Paraneoplastic β-hCG secretion in a postmenopausal woman with sarcoma, endometrial carcinoma, and metastatic lung disease: a case report and review of the literature.

BACKGROUND: Human chorionic gonadotropin (hCG) is a well-known diagnostic and prognostic marker for gestational trophoblastic neoplasm (GTN). Ectopic β-hCG production in sarcomas is rare, and its role in the pathogenesis and clinical outcomes in sarcoma has not been established. This case highlights the diagnostic challenge posed by markedly elevated serum β-hCG levels in a patient with concurrent sarcoma and endometrial carcinoma. CASE PRESENTATION: A 60-year-old postmenopausal woman presented to the orthopedic department with complaints of progressive pain and discomfort in her left upper limb. Over the past nine months, she underwent two separate open reduction and internal fixation procedures for left humeral fractures following two separate incidents of minor trauma. Imaging studies revealed an osteolytic lesion in the humerus, a hypermetabolic lung nodule, and an intrauterine mass. Her serum β-hCG level was significantly elevated at 127,306 mIU/mL. Subsequent pathological analysis confirmed the diagnosis of undifferentiated sarcoma with lung involvement and concurrent endometrial cancer and ruled out the possibility of choriocarcinoma. Serum β-hCG monitoring showed a strong correlation between the variation and clinical course of the sarcoma, decreasing after tumor resection and increasing with disease progression and metastasis. A key analytical complexity was the consistent negative β-hCG staining on immunohistochemistry (IHC) across all tumor tissues (humerus, lung metastasis, and endometrium). CONCLUSION: A markedly elevated β-hCG level in a non-pregnant patient should not be automatically attributed to gynecological cancers. Undifferentiated sarcoma can be a rare source of massive ectopic β-hCG production, even with negative IHC staining.