The diagnosis of breast cancer in women younger than 40.

This study examined how the diagnosis of breast cancer is different in young women. Records were retrieved for 239 women diagnosed with breast cancer before age 40 and compared with 2101 women aged 40 and over with breast cancer. On mammography, lesions in the younger women were more likely to be undetected or interpreted as benign, especially in women with dense breasts. However, there were 10 young women where impalpable cancers with microcalcification under 10 mm would not have been diagnosed without mammography. An abnormality was detected on ultrasound in 92.2% of cancers in young women, but was more likely to be considered benign than in older women. If ultrasound alone had been used in the young women, at least 18 cancers would have been missed. Ultrasound was useful for predicting the ultimate tumour size at pathology, and for detecting multifocality. There were 14 cases where the ultrasound appearance was indistinguishable from fibroadenoma. The importance of fine needle aspiration cytology in the diagnosis of focal lesions in young women (over 20 years) was confirmed. For symptomatic women, the proportion of breast malignancies under 10 mm was similar in the two groups. However, the younger group had significantly more poorly differentiated tumours.