A 77-year-old woman presented with a 10-month history of nontender, nonprogressive erythema and induration of the left breast that she had first noticed 4 months after she had completed a course of radiotherapy following a lumpectomy and chemotherapy for a 3-cm, poorly differentiated, infiltrating ductal carcinoma of the left breast. The tumor was found to be stage IIB, with 2 axillary sentinel nodes that were positive for metastases, which had been identified only on immunohistochemical analysis. There was no evidence of systemic metastases.