On the occurrence of focal, occult in situ and invasive carcinoma in 250 mastectomy specimens.

In 1982, a total of 250 breasts were removed for cancer in the surgical departments of the Oslo City Health Department, comprising 81% of all new breast cancers reported in Oslo in 1982. Invasive ductal carcinoma (68%) and invasive lobular carcinoma (12.4%) were the predominant types. Special attention was given to the presence of occult in situ or invasive carcinomas more than 1 cm from the periphery of the main carcinoma. In 24.8% of the specimens, carcinoma in situ was found in such locations, and an additional 6.9% showed a second, occult invasive carcinoma. Carcinoma in situ was equally common in invasive ductal and invasive lobular carcinoma. Occult invasive carcinoma was predominantly found in specimens with invasive lobular carcinoma. There was a significantly increased number of lymph node metastases in patients with carcinoma in situ or second, occult primary carcinoma more than 1 cm from the periphery of the main carcinoma.