorus 8.7 mg/dL), and hypocalcemia (calcium 6.9 mg/dL), fulfilling all four Cairo-Bishop laboratory criteria for TLS (Table 1). Lactate dehydrogenase was 310 U/L. Renal ultrasonography demonstrated preserved renal size and architecture without hydronephrosis. Computed tomography (CT) of the abdomen and pelvis revealed massive ascites and a large pelvic mass measuring 16.2 × 15 × 15 cm, without evidence of urinary tract obstruction (Figure 1).

Parameter | Day 1 (admission) | Day 5 (posttreatment) | Cairo-Bishop threshold
Creatinine (mg/dL) | 4.09 | 0.89 | >1.5 × ULN
Uric acid (mg/dL) | 12 | 2.6 | ≥8
Potassium (mEq/L) | 6.1 | 4.2 | ≥6.0
Phosphorus (mg/dL) | 8.7 | 3.3 | ≥4.5
Calcium (mg/dL) | 6.9 | 8.3 | ≤7.0
LDH (U/L) | 310 | - | -

Figure 1: Contrast-enhanced CT of the abdomen and pelvis (coronal view), demonstrating a large heterogeneous pelvic mass measuring approximately 16.2 × 15 × 15 cm, with massive ascitesCT: computed tomography

Diagnostic paracentesis was performed on the day of admission, and cytologic examination of the ascitic fluid demonstrated metastatic carcinoma. Immunoperoxidase stains performed on cell block preparations, with reactive controls, showed the neoplastic cells to be positive for CK AE1/3, CK7, and p16 (strong cytoplasmic staining), and negative for CK20, GATA-binding factor 3, estrogen receptor (0%), and progesterone receptor (0%) (Figure 2). This immunoprofile argued against urothelial, breast, and colorectal primaries; PAX8 and WT1 were not performed on this specimen.

Figure 2: Ascitic fluid cytology demonstrating metastatic carcinoma consistent with an epithelial malignancyAscitic fluid cell block preparation demonstrating clusters of atypical epithelial cells consistent with metastatic carcinoma. Immunoperoxidase stains performed on cell block preparations, with reactive controls, were positive for CK AE1/3, CK7, and p16 (strong cytoplasmic staining), and negative for CK20, GATA-3, estrogen receptor, and progesterone receptor (a profile arguing against urothelial, breast, and colorectal primaries)GATA-3: GATA-binding factor 3

Tumor marker evaluation revealed elevated cancer antigen (CA)-125 at 445 U/mL and carcinoembryonic antigen (CEA) at 3.66 ng/mL, yielding a CA-125:CEA ratio of 121.6, strongly suggesting a gynecologic primary malignancy.

Given the absence of recent chemotherapy, radiation therapy, or other identifiable triggers, spontaneous TLS secondary to advanced ovarian carcinoma was diagnosed based on the combination of imaging, immunophenotype, and tumor marker profile. The patient received aggressive intravenous hydration, rasburicase (initiated on hospital day 1), electrolyte correction, and close multidisciplinary monitoring. Renal replacement therapy was not required. Metabolic abnormalities progressively resolved, and renal function recovered, with serum creatinine normalizing to 0.89 mg/dL by hospital day 5.

Following stabilization, the patient was evaluated by gynecologic oncology and, on hospital day 8, initiated neoadjuvant chemotherapy with carboplatin and paclitaxel. After demonstrating a favorable clinical and radiographic response, she underwent interval cytoreductive surgery approximately five months later, consisting of total abdominal hysterectomy, bilateral salpingo-oophorectomy, omentectomy, and resection of residual disease.

Histopathologic examination of the surgical specimen revealed extensive treatment-related changes characterized by ovarian necrosis, hemorrhage, hemosiderin deposition, chronic inflammation, and multinucleated giant cell reaction (Figure 3).

Figure 3: Histopathologic examination of the resected ovarian specimen (H&E stain, 40× magnification; image provided by HRP Laboratory), demonstrating extensive treatment-related changes, including chronic inflammation, stromal degeneration, and multinucleated giant cell reaction. No residual invasive carcinoma was identified, findings consistent with a complete pathologic response following neoadjuvant carboplatin-paclitaxel chemotherapyH&E: hematoxylin and eosin; HRP: Hato Rey Pathology

No residual invasive carcinoma was identified in the ovarian, omental, mesenteric, pelvic ligament, or peritoneal biopsies. These findings were consistent with an essentially complete pathologic response following neoadjuvant carboplatin-paclitaxel chemotherapy.

Subsequent surveillance demonstrated normalization of CA-125 to 5.2 U/mL. Follow-up positron emission tomography (PET)/CT imaging revealed complete resolution of the previously identified pelvic mass and no evidence of fluorodeoxyglucose-avid residual or metastatic disease (Figure 4).

Figure 4: Follow-up FDG PET/CT demonstrating complete metabolic response(A) Coronal CT, bone window. (B) Coronal PET (whole-body MIP), anterior projection. (C) Coronal fused PET/CT. (D) Axial fused PET/CT at the level of the previously identified pelvic mass, showing physiologic renal radiotracer excretion with no abnormal FDG uptake. (E) Coronal PET (whole-body MIP), posterior projection. (F) Sagittal CT, bone window. (G) Sagittal PET. (H) Sagittal fused PET/CT. (I) Axial PET at the same level, showing physiologic renal radiotracer excretion. (J) Axial CT, soft-tissue window, at the same level. (K) 3D volume-rendered bone reconstructionFollow-up PET/CT performed in March 2026, demonstrating complete resolution of the previously identified pelvic mass with no evidence of FDG-avid residual or metastatic diseaseCT: computed tomography; PET: positron emission tomography; MIP: maximum intensity projection; FDG: fluorodeoxyglucose; 3D: three-dimensional

At her most recent follow-up visit, the patient remained in complete clinical and radiographic remission without evidence of disease recurrence, while continuing maintenance therapy with bevacizumab biosimilars (Mvasi (bevacizumab-awwb) and Zirabev (bevacizumab-bvzr), per the institutional formulary).