Chronic lymphoproliferative disorders (CLPDs) are a fascinating group of diseases that provide us the opportunity to study the disease characteristics over a longer period (as a result of better life expectancy) in many patients without a pressing need of therapy. They are a heterogeneous group of diseases requiring targeted and specific therapeutic approaches. They could be of both B- and T-cell origin. Of these, chronic lymphocytic leukemia (CLL) comprises 90%, being the most common CLPD worldwide. The incidence of CLL is reported to be low in Asia, especially India, China and Japan. Hairy cell leukemia (HCL) and prolymphocytic leukemia (PLL) are uncommon types of CLPDs the world over. Other rarer varieties of CLPDs include leukemic phases of lymphomas like mantle cell lymphoma (MCL), follicular lymphoma (FL), splenic lymphoma with villous lymphocytes (SLVL) and even more uncommon are T-cell CLPDs. Prognostic parameters are applicable only in the context of correct diagnosis. Therefore it is important to make the correct diagnosis of the disease under evaluation.
Over the last few years, the ability of hematologists to diagnose CLPD more accurately has vastly improved with the help of multiple diagnostic modalities, including cell morphology, histopathology of affected tissue, immunologic markers and molecular and cytogenetic investigations. As in acute leukemias, flow cytometric immunophenotyping (FCM-IPT) has proved to be useful for the characterization and classification of CLPDs. FCM-IP has emerged as an excellent diagnostic technique for assigining lineage and stage of differentiation and maturation.
CLL being the most common, comprised 90% of CLPDs. CLL is the most common leukemia (40%) encountered in the Western population. But the incidence of CLL is reported to be lower in Asia, especially in India, China and Japan. While the proportion of CLPDs was 30.23% of all hematologic neoplasms analyzed during the study period of two years, the proportion in the West has varied between 39 and 52%. A better understanding of the biology of CLL has emerged in the past decade, which has resulted in the availability and adoption of many newer prognostic markers in addition to the conventional parameters [e.g. Rai and Binet staging systems, bone marrow (BM) infiltration patterns, FCM markers, serum lactate dehydrogenase (LDH) levels and lymphocyte doubling time (LDT)]. Prognostic parameters are relevant only in the context of correct diagnosis.
Multiparameter FCM-IPT has become a powerful tool for ascertaining the ontogeny in CLPDs by virtue of its high throughput, low turnaround time and feasible logistics. The FCM technique is gaining acceptance in many clinical laboratories in India. Guidelines for IPT of hematolymphoid neoplasms by FCM have been formulated recently. However, the data about the FCM use for CLPD in Indian setting is lacking. This study may hence prove as baseline and further multi-centric studies are required to delineate the characteristics and biological behavior of these diseases in the Indian context.
The FCM results should be interpreted in the context of clinico-laboratory data and morphological features with a wide panel of markers instead of a single marker. Prognostic parameters are applicable only in the context of correct diagnosis. Therefore it is important to make the correct diagnosis of the disease under evaluation because the disease course and treatment of individual CLPD is dependent on the subtype of CLPD. However, even within each subtype, the clinical presentation, morphologic appearance and response to therapy is heterogeneous.