The value of MRI compared to mammography in the assessment of tumour extent in invasive lobular carcinoma of the breast.

Abstract

AIMS: Invasive lobular carcinoma of the breast (ILC) is known to be substantially underestimated by mammography, which makes correct planning of treatment difficult. MRI has been proposed as a valuable adjunct to mammography. The purpose of the current study is to evaluate its value, compare it to mammography and assess the possible causes of over- and underestimation of lesion size on MRI. METHOD: The mammograms and MRI scans of 67 consecutive patients with ILC were retrieved and re-evaluated. Size measurements were correlated to the sizes extracted from the pathology report. RESULTS: MRI measurements correlated better to pathologic size (r=0.85) than mammographic measurements (r=0.27). Underestimation of tumour size was more common on mammography (p<0.001); overestimation occurred with equal frequency (p=0.69). Overestimation on MRI, caused by non-malignant findings, was attributed to enhancing lobular carcinoma in situ. CONCLUSION: MRI is a more accurate modality for determining tumour size in patients with ILC than mammography. The typical underestimation of lesion size by mammography can be prevented with the aid of MRI, without increasing the risk of lesion overestimation.