Paraneoplastic leukemoid reaction in solid tumors

Leukemoid reaction is defined as leucocytosis >50,000/μL. When it occurs in association with a malignancy, and infection or leukemia has been ruled out, it is termed as paraneoplastic leukemoid reaction. A patient presented with fatigue, generalized weakness, and abdominal distension and was incidentally noted to have a white blood cell count of 139,000/μL. Leukemia was ruled out by peripheral smear and flow cytometry. Computed tomography-guided biopsy of thickened omentum revealed poorly differentiated metastatic carcinoma. He died 3 days after admission with a peak white blood cell count of 180,000/μL. Previous reports and pathophysiology of paraneoplastic leukemoid reaction are reviewed.