P26 Leukaemia cutis as the first manifestation of acute myeloid leukaemia

Abstract

Abstract Leukaemia is the most frequent malignancy of childhood, accounting for approximately 30% of all malignancies. Acute leukaemia may present in a variety of extramedullary manifestations, the commonest being leukaemia cutis (LC). LC is the infiltration of the epidermis, dermis or subcutis by neoplastic leukocytes with skin lesions preceding the development of leukaemia in the peripheral blood or bone marrow in just 2–3% of cases. A 6-month-old baby girl was reviewed due to multiple skin lesions which appeared on her left forearm 2 months previously, and spread widely, showing over 50 in the following weeks. They were well-circumscribed, nontender, violaceous nodules. She was clinically well and thriving with no lymphadenopathy or organomegaly. Blood tests and abdominal ultrasound were normal. A skin biopsy of a nodule demonstrated an infiltrate of medium-sized atypical cells involving the dermis and subcutis. Immunostaining showed CD45 expression and the Ki67 proliferation index was high, in keeping with a leukaemic infiltration. Cytogenetics performed on the skin biopsy showed KMT2A rearrangement by FISH. Bone marrow aspirate confirmed the diagnosis of acute myeloid leukaemia with monoblastic morphology, and cytogenetics confirmed the rearrangement as a KMT2A–MLLT10 fusion, which is classified as poor cytogenetic risk. Cerebrospinal fluid analysis was negative. It is vital to get a histological diagnosis (with cytogenetics) in a child presenting with violaceus nodular lesions even if the child is well. Importantly, LC can present with a normal full blood count. A bone marrow aspiration is paramount to confirm the diagnosis. Once leukaemia is diagnosed, cytogenetics plays a key role in stratifying treatment intensity.