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  TABLE 14.3: Contrasting Features of Leukaemoid Reaction and Chronic Myeloid Leukaemia.
Feature Leukaemoid Reaction CML
1. TLC 25,000-100,000/μl > 100,000/μl
2. DLC i) Dominant cells PMN’s i) All maturation stages
ii) Immature cells predominantly metamyelocytes ii) Immature cells all stages,
and myelocytes (5-15%), myeloblasts and myeloblasts and promyelocytes
promyelocytes > 5% < 10%
iii) Basophils normal iii) Basophilia present
3. NAP score Elevated Reduced
4. Philadelphia chromosome Absent Present
5. ABL-BCR fusion gene Absent Present
6. Major etiology Infections, intoxication, disseminated malignancy, RNA viruses, HTLV oncogenesis,
severe haemorrhage genetic factors, radiations, certain drugs
and chemicals
7. Additional haematologic findings i) Anaemia Anaemia
ii) Normal to raised platelet count Normal to raised platelet count
iii) Myeloid hyperplasia in bone marrow Myeloid hyperplasia in bone marrow
8. Organ infiltration Absent May be present
SECTION II
9. Massive splenomegaly Absent Present

leukaemia (AML and ALL), and chronic myeloid leukaemia and Currently, neoplasms of haematopoietic and lymphoid
chronic lymphocytic leukaemias (CML and CLL); besides there tissues are considered as a unified group and are divided
are some other uncommon variants. In general, acute into 3 broad categories:
leukaemias are characterised by predominance of I. Myeloid neoplasms: This group includes neoplasms of
undifferentiated leucocyte precursors or leukaemic blasts and myeloid cell lineage and therefore includes neoplastic
have a rapidly downhill course. Chronic leukaemias, on the proliferations of red blood cells, platelets, granulocytes and
other hand, have easily recognisable late precursor series of monocytes. There are 5 categories under myeloid series of
leucocytes circulating in large number as the predominant neoplasms: myeloproliferative disorders, myeloprolife-
leukaemic cell type and the patients tend to have more
indolent behaviour. The incidence of both acute and chronic rative/myelodysplastic diseases, myelodysplastic
leukaemias is higher in men than in women. ALL is primarily syndromes (MDS), and acute myeloid leukaemia (AML),
a disease of children and young adults, whereas AML occurs acute biphenotypic leukaemias.
at all ages. CLL tends to occur in the elderly, while CML is II. Lymphoid neoplasms: Neoplasms of lymphoid lineage
found in middle age. include leukaemias and lymphomas of B, T or NK cell origin.
Similary, over the years, lymphomas which are malignant This group thus includes B cell neoplasms (including plasma
tumours of lymphoreticular tissues have been categorised cell disorders), T cell neoplasms, NK cell neoplasms and
into two distinct clinicopathologic groups: Hodgkin’s Hodgkin’s disease.
lymphoma or Hodgkin’s disease (HD) characterised by
pathognomonic presence of Reed-Sternberg cells, and a III. Histiocytic neoplasms: This group is of interest mainly
due to neoplastic proliferations of histiocytes in Langerhans
Haematology and Lymphoreticular Tissues
heterogenous group of non-Hodgkin’s lymphomas (NHL).
In the last 50 years, several classification systems have cell histiocytisis.
been proposed for leukaemias and lymphomas—clinicians Besides the WHO classification, the FAB (French-
favouring an approach based on clinical findings while American-British) Cooperative Group classification of
pathologists have been interested in classifying them on lymphomas and leukaemias based on morphology and
morphologic features. More recent classification schemes cytochemistry is also widely used.
have been based on cytochemistry, immunophenotyping, These as well as other classification schemes have been
cytogenetics and molecular markers which have become tabulated and discussed later under separate headings of
available to pathologists and haematologists. The most recent myeloid and lymphoid malignancies.
classification scheme proposed by the World Health
Organisation (WHO) in 2002 combines all tumours of ETIOLOGY
haematopoietic and lymphoid tissues together. The basis of Like in most cancers, the exact etiology of leukaemias and
the WHO classification is the cell type of the neoplasm as lymphomas is not known. However, a number of factors have
identified by combined approach of clinical features and been implicated:
morphologic, cytogenetic and molecular characteristics,
rather than location of the neoplasm (whether in blood or in 1. HEREDITY. There is evidence to suggest that there is
tissues) because of the fact that haematopoietic cells are role of family history, occurrence in identical twins and
present in circulation as well as in tissues in general, and predisposition of these malignancies in certain genetic
lymphoreticular tissues in particular. syndromes: