Incidental Carcinomas and Lesions with Uncertain Malignant Potential (B3) Discovered During Symmetrization Mammoplasty in Breast Cancer Patients—Retrospective Single-Center Experience

Although occult breast carcinomas and lesions with uncertain malignant potential are rare, their incidental discovery during symmetrizing mammoplasty can significantly alter the treatment approaches and cancer staging. In the context of oncoplastic surgery, the systematic evaluation of the contralateral breast is a clinical priority that has been underexplored in Eastern Europe. Background/Objectives: This study aimed to assess the incidence and histological characteristics of incidental carcinomas and B 3 lesions detected during contralateral symmetry mammoplasty in patients with breast cancer. Methods: This retrospective study was conducted at the Plastic and Reconstructive Surgery Clinic of the “Pius Brînzeu” County Emergency Clinical Hospital in Timisoara, Romania, over six years (2018–2024), and included 180 of 256 patients who underwent contralateral breast symmetrization. Results: Among the 180 patients, 21 (11.66%) had incidental findings: eight (4.44%) had contralateral carcinomas, and 13 (7.22%) had B3 lesions. The histopathological types identified were invasive ductal carcinoma NST (one case), ductal carcinoma in situ (one case), invasive lobular carcinoma (five cases), and mucinous/papillary carcinoma (one case). Compared to the reported international range of 2–10%, our observed incidence of 11.66% reflects the unique aspects of our patient cohort and the thoroughness of our histological analyses. Conclusions: Detection of contralateral carcinomas and B3 lesions during symmetry mammoplasties underscores the importance of a multidisciplinary approach, comprehensive bilateral screening, and detailed histopathological examination of specimens.