Paraneoplastic Pulmonary Embolism Revealing Metastatic Uterine Carcinosarcoma

Background Venous thromboembolism (VTE) can be a paraneoplastic phenomenon and may occasionally be the first manifestation of an occult malignancy. We present the case of an elderly woman whose “unprovoked” pulmonary embolism (PE) led to the diagnosis of metastatic uterine carcinosarcoma, an aggressive endometrial cancer subtype. Case A 74‐year‐old postmenopausal woman with a history of uterine fibroids and prior breast ductal carcinoma in situ developed progressive dyspnea. She was found to have bilateral PEs with right heart strain and extensive bilateral deep vein thromboses (DVTs). Imaging also revealed ascites, widespread lymphadenopathy, and an 8‐cm uterine mass. Tumor marker evaluation showed a markedly elevated CA‐125 level. Diagnostic procedures including endometrial biopsy, ascitic fluid cytology, and lymph node biopsy confirmed Stage IVB uterine carcinosarcoma. She was managed with anticoagulation for VTE and initiated on systemic chemotherapy (carboplatin plus paclitaxel), given that surgical cure was not feasible due to metastases. Outcome After treatment initiation, the patient′s respiratory status improved, and she was discharged on long‐term anticoagulation and chemotherapy, with plans for outpatient oncology follow‐up. Conclusion This case highlights that an unexplained (unprovoked) PE in an older adult can be the harbinger of an underlying malignancy. In women, especially those with additional red flags such as abdominal distension or abnormal uterine bleeding, prompt evaluation for gynecologic cancers is warranted. Early identification of the occult cancer allowed appropriate therapy; however, uterine carcinosarcoma carries a poor prognosis once metastatic. Clinicians should maintain a high index of suspicion for hidden malignancy in cases of idiopathic VTE, as timely diagnosis can guide life‐saving interventions.