Breast malignancy masquerading under the cloak of acute urticaria.

Urticaria is a common disorder characterised by well-demarcated and intensely pruritic erythematous skin swellings. Common triggers include infection, allergic reactions or medications. While often idiopathic, the presence of urticaria can be associated with underlying systemic disease. We report a case of a patient who presented with diffuse and refractory urticaria. A thorough workup was conducted to determine the aetiology including routine age-appropriate cancer screening. Mammography revealed four lesions in the patient's left breast with biopsy consistent with invasive ductal carcinoma. Disappearance of the urticarial lesions with mastectomy suggests an association between breast malignancy and urticaria. Thus, refractory urticaria with unknown cause should prompt a thorough history, physical examination and review of age-appropriate cancer screening.