Cutaneous Blastomycosis Mimicking Breast Malignancy

Blastomycosis is a fungal infection caused by Blastomyces dermatitidis. While blastomycosis can cause systemic infection affecting multiple organs, localized blastomycosis of the breast is uncommon. Here, we report the case of a 50-year-old female with a localized left breast growth which started as a nodule and later ulcerated extensively. Although her clinical picture raised concerns for breast malignancy, workup revealed cutaneous blastomycosis with superimposed methicillin-susceptible Staphylococcus aureus and Klebsiella oxytoca infection. Interestingly, there was no evidence of pulmonary disease on CT chest imaging. She was treated with Amphotericin B for seven days and discharged on oral Itraconazole for nine months. Additionally, she received amoxicillin-clavulanate for her bacterial superinfection. On the six-month follow-up, the patient showed significant improvement. Blastomycosis can mimic several diseases including malignancy, pyoderma gangrenosum, and mycobacterial and bacterial infections leading to delayed diagnosis and treatment.