Multimodal assessment of mammogram, ultrasound and clinical palpation in relation to pathological size of breast carcinoma

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Purpose
Breast cancer is the most common cancer in women globally (1) and in Malaysia, being the most commonly diagnosed cancer in the female population and making up 29.9% of all new cancers (2).
Breast cancer screening in Malaysia is opportunistic as there is no comprehensive breast screening programme for the community. Patients may present for screening purposes or with breast symptoms. In the presence of a symptom such as a lump, triple assessment is undertaken, which includes clinical evaluation, mammography, ultrasound and pathological examination (cytology with or without histology). This study aims to evaluate the accuracy of these 3 modalities (clinical palpation, ultrasound and mammogram) in assessing the size of palpable breast cancer lesions compared to pathological measurement, which is an accepted gold standard. Size plays an influential role in breast cancer assessment and management in 3 main aspects, clinical staging, choice of surgical technique, feasibility and planning of non-surgical technique (3). Clinical staging aided by imaging drives the decision for mastectomy or breast conserving surgery, both of which are significant life-changing procedures for the patient. Nonsurgical treatments include neoadjuvant chemotherapy and upcoming technique of ablation of early stage tumours . These methods rely heavily on imaging, especially in ablation in which imaging is the sole guide to planning and execution of treatment (4).

Methods and Materials
A prospective study to compare ultrasound, mammogram and clinical breast tumour size measurements with pathological measurement was carried out from December 2009 until December 2011 in the Department of Biomedical Imaging and Department of Surgery at University Malaya Medical Centre.

Discussion
As stated in the results, ultrasound measurements was the closest representation of pathological size, followed by clinical and mammogram measurements. The results of this study were comparable to other studies by Fornage and Pierie et al in which ultrasound also showed the best correlation with similar r values (5,6). It was also evident that ultrasound and clinical measurements tended to under and overestimate the lesions respectively which was statistically significant. In all the modalities, it can be deduced that as the size of the lesion increases, error in size measurement magnifies. The analysis of clinical T staging versus pathological T staging showed that most modalities predicted the pathological staging correctly.
Multiple factors are responsible for the discrepancies in size between modalities. They include: • Size of the tumour, with lower correlation at extremes of tumours size • Inter-operator variability of ultrasound and clinical measurement (7) • Thickness of skin folds and subcutaneous tissue, particularly in smaller lesions and obese patients during clinical palpation(8) • Mammographic magnification factors (7) • Inaccurate plane of imaging in mammography (7) and dissection in pathology with respect to tumour • Poorly defined tumour margins • Shrinkage of size during formalin fixation and paraffin embedding (9) • Tumour growth during period between imaging and surgery Ultrasound was revealed to be the modality with the closest measurement to pathology size followed by mammogram and clinical palpation. An overall equation to estimate pathological size from ultrasound size was derived from the data which may help in future clinical staging in our centre. These results further establishes the combined role of all three modalities in assessing these tumours.