A 46-year-old woman comes to the office for evaluation of a rash on her breast. For the past 2 months, the patient has had a pruritic rash on her left breast that has slowly spread. She has had no fever, nipple discharge, or recent changes in soaps or laundry detergent. The patient has used a topical antibiotic ointment and a drying powder over the rash but has had no improvement. She has well-controlled type 2 diabetes mellitus and hypertension. BMI is 37 kg/m². The left breast is diffusely enlarged with an area of erythema below the areola that extends to the inframammary fold. There are no palpable breast masses. Two nontender lymph nodes are palpated in the left axilla. The remainder of the physical examination is unremarkable. Mammogram a year ago was normal. Which of the following is the best next step in management of this patient?

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11ec25c8_d892_5bd8_bc81_efb84fe7d2f2_MD0003_00 This patient has a unilateral, pruritic breast rash with breast erythema and edema. Skin changes of the breast can occur due to various etiologies, including infection (eg, mastitis, cellulitis), trauma (eg, breastfeeding), or malignancy. In this perimenopausal patient with axillary lymphadenopathy, the most concerning etiology is malignancy, particularly inflammatory breast carcinoma (IBC), due to the rapid onset of symptoms. IBC is an aggressive breast cancer characterized by invasion of dermal lymphovascular spaces, which causes lymphatic obstruction (eg, axillary lymphadenopathy) and a diffusely enlarged breast with skin edema and fine dimpling (classic peau d'orange appearance). Due to early lymphatic involvement in IBC, there is typically rapid tumor growth and metastasis (ie, within months), with the potential for interval development of IBC between routine mammography screenings (as in this patient). Patients commonly have metastatic disease at initial presentation. Patients with suspected IBC require breast biopsy (eg, core needle biopsy) and full-thickness skin punch biopsy (evaluating for the classic finding of dermal lymphatic invasion) for diagnosis. Due to high rates of metastasis, treatment for IBC is typically aggressive (eg, chemotherapy, mastectomy, radiation). (Choice B) Patients with type 2 diabetes mellitus and obesity are at risk for candidal mastitis or intertrigo, which can be diagnosed with KOH skin scraping. Candidal mastitis classically causes a shiny, flaky areolar rash and shooting breast pain. Intertrigo causes macerated plaques between the inframammary folds with associated satellite lesions. (Choice C) Mammography and ultrasound of the affected breast and axillary lymph nodes are indicated for suspected IBC. However, MRI of the breast is not performed due to low specificity for cancer (ie, both benign and malignant masses appear enhanced). (Choice D) Antibiotics can treat mastitis, which also causes unilateral breast erythema and edema. However, patients also typically have breast pain, fever, and malaise. In addition, axillary lymphadenopathy is uncommon (except in severe cases) and is usually painful (unlike in this patient). (Choice E) Topical steroids can be used to treat contact dermatitis, which is unlikely in this patient with no recent environmental changes. Dermatitis does not cause diffuse breast enlargement or axillary lymphadenopathy. Educational objective: Inflammatory breast carcinoma (IBC) is an aggressive breast cancer that can present with unilateral breast rash, erythema, and edema. Metastatic disease (eg, axillary lymphadenopathy) is common on initial presentation. Patients require core needle breast biopsy and full-thickness skin punch biopsy for diagnosis. References: Dermoscopy of inflammatory breast cancer. (http://www.ncbi.nlm.nih.gov/pubmed/29723370) Inflammatory breast cancer: a literature review. (http://www.ncbi.nlm.nih.gov/pubmed/30524636) Inflammatory breast cancer: new factors contribute to disease etiology: a review. (http://www.ncbi.nlm.nih.gov/pubmed/25685520)

A 46-Year-Old Woman Comes to the Office for Evaluation of a Rash