In the past, the diagnosis of ductal carcinoma in situ (DCIS) was rare, but today the incidence of DCIS has become much more frequent, particularly in patients who underwent mammographic screening. The management of patients with DCIS has become a major clinical dilemma. It has become increasingly difficult to justify the routine use of mastectomy for patients with DCIS, because its natural history is uncertain and breast-conserving therapy (BCT) is currently used for the treatment of many patients with invasive breast cancer.

To investigate the incidence, clinicopathologic features and the outcome of treatment of DCIS and microinvasive carcinoma (MIC), the medical records and pathology slides of 91 patients with DCIS and MlC who had been treated at KCCH between 1983 and 1996 were reviewed retrospectively. Median follow-up period was 69.4 (4-158) months.

The results were as follows; 1) The incidence was 2.72% (91/3.343) and had been increasing (2.1% in 1980s and 3.3% in 1990s). 2) The mean age was 44.2 years and peak age group was fifth decade. 3) The most common clinical features was a palpable mass (69%), followed by nipple discharge, MMG abnormality and Paget's disease in decreasing order of frequency. 4) According to the pathologic classification of Schwartz, comedo type was the most common (32%), followed by cribriform (23%), papillary (20%), mixed (11 %), solid (9%) and micropapillary type (5%), 5) There were 58 cases (69%) of pure DCIS and 16 cases (17.5%) of MIC. In 17 cases (18.5%) the presence of microinvasion was equivocal or could not be assessed. 6) There were no significant differences between DCIS and MIC in terms of mean age (44.5 years vs 43.8 years), mean tumor size (2.15 cm vs 2.25 cm), the frequency of comedo type (29% vs 36%), lymph node metastasis (0% vs 6%) and multicentricity (3.3% vs 3.0%). However, the palpable mass was more common in MIC than DCIS (82% vs 62%, p<0.05). 7) 75 patients (82%) were treated with mastectomy and 16 patients were treated with breast conserving surgery. 8) Bedsides 2 cases of systemic recurrence among MIC, there was no case of recurrence or disease-associated death during the period of follow-up.

The incidence of DCIS and MIC showed increasing tendency primarily due to the increasing use of screening mammography. Even though the rates of BCT has been increasing, MRM was still the most common procedure for the treatment of DClS and MIC. The outcome of treatment, in terms of recurrence or survival, was very excellent and almost the same for both groups of pure DCIS and MIC. More long-leno follow-up and multicenter study seems to be neccessary to identify the differences in clinical features and outcome between pure DCIS and MIC in Korea.