Impalpable breast lesions diagnosed by mammography: incidence of histologically confirmed malignancy

To evaluate the suitability of currently applied mammographic criteria for the early diagnosis of subclinical tumours by comparing radiological findings with the final histological diagnosis.

Open study.

District hospital, Denmark.

151 Women who underwent needle biopsy of 161 occult breast lesions that had been diagnosed by mammography during the period 1986-90.

Definitive operation if frozen section at the time of needle biopsy indicated malignancy. Radiographic examination of the specimen ensured that the abnormal area had been excised.

Correlation of mammographic and histological findings.

Eight foci showed carcinoma in situ and 33 invasive carcinoma; 10 of the 33 had lymph node metastases. Foci with mammographic masses had a significantly higher risk of malignancy than those without (25/70, 37%, compared with 8/91, 17%, p = 0.005). Spiculated foci with clustered calcifications had the highest risk of malignancy (6/11, 54%). 16/87 foci in women less than 50 years old contained malignant disease compared with 25/74 in women aged 50 or more (p = 0.04). A fifth of the frozen sections contributed nothing to the diagnosis. The incidence of malignant disease in impalpable lesions of a quarter is similar to the reported incidence in palpable mammary tumours, but metastases at the time of diagnosis are appreciably less common (30% compared with 50%).

The currently applied mammographic criteria are particularly helpful to patients under the age of 50.