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Classification of haematological malignancies

Haematological malignancies (blood cancers) are the fifth most common cancer group in economically developed regions of the world. They are traditionally categorised by site according to whether cancer is first detected in the blood (leukaemias), lymph nodes (lymphomas - Hodgkin and non-Hodgkin) or bone (myelomas). This topographical, or site-based, subdivision (currently ICD-10) is commonly used by cancer registries to describe the burden of disease in the population as a whole. Data from England, Wales and Scotland are shown in the pie chart below. Click the button to see the data for males and females separately.

In 2001, WHO produced a new paradigm-changing consensus classification (Classification of Tumours of Haematopoietic and Lymphoid Tissues) that defined haematological malignancies according to their presumed cell of origin, genetic abnormalities, and clinical features. This classification defines over 100 clinically-meaningful subtypes and forms the basis for the morphology-based haematological malignancy codes in the 3rd Edition of the International Classification of Oncology (ICD-O-3). The ICD-O-3 classification is used for all diagnoses within HMRN and a table of ICD-O-3 codes, together with more information about them, is included in our Resources section.

The pie chart below shows the relative frequencies of the main ICD-O-3 haematological malignancy subtypes in HMRN. Click the 'ICD-10 groups' button to see how these relate to the traditionally used groups.

As shown in the pie charts, the traditional ICD-10 groupings contain a mix of ICD-O-3 subtypes. Most notably, the ICD-10 leukaemia group (red) incorporates myeloid and lymphoid subtypes; which differ markedly from each other. For example, acute promyelocytic leukaemia, a myeloid neoplasm, has a median diagnostic age of 50 years, occurs with equal frequency in men and women, and is curable but rapidly fatal if not treated immediately. However, chronic lymphocytic leukaemia, a more common mature B-cell neoplasm, has a median diagnostic age of 72 years, is twice as likely to occur in men than women, and is currently incurable but often managed by active monitoring alone.

In addition to including fundamental changes to previously defined categories, ICD-O-3 also recognises several new entities, some of which are coded as “neoplasms of unknown or uncertain behaviour” in ICD-10 (dark grey in the ICD-10 pie chart). Furthermore, ICD-O-3 also recognises the premalignant disorders (light grey) monoclonal B-cell lymphocytosis and monoclonal gammopathy of undetermined significance, which HMRN also collects data on.