Carcinoma Erysipeloides: An Underdiagnosed Phenomenon of Cutaneous Metastases of Breast Cancer.

BACKGROUND Cutaneous metastatic breast cancer is a rare manifestation. Causes include vascular or lymphatic spread or iatrogenic mechanisms following surgery. A sub-type of this disease process, "Carcinoma Erysipeloides," represents subcutaneous and dermal tissue layer invasion via lymphatic spread. Diagnosis can be challenging, and therefore, obtaining a thorough history and physical, with careful inspection of prior surgical scars is essential for an accurate diagnosis. Lesions present in variable ways, including papules, plaques, ulcerations, nodules, crusting, or fungating masses, with common locations in the chest, scalp, abdomen, and less commonly the arms. When carcinoma erysipeloides is identified, it is imperative to evaluate for distant metastases. Recent literature has identified benefits with trastuzumab deruxtecan therapy instead of trastuzumab emtansine, with decreased progression rates and decreased mortality rates. Metastasis to the skin can indicate advanced disease; however, this metastatic site may be preferable to visceral organs or bones in terms of prognosis. CASE REPORT We present a rare manifestation of metastatic breast cancer in 45-year-old Hispanic woman, status post neoadjuvant chemotherapy and radical cystectomy on maintenance trastuzumab and pertuzumab. We discuss the clinical presentation variability, keys to diagnosis, treatment considerations, and outcomes for this unique patient population. CONCLUSIONS Carcinoma erysipeloides varies in clinical presentation, especially when patients develop exclusive skin lesions. We identify common etiologies for this progression of disease and discuss combination therapy which has demonstrated a reduction in mortality in this patient population.