Leukemoid reaction in a patient with adenocarcinoma of the lung: a case report.

Introduction: Lung cancers are characterized by high incidence, prevalence and mortality. They may be associated with numerous paraneoplastic syndromes. Mild leukocytosis is not rare. The case described here, however, is of a female patient with adenocarcinoma of the lung who developed extreme leukocytosis at over 140,000 cells/μL. Descriptions of such leukemic forms of lung cancer are few and far between in the literature. In our case, the complete hematological diagnostic investigation, which included cytological, immunocytological, cytogenetic, histological and molecular genetic tests of the bone marrow (mutation analyses of BCR-ABL and JAK2), was accompanied for the first time by a molecular genetic workup of the primary tumor for epidermal growth factor receptor and K-RAS gene mutations.

Case Presentation: We present the medical case of a 51-year-old female Caucasian patient, who was diagnosed with a poorly differentiated stage IV (International Union Against Cancer staging) adenocarcinoma of the lung. While undergoing treatment, our patient developed extreme leukocytosis, for which, despite extensive diagnostic tests, no infection-related or hematological cause could be identified. The tumor proved to be highly resistant to treatment. Our patient died only five months after the initial diagnosis.

Conclusion: A leukemoid course can most likely be interpreted as the paraneoplastic production of hematopoietic growth factors. Despite the absence of a verified primary hematological origin, this possibility should always be investigated in all patients in a comparable situation.