PA40 B-cell lymphoblastic lymphoma in a paediatric patient

Abstract A 5-month-old girl presented with two progressively enlarging scalp lumps over 2 months. Initially treated for a scaly patch with topical antifungals, she was later referred to dermatology, where a firm 2 × 2-cm subcutaneous nodule was noted. Ultrasound revealed fluid accumulation beneath the skin, and a biopsy taken during the visit revealed soft, rubbery material. Histology confirmed B-cell lymphoblastic lymphoma (B-LL), with blasts showing immunohistochemical positivity for CD79a, PAX5 and CD19. Bone marrow biopsy showed minimal infiltration (0.04%), and cerebrospinal fluid was negative for lymphoma cells. She was transferred to a specialist paediatric haemato-oncology centre and started on the UKALL protocol with an initial positive response to chemotherapy. B-LL is a rare disorder affecting young children, usually aged < 6 years, with a slight male predominance. It is characterized by lymphoblast infiltration, primarily in lymph nodes, and less commonly the bone marrow, unlike acute lymphoblastic leukaemia (ALL). The exact cause is unclear, although associations with genetic mutations (GATA3, CEBPE, ARID5B, IKZF1, CDKN2A) and environmental factors, such as ionizing radiation, are reported, especially in children with Down syndrome. B-LL often presents without symptoms and can manifest in the skin, soft tissue or lymph nodes. Early diagnosis of B-LL can be difficult due to its asymptomatic nature, often leading to delays in treatment. Prognosis is influenced by age, clinical presentation and genetic abnormalities, with infants carrying KMT2A translocations facing a poorer outlook. Prompt recognition and initiation of appropriate treatment, such as the UKALL protocol, are crucial in improving outcomes for paediatric patients.