Consideration of the process of lymph node metastasis in invasive breast cancer with squamous cell differentiation

Background Breast cancer with squamous differentiation is a relatively rare condition. Clinically, lymph node metastasis is uncommon in metaplastic carcinoma We treated a patient with lymph node metastasis of the ductal carcinoma component of invasive ductal carcinoma with squamous cell differentiation. Case Report An 84-year-old postmenopausal Japanese woman had a left-breast mass with an enlarged lymph node in the left axilla. A biopsy revealed an invasive ductal carcinoma with squamous cell differentiation. A left mastectomy with axillary lymph node dissection was performed. The histologic evaluation revealed invasive ductal carcinoma with squamous cell differentiation. One lymph node was positive for metastasis consisting of ductal carcinoma without squamous cell differentiation. Conclusion This case suggests that lymph node metastasis in ductal carcinoma with squamous differentiation may first involve the ductal carcinoma component, and then differentiation may occur in the involved lymph nodes. This is an interesting case highlighting the process of the progression of lymph node metastasis in cases with breast cancer with squamous cell differentiation.