Differential Diagnosis for Right Breast Lump with Skin Redness and Non-Tender

• Single Most Likely Diagnosis
  • Inflammatory breast cancer: This is a highly aggressive form of breast cancer that presents with rapid onset of erythema (redness), edema, and warmth of the breast skin, often without a distinct lump. The non-tender nature and skin redness are key features that point towards this diagnosis.
• Other Likely Diagnoses
  • Breast abscess: Although typically tender, a breast abscess can present with skin redness and a lump. The absence of tenderness does not rule out this diagnosis, especially if the patient is on antibiotics or has a partially treated infection.
  • Mastitis: This is an inflammation of the breast tissue, which can be infectious or non-infectious. It often presents with redness, swelling, and sometimes a lump, but the lack of tenderness might make this less likely.
  • Fat necrosis: This condition can mimic breast cancer and presents as a lump, often with skin retraction or redness. It usually follows trauma to the breast but can occur spontaneously.
• Do Not Miss Diagnoses
  • Necrotizing fasciitis: Although rare, this is a life-threatening infection of the skin and subcutaneous tissue that requires immediate attention. The presence of severe pain (which might not always be present early on), redness, and swelling should prompt consideration of this diagnosis.
  • Advanced breast cancer with skin involvement: Any form of breast cancer that has progressed to involve the skin can present with redness and lumps. Missing this diagnosis could significantly impact treatment and prognosis.
• Rare Diagnoses
  • Granulomatous mastitis: A rare inflammatory condition of the breast that can mimic cancer or infection, presenting with lumps, redness, and sometimes nipple retraction.
  • Sarcoidosis of the breast: Sarcoidosis is a systemic disease that can rarely affect the breast, presenting with lumps or skin changes, including redness.
  • Lymphoma of the breast: Although extremely rare, lymphoma can present in the breast tissue and might cause lumps, redness, or other skin changes.