Paget's disease of the breast masquerading as squamous cell carcinoma on cytology: a case report

Paget's disease is an uncommon manifestation of breast carcinoma occurring in 1-2% of female patients with breast cancer. Here, we present a case of Paget's disease of the breast, which was initially interpreted as squamous cell carcinoma on cytology. This case report raises two issues. First, histological and cytological specimens of Paget's disease show a mixed population of epithelial cells including squamous cells with reactive changes and malignant glandular cells. In the current case, a mixed population of atypical keratinizing and nonkeratinizing epithelial cells was initially interpreted as squamous cell carcinoma of cutaneous origin. The marked reactive changes in the squamous epithelium involved by Paget's disease should be recognized. Second, this case is an unusual clinical presentation for Paget's disease of the breast as the nipple-areolar complex and underlying breast tissue were surgically absent at the time of diagnosis. Clinical suspicion, along with an awareness of the cytologic features and clinical presentation of Paget's disease, can help in reaching the correct diagnosis in a timely fashion.