P53 PROTEIN EXPRESSION IN DUCTAL CARCINOMA IN-SITU (DCIS) OF THE BREAST

Abnormalities in p53 gene expression have been implicated in many inhe rited and sporadic forms of malignancies in humans. Immunohistochemica l staining using monoclonal antibody D0-7 for the p53 protein expressi on was performed in 81 cases of pure DCIS, 14 benign breast lesions an d 2 cases with normal breast tissue. Expression of p53 protein was det ected in 15 (18.5%) cases of pure DCIS. Thirteen (25%) of the 52 comed o type DCIS showed p53 protein expression compared with 2 (6.9%) of th e 29 non-comedo types (P < 0.02). p53 protein expression was also asso ciated with high nuclear grade (P < 0.001) and high mitotic index (P < 0.05). The pattern of p53 protein staining was diffuse in one comedo type DCIS, regional in 6 comedo types, and focal in the remaining 8 ca ses (6 comedo type and 2 micropapillary type DCIS). The patient with c omedo type DCIS showing diffuse staining has a family history of breas t cancer in the first and second degree relatives (sister and maternal aunt). Clinical follow-up data was available in 52 cases. Follow-up p eriod ranged from 9 to 55 months. Three patients, who were primarily t reated by local excision, have had a documented local recurrence in th e form of residual tumor within a short interval of 5 to 11 months. In all these three patients both the original and the recurrent tumors a re negative for p53 protein expression. The difference in the local re currence rate between p53 positive (0/15) and p53 negative (3/37) case d does not reach statistical significance (p > 0.05). We interpret tha t the local tumor recurrence in these three cases within a short perio d after primary excision is due to the presence of residual tumor at t he excision site and is independent of the p53 gene alteration. It is concluded that p53 protein expression in DCIS is associated with comed o subtype, high nuclear grade, and high mitotic index, and is a promis ing new parameter to evaluate the cellular biology and prognosis of DC IS.