MRI and the pathology of breast invasive micropapillary carcinoma

Diagnosis of breast invasive micropapillary carcinoma (IMPC) before surgery is of great value for determining the optimal treatment strategy. The aim of the present study was to investigate the magnetic resonance imaging (MRI) and pathological features of IMPC. MRI features of IMPC were characterized in relation to the patients' clinicopathological features. Clinical manifestations, mammography results and/or MRI findings of patients with IMPC were retrospectively analyzed. Parameters included morphology, plain T2-weighted imaging (T2WI) signal intensity, the apparent diffusion coefficient (ADC), the internal enhancement mode, early enhancement rates and time-intensity curve (TIC) types during dynamic enhanced scanning. A total of 10 lesions were detected by MRI in eight patients, with one case having three lesions with the mean diameter of 34.44 mm. In plain T2WI scanning, the lesions appeared inhomogeneous with a moderate or high signal intensity. When the b value was 800 sec/mm², the average ADC value was 0.823±0.12×10^-3 mm²/sec. A total of four cases exhibited mass-like enhancement, including an oval rim in one case (three lesions), irregular inhomogeneous enhancement in two cases and irregular uniform enhancement in one case. The margins were clear in one case (three lesions), irregular in two cases and spiculate in one case. Among the four cases with non-mass enhancement, the distribution was focal in two cases, linear in one case and regional in one case, and the internal enhancement mode was cluster-like in one case, heterogeneous in one case and uniform in two cases. The average early enhancement rate was 116.96±45.26%. TICs of type III were observed in all cases. In conclusion, MRI of IMPC demonstrated typical features of malignant tumors and lymphatic vessel infiltration, suggesting that MRI may exhibit guiding significance for the diagnosis and treatment planning of IMPC.