Accuracy of preoperative size prediction in infiltrating lobular carcinoma: comparison of mammography, ultrasound and clinical examination

Objective

Accurate preoperative size measurement of infiltrating lobular breast carcinoma (ILC) is of utmost importance in staging and prognosis. ILC is notoriously difficult to measure by conventional techniques, and surgical excision is often repeated for positive margins.

Method

One hundred patients with biopsy-proven ILC underwent mammography, ultrasound (US) and clinical examination prior to surgery between 2000 and 2005. Correlation between histological and estimated size was determined. Insufficient funding prevented inclusion of magnetic resonance imaging (MRI) as a standard modality.

Results

Over 50% had palpable lesions on examination (n = 53). The most frequent mammographic finding was a mass lesion (n = 45) without microcalcification (n = 40). Pearson correlation coefficients for each modality (mammogaphy, clinical, US) were similar (r = 0.77, r = 0.76, r = 0.61; P < 0001). Paired t tests demonstrated mean size differences of +1.31 mm (clinical, n = 53), -3.18 mm (mammography, n = 70) and -4.23 mm (US, n = 89).

Conclusion

Correlations between estimated and actual tumour size for each modality (mammography > clinical > US) were similar. US and mammography underestimate size; clinical examinations overestimate it. Overall, conventional imaging is not an accurate size predictor of ILC. Studies have shown superiority of MRI in size estimation of ILC. We recommend standard inclusion of preoperative MRI for ILC on this basis.