MBL

Meaning of MBL: MBL is a condition marked by an elevated number of identical B cells in the blood that occasionally precedes a related blood cancer.

Definition of MBL

MBL, short for monoclonal B-cell lymphocytosis, is a condition in which a higher than normal number of B cells, a type of white blood cell, are found circulating in the blood, and these B cells are monoclonal, meaning they are all identical copies descended from a single original cell. The condition is generally identified incidentally through routine blood testing performed for another reason, since it typically causes no symptoms on its own.

MBL is considered a precursor condition rather than a cancer itself, though people with MBL have a modestly increased likelihood of eventually developing a related B cell cancer, most often chronic lymphocytic leukemia. Not everyone with MBL goes on to develop this or any other related condition.

Because MBL by itself generally does not require treatment, it is typically monitored over time with periodic blood testing, an approach aimed at identifying whether the B cell count or pattern changes in a way that might indicate progression toward a related blood cancer.