Evaluation of the effect of peritumoral surrounding parenchymal features on radiological size measurement in breast cancer patients: a multicenter retrospective study (TR-BRC 2023-01).

[PURPOSE] To investigate the effects of radiological, clinical and histological features in the radiological assessment of tumor size in breast cancer, with a particular focus on the effect of surrounding parenchymal features (SPFs).

[METHOD] Patients with SPFs reported in the postoperative pathology reports were included in this retrospective multicenter study. Primary lesions were categorized as invasive, in situ (DCIS) or mixed (invasive + DCIS) carcinoma. Pathological tumor size was accepted as the gold standard and compared with tumor sizes measured on mammography (MMG), ultrasonography (US), and magnetic resonance imaging (MRI), according to the presence or absence of SPFs with or without atypia. The effects of other factors such as mammographic breast density, background parenchmal enhancement (BPE), lesion type, lesion size, tumor grade and patient age were also evaluated.

[RESULTS] There were SPFs in 402/473 patients (85%); and 228 of them (56.7%) had high-risk lesions, of which 196 (48.8%) were lesions with atypia. Overall MRI had the best correlation levels in the presence of SPFs. US had agreement levels close to MRI for invasive and mixed tumors, but not for DCIS. Presence of atypical high-risk lesions decreased the correlation levels of MMG (r = 0.193 vs r = 0.485) and MRI (r = 0.220 vs r = 0.679) in DCIS, and of MRI in mixed tumors (r = 0.718 vs r = 0.848). Correlation levels increased with high patient age, low breast density, low BPE, high nuclear grade for DCIS, and increasing tumor size.

[CONCLUSION] This study showed that surrounding parenchymal findings and high-risk lesions adjacent to the tumor are not only a stimulus for malignant development, but also a biological factor that directly affects the accuracy of tumor size measurement in imaging modalities. The fact that MRI preserves the highest level of correlation with pathology, even in the presence of complex parenchymal structures and high-risk lesions, justifies its consideration as the primary modality in surgical planning.