A case of discrepant laboratory results in samples obtained from a central venous catheter and peripheral veins: when solving a pre-analytical mystery could improve patient care.

It is now generally accepted that laboratory errors or inaccurate results are mainly due to deficiencies in the pre-analytical phase. In this report, we describe the case of a 64-year-old male affected by a relapsing follicular lymphoma, who has been treated with chemotherapy through a central venous catheter (CVC). Four different samples were collected alternatively through peripheral venipuncture and CVC sampling. Unexpectedly, the samples collected from the two different sources showed contrasting results, with the presence of unusual macrophage-like cells in the samples obtained from CVC. It was later found that the CVC was displaced into the pleural space. This case report shows how the sampling process can sometimes influence test results and how it can help clinicians identify clinical conditions that have not yet manifested.