Immunohistochemistry has become a very important, and in some cases indispensable, tool in diagnostic pathology, enabling the precise identification of tumours, the detection of micrometastases in a given sample, and the evaluation of various prognosis factors. However, in some cases, the use of multiple but distinct immunostains can lead to some unforeseen results—for example, the expression of an apparently aberrant marker by a neoplasm can sometimes be seen. In this context, we report our experience with a case of refractory anaemia with excess of blasts in transformation (RAEB-t) in which the blasts were unexpectedly found to express cytokeratin (CK).

An 86 year old woman with a past medical history of breast carcinoma treated by mastectomy and adjuvant radiotherapy was admitted to our institution because of worsening anaemia. The following haematological indices were noticed: haemoglobin, 8.6 g/litre; erythrocytes, 2.5 × 10¹²/litre; white blood cells, 3 × 10 …