The hidden breast lesions: A case report of bilateral breast cancer

Abstract Bilateral breast cancer (BBC) is rare and is associated with an unfavorable prognosis. Consequently it is crucial to improve diagnostic performance of breast cancer in the clinical setting. We report a case of BBC in a 66‐year‐old woman and describe the imaging findings, including mammography, hand‐held ultrasound, automated breast ultrasound, anatomical intelligence for breast ultrasound (AI‐breast), and magnetic resonance imaging. Only AI‐breast ultrasound successfully located the two tumors, while other imaging examinations failed to detect the tumor in the right breast.


| INTRODUCTION
The occurrence of bilateral breast cancer (BBC) is increasing nowadays with a reported incidence ranging between 1.4% and 12%. 1,2 However, in recent literature, patients with BBC showed a significantly worse distant relapse-free survival (RFS) as compared to those with unilateral breast cancer (UBC), as distant metastases were frequently reported in patients with BBC. 2,3 Early detection and treatment of BBC is important to improve the overall prognosis of patients with breast cancer. US-guided biopsy was performed on the two lesions, and histological examination results revealed both were invasive breast carcinoma (non-special type, NST). The patient underwent double mastectomy, and intraoperative sentinel node biopsy was negative.

| CASE REPORT
Surgical specimens of the lesions were stained for pathological confirmation. The lesion in the left breast was invasive breast carcinoma (NST) measuring 14 mm (stage III, Figure 6) and the lesion in the right breast was also revealed to be invasive breast carcinoma (NST) measuring 6 mm (stage II, Figure 7). The bilateral breast lesions were missed by HHUS screening at another hospital. The accuracy of breast screening is related to the radiologist's experience. In this case, the most important reason for missed diagnosis of the left breast lesion was the lack of understanding of a non-mass lesion, which is defined as a discrete and identifiable area which shows altered echotexture compared with that of the surrounding breast tissue and does not conform to a mass shape. The failure to detect the tumor in the right breast by HHUS screening might be caused by atrophy of the patient's breast glands and the particular position of the tumor. The tumor was located in the marginal area of the breast and no obvious glandular tissue was observed surrounding it. In breast US scanning, the general radiologist usually takes the margins of glandular tissue as reference to identify the margins, leading to insufficient coverage. Another reason for the mis-detection might be that the sonographers were more focused on evaluation of the palpable tumor in the left breast due to the relative low incidence of BBC and evaluation of the right breast was therefore lax. Standardized scanning reducing human errors or biases are important in breast US scanning. [10][11][12] AI-breast US 13  Thirdly, all of the breast US scanning data can be recorded in AIbreast, including auto-annotation of the lesion information, bookmarks of key frames within the loop, and quick access to the orthogonal plan from a reference point, which makes the longitudinal followup of patients with breast lesions more convenient.
Cases of BBC are rare, and early diagnosis, which can significantly improve disease-specific survival, depends on breast imaging. The most common method of screening for breast cancer in Asian women is US, but the performance of ultrasonologists varies to a large extent.
Unlike HHUS, AI-breast US uses a reproducible and less operatordependent process for image acquisition. In this case, AI-breast US demonstrated its value in the detection of BBC, indicating its advantages in the diagnosis and follow-up of patients with bilateral breast lesions. Meanwhile, with the trial to separate the screening procedure and detection or diagnosis procedure in this study, AI-breast may initiate new workflows for breast US examination to improve coverage.
Misdiagnosis and missed diagnosis are common in cases of BBC because of lack of attention to the contralateral breast after observation of a suspect lesion. Sonographers must not be satisfied with finding just one lesion, but must search carefully for others, whether ipsilateral or contralateral.

DATA AVAILABILITY STATEMENT
All data and images generated or used during the study appear in the submitted article.