Possibilities of mammography, ultrasound, and MRI in the differential diagnosis of microcarcinomas of various biological subtypes of invasive breast cancer

Objective: to study the radiological and sonographic features of microcarcinomas of various biological subtypes. Materials and methods. The analysis included 59 patients (median age – 55 years) with invasive breast cancer (BC) pT1a–bN0M0 stages at the N.N. Blokhin Russian Cancer Research Center. The frequency of distribution of luminal A, luminal B HER2 negative, HER2 positive (HER2+) and triple negative subtypes of BC was 39 %, 23.7 %, 23.7 % and 6.8 %, respectively. The analysis of key radiological characteristics and sonographic features of microcarcinomas with different biological structures associated with the diagnosis according to the BI-RADS criteria was carried out. Results. Tumors with luminal A and B subtypes had the most characteristic of malignancy (presence of a node ± microcalcinates), which allowed us to establish the category of BI-RADS 4–5 in mammography (MMG) in 82 % and 88.9 % of patients, respectively. Triple negative cancer is characterized by the presence of a node without microcalcifications; the BI-RADS 4–5 category is exposed in 75 % of cases. Maximum of the difficulties noted in the diagnosis of HER2+ subtype: 4 type density BC (18.2 % of cases), absence of tumor site during surgery in 57.1 % of cases and atypical characteristics of the node (16.7 %) and iso/hypodense structure node (33.4 %) resulted in high frequency of false-negative results in MMG (BI-RADS 0–3 35.7 %), p = 0.049. In addition, HER2+ early BC has proven to be the most difficult subtype for sonographic diagnosis too. The absence of a tumor node in sonography in 14.2 % of cases, as well as its atypical characteristics (iso/hyper echogenicity in 16.7 % of cases and the absence of an acoustic shadow in 18.2 % of patients) led to a high frequency of BI-RADS 0 (21.4 %), which required further examination of these patients. Conclusions. HER2+ early BC was the most difficult biological subtype for MMG and sonographic diagnostics