Artificial intelligence-assisted three-dimensional imaging of breast microinvasive carcinoma reveals larger invasive focus size in a substantial proportion of cases.

Microinvasive carcinoma of breast is a unique type of malignancy characterized by the presence of small invasive foci (less than 1 mm in diameter) in a background of carcinoma in situ. The disease is the earliest stage of breast invasive carcinoma development, and patients diagnosed with this disease are often treated conservatively. However, diagnosing microinvasive carcinoma based on a single tissue section may underestimate the invasive focus size. We developed a three-dimensional (3D) imaging method to re-evaluate the invasive focus size in microinvasive carcinoma cases in which the original reported focus size was close to 1 mm. The 3D images were annotated and used to developed an artificial intelligence (AI) program based on the HRNetV2 architecture to assist in the annotation of future cases. We found that in 8 of 11 cases (72.7 %), the foci sizes are greater than 1 mm when the specimens are analyzed in 3D space, resulting in re-classification of the cases as T1a invasive carcinoma. Notably, in one of the reclassified cases, isolated tumor cells were identified in the sentinel lymph node biopsy. Our findings challenge the robustness of the microinvasion concept and indicate that AI-assisted 3D imaging is a valuable tool in precision diagnosis of microinvasive carcinoma.