The Get Data Out programme routinely publishes cancer statistics produced by NHS E (previously PHE and NHS D) in a consistent table, called the Get Data Out (GDO) table. This table collects patients into groups with common characteristics, and then publishes information such as incidence, treatment rates, survival and Routes to Diagnosis for these groups.

This document sets out the definitions of the cohort and groups for the Get Data Out tables for the 2023 release of data on haematological malignancy (HM) transformations between 2013 and 2020.

Haematological malignancy transformations cohort

The cohort of haematological malignancy transformations used for Get Data Out is all haematological malignancy tumours identified as having undergone a transformation event between 2013 and 2020 from a different type of haematological malignancy (as defined in the Haematological malignancy Get Data Out group) diagnosed between 1995 and 2020. For methodology on how to count haematological malignancies see the “Counting Haematological Cases SOP 2.0.pdf” document which can be found in the data releases table on the main technical page.

Historically, it has been challenging for cancer registries to systematically capture the registration of multiple tumours, which is particularly true for haematological malignancies (HM) where patients may have relapsed disease, developed a secondary neoplasm or their disease has undergone progression or transformation.

To date there is no uniform definition of the transformation of haematological malignancies1. However, the basic principle of a transformation is that a tumour cell, subject to a complex combination of genetic mutations, can undergo a process of clonal evolution that profoundly changes the architecture of the cell and results in a transformation to a different tumour type2. Transformations are generally thought of as any slow-growing (low-grade) disease that changes into a faster-growing (high-grade) disease.

In the past, NDRS have captured transformation events as a separate primary disease registration when a new diagnostic group has emerged. However, following consultation with Laboratory Information Management System Suppliers and the Chair of the Royal College of Pathologists (Working Group on Cancer Services), alterations were made to the structure and contents of the Cancer Outcomes and Services Dataset (COSD) dataset. Such changes included the recording of transformation events, to conform to the recommendations provided by the European Network of Cancer Registration, published in February 20143. These changes were reflected in COSD v9.0, released in April 2020; where the option was created to record a transformation event, affecting cancer registry data from 2018. This change in rules meant that a transformation is to be recorded if the first haematological malignancy transformed into a new morphological entity after a three-month window of the first registration. As such, only the first tumour’s morphology and date of diagnosis are to be considered as incident for analysis and reporting.

To allow for greater consistency of reporting, the NDRS decided to create a lookup table of HM capable of transforming using guidelines developed by Gavin et al which offer additional coding parameters to the rules defined in the Haemacare manual4. Here, transformations events were defined using the International Classification of Disease Oncology (ICD-O) 3rd edition, first revision5 and mapped back to ICD-O-2 descriptions of disease for patients diagnosed between 1995 and 2012, so that lower-grade / indolent diseases (slow growing) where the time to transformation can be measured in decades can included in our analysis.

To account for variation in the recording of diagnosis dates, which can be the date the diagnosis was confirm at multi-disciplinary team meetings or signed off by the senior pathologist, a transformation event can be recorded up to 31 days before the precursor condition, or any time afterwards.

In order to provide a reliable haematolgoical time series, cases pre-2018 that would now be registered as transformation events were identified and removed from the primary haematological malignancy time series.

Transformations are identified in one of two ways:

  1. Imputed from a pair of primary tumours (for diagnoses pre-2018)
  2. Extracted from the ENCORE Transformations table (for diagnoses post-2018)

Pairs of primary tumours that suggest a transformation event were identified by following the transformation rules specified in the National Cancer Registration and Analysis Service (NCRAS) Haematology guidance. These rules come from Gavin et al., (2015) and are available in the table in the Appendix. If a single patient has a pair of tumours defined as a transformation by Gavin et al., (2015) the first one is assumed to be the primary tumour and the second is included as a transformation. The two most common types of transformation are those to acute myeloid leukaemia and diffuse large B-cell lymphoma.

For more information on the different transformation events, see the “Haematological Malignancy Descriptions.pdf” document which can be found in the data releases table on the main technical page. The groupings for the haematological malignancy transformations cohort are summarised below.


The cohort is first split by the year of diagnosis of the transformation tumour.

Tumour Type 1

Haematological malignancy transformations were then partitioned by the resulting tumour type, post transformation. This was based on morphology and behaviour as coded in ICD-O-3 and split into:

Tumour Type 2

These transformation subgroups were then split into the types of tumour that they originated from.

Acute myeloid leukaemia (AML) is partitioned into:

Diffuse large B-cell lymphoma (DLBCL), Hodgkin, and other high grade is partitioned into:

These classifications are made on ICD-O-3 morphology and behaviour following the Get Data Out haematological malignancy Tumour Types (as defined in the Haematological malignancies grouping document).

The ‘Other transformations’ Tumour Type 1 group was not partitioned further due to small numbers.


Transformation events based on Gavin et al., 2015. ICD-O-2 and ICD-O-3 morphology and behaviour codes for precursor and transformation tumours