Differential Diagnosis
The patient presents with a 9-month history of a pruritic and burning rash on the right breast, which has not responded to topical corticosteroids. The rash is described as a scaly, erythematous, 4-cm ulceration involving the nipple and areola with two fissures in the periphery. Given the patient's symptoms and physical examination findings, the following differential diagnoses are considered:
- Single most likely diagnosis
- Paget's disease of the breast: This is a rare form of breast cancer that presents with eczematous changes of the nipple and areola, often accompanied by pruritus and burning. The patient's family history of skin cancer and the appearance of the rash make this a strong consideration.
- Other Likely diagnoses
- Eczema (atopic dermatitis or contact dermatitis): The patient's history of seasonal allergies and the appearance of the rash could suggest eczema. However, the lack of response to topical corticosteroids and the specific location of the rash on the nipple and areola make this less likely.
- Psoriasis: The scaly, erythematous nature of the rash could suggest psoriasis, but the location and the patient's lack of other psoriatic lesions make this less likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Inflammatory breast cancer: This is a rare and aggressive form of breast cancer that can present with skin changes, including erythema and edema. The patient's congested tissues at T1-T4 on the right and the appearance of the rash make this a consideration that should not be missed.
- Nipple adenoma or papilloma: These are benign tumors that can cause skin changes and nipple discharge. While less likely, these diagnoses should be considered to rule out other causes of the patient's symptoms.
- Rare diagnoses
- Granulomatous lobular mastitis: This is a rare inflammatory condition of the breast that can cause skin changes and masses. The patient's symptoms and physical examination findings do not strongly suggest this diagnosis, but it should be considered in the differential.
Given the patient's symptoms and physical examination findings, the most appropriate next step in management would be to perform a skin biopsy (E) to rule out Paget's disease of the breast and other malignant causes of the rash.