Of 116 recurrences examined, 61 (53%) were DCIS and 55 (47%) were invasive. Of these 116, 103 (89%) occurred near the site of the original resection. Comparing the primary DCIS and the recurrence, concordant histology was found in 62%. Although 11% of the recurrences developed at a distance from the primary DCIS, nearly all these showed the same histological and immunohistochemical profile. Well differentiated DCIS progressed towards poorly differentiated DCIS or grade III invasive carcinoma in 4 cases, whilst in 5 cases poorly differentiated DCIS or grade I invasive carcinoma. Identical marker expression (oestrogen receptor and progesterone receptor status and HER2/neu and p53 overexpression) was found in 45 out of 71 (63%) cases assessed. As, in most cases, primary DCIS and local recurrence were closely related, either histologically or by marker expression, the authors concluded that local recurrence probably reflects outgrowth of residual DCIS.