When diagnostic clues are hidden in small blood vessels of the skin: diagnostic challenge in intravascular large B-cell lymphoma.

Intravascular large B-cell lymphoma (IVLBCL) is a rare extranodal lymphoma characterized by selective growth of neoplastic lymphocytes within small vessels, often lacking lymphadenopathy or circulating malignant cells. Its clinical heterogeneity and nonspecific symptoms frequently cause delayed diagnosis and treatment. We report three older patients presenting with unexplained anaemia, with systemic symptoms in two patients and purpuric skin lesions in one. All were diagnosed via skin biopsy (a purpuric lesion, haemangioma-like lesion and random normal skin, respectively), which revealed intravascular atypical B cells. Two patients developed haemophagocytic syndrome (HPS), aligning with the Asian variant of IVLBCL. One patient had haemangioma-like nodules and lymphadenopathy. These patients highlight the clinical heterogeneity of IVLBCL and emphasize the diagnostic value of skin biopsy in patients with features of HPS (unexplained fever, cytopenia and elevated lactate dehydrogenase or ferritin).