Parathyroid Hormone-Related Protein-Producing Adenocarcinoma Suspicious of Lung Cancer: A Case Report

Introduction: Lung adenocarcinoma with parathyroid hormone (PTH)-related hypercalcemia is uncommon.

Case presentation: A 69-year-old man was admitted to our hospital due to anorexia and fatigue. Serum calcium (15.0 mg/dL) and carcinoembryonic antigen (361.7 ng/mL) were extremely high, and PTH-related protein (PTH-rP) also elevated (16.7 pmol/L). Systemic computed tomography revealed multiple enlarged lymph nodes and disseminated peritoneal nodules, with irregularly shaped nodules in the upper lobe in the left lung. Ultrasound-guided biopsy from the axillary lymph node revealed adenocarcinoma. Immunohistological staining showed the tumor cells to be positive for cytokeratin 7 and PTH-rP and negative for cytokeratin 20 and thyroid transcription factor-1. Although the primary origin remains undetermined despite detailed examinations, possible primary tumor was considered to be lung adenocarcinoma in the present case. The serum calcium level was reduced by denosumab, but the patient died 20 days after admission.

Conclusion: The present case demonstrated the importance of considering oncological emergency, such as hypercalcemia and/or PTH-rP-producing hypercalcemia, in patients with adenocarcinoma.