Paraneoplastic leukemoid reaction: Case report and review of the literature

We recently encountered a patient with unexplained hyperleukocytosis (105.4 K/μL at presentation), subsequently found to have colon cancer with a marked tumor-associated neutrophilic infiltrate; the leukocytosis abruptly improved after tumor removal. Paraneoplastic leukemoid reaction (PLR) is a rare entity, occurring due to tumor cytokine secretion (typically granulocyte-colony stimulating factor [G-CSF]). We describe a case and aggregate results of previously published cases.

We reviewed the English-language literature for all prior reports of PLR, recording age, gender, histologic diagnosis, WBC count, G-CSF level, and overall survival. We analyzed clinicopathologic variables' impact on survival.

We identified 179 cases (mean age 64; 72 % M). Adeno-, squamous cell, sarcomatoid, and undifferentiated carcinomas accounted for >70 %. Esophagus, gallbladder, lung, liver, and pancreas were the most common primaries. At time of publication 81 % of patients had died, with mean overall survival of 4 months. There was no correlation between WBC count and G-CSF level. On univariate analysis, WBC count was the only variable associated with survival (P = 0.03). Patients with WBC counts >100 K/μL were twice as likely to die as those with counts from 11 K to 40 K/μL.

PLR, typically carcinoma-associated, is characterized by dismal prognosis. The WBC count is inversely related to survival. Knowledge of this phenomenon militates against protracted, expensive work ups. In malignant neoplasms with prominent neutrophilic stroma, the pathologist should correlate with the WBC count and, if markedly elevated (>40 K/μL), raise consideration for PLR.