• Immunohistochemistry
• leukaemia

Fetal haemoglobin (HbF) is an established tumour marker of erythroid lineage in various malignancies, including leukaemia.1 γ-Globin gene reactivation has been found to occur during the differentiation of various leukaemia cell lines,2–4 suggesting that leukaemia blasts, unlike their normal analogous cells, have the potential to differentiate into HbF cells. To assess this hypothesis, as well as to observe the distribution of HbF cells in malignant conditions, we performed the present immunohistochemical study in the bone marrow and spleen of leukaemia patients.

The programme of research, including studies on archival and stored materials, was approved by the Research Ethics Committee of the East London and City Health Authority. Histopathological specimens included bone marrow trephine biopsies and surgical specimens of spleen tissues from patients with leukaemia or lymphoma. By reviewing the records of chemotherapy administration, care was taken for all histological specimens examined to exclude patients treated with any chemotherapy in the previous 6 months. For immunohistochemical detection of HbF, we used the peroxidase-labelled avidin-biotin method, as previously described,5 changing only the source of affinity purified, polyclonal, sheep antihuman HbF primary antibody (Abcam, Cambridge, UK). As usual, the immunostaining specificity was confirmed by controls of omitting the primary antibody. Bone marrow biopsies from 72 patients with myeloid leukaemia (40 acute myeloid leukaemia (AML) and 32 chronic myeloid leukaemia (CML)) and 43 patients with lymphoid leukaemia (21 acute lymphoid leukaemia (ALL) and 22 …