Differential Diagnosis for the Patient's Rash on the Breast
- Single most likely diagnosis
- Inflammatory breast cancer (IBC): This is the most likely diagnosis due to the patient's presentation of a rapidly spreading, pruritic rash on the breast, associated with erythema and edema, without a palpable mass. The presence of nontender lymph nodes in the axilla also supports this diagnosis.
- Other Likely diagnoses
- Contact dermatitis: Although the patient has not reported any changes in soaps or laundry detergent, contact dermatitis is still a possible diagnosis, especially given the pruritic nature of the rash.
- Eczema (atopic dermatitis): The patient's symptoms of a pruritic rash could be consistent with eczema, particularly if she has a history of atopic diseases.
- Intertrigo: Given the patient's BMI of 37 kg/m2, intertrigo (an inflammatory rash in skin folds) is a possible diagnosis, especially in the inframammary fold.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed)
- Invasive breast cancer with secondary infection or inflammation: Although the mammogram a year ago was normal, it is essential to rule out underlying breast cancer, which could be presenting with secondary inflammation or infection.
- Lymphoma: Although rare, lymphoma can present with skin lesions and lymphadenopathy, making it a crucial diagnosis not to miss.
- Rare diagnoses
- Granulomatous lobular mastitis: A rare inflammatory condition of the breast that can present with a rash, erythema, and swelling.
- Sarcoidosis: A systemic granulomatous disease that can affect the skin and present with a rash, although it is a rare cause of breast symptoms.