Discussion

This case highlights two important clinical issues. First, in cases in which US does not show any mass after breast augmentation with silicone injection, CD should be used to detect hypervascularised areas. Second, to prevent false-negative biopsy results, it is important to perform CD to identify hypervascularisation that suggests cancer at suspected sites.

US usually shows breast cancer with mass lesions as hypoechoic masses. In this case, plain CT (figure 1B) and macroscopic findings of the resected specimen revealed that the breast cancer had a usual mass lesion. Therefore, if it were not for the silicone injection, the lesion was more likely to be palpable and appear as a hypoechoic mass. However, the lesion was not visualised as a hypoechoic mass. This may be due to the strong reflection, refraction, reverberation and attenuation of the ultrasonic beam resulting from fibrosis and silicon granulomas.1 In contrast, the FDG uptake site on PET/CT, that is, the site where the lesion was considered to be present, was carefully checked using CD to identify hypervascularisation. The extent of vascularisation in and around lesions is helpful in distinguishing between benign and malignant tumours.3 Although in this case, the site of FDG uptake was a non-mass lesion, a slightly hypoechoic area compared with the surrounding area, suggesting that a biopsy was required. This is the first report of breast cancer diagnosed through biopsy of a non-palpable, non-hypoechoic mass lesion with hypervascularisation after breast augmentation.

When a significant uptake of FDG is observed in the breast, the positive-predictive value for breast cancer is very high at 96.6%.4 Therefore, the lesion in this case was expected to be malignant. In contrast, FDG can also be taken up in case of acute and chronic inflammation, physiological lactation and benign localised breast masses, such as silicone granulomas, fat necrosis, fibroadenoma and postoperative changes.5 Several reports have shown that silicone granulomas show significant FDG uptake after breast augmentation,6 7 and FDG-uptake silicone granulomas were considered to be a differential diagnosis in this case. However, multiple non-vascular, hypoechoic masses without FDG uptake were also noted. In contrast, no hypoechoic mass was observed at the FDG uptake site. The hypoechoic masses seen were probably silicone granulomas, but to rule out breast cancer, an additional core needle biopsy was performed on one of the hypoechoic masses and were confirmed as silicone granulomas. Furthermore, the silicone granulomas in this case showed no vascularity; the absence of vascularisation suggests a non-malignant mass.8 Therefore, in patients who have undergone silicone injection, it is necessary to ensure that the site of core needle biopsy corresponds to the FDG uptake site. Without the accurate identification of the cancer site on US, only silicone granulomas can be diagnosed; the cancer site cannot be accurately biopsied, and the cancer cells may go undetected, especially in cases of non-palpable lesions.

Stereotactic-guided biopsy was reported to be useful for breast cancer diagnosis after breast augmentation with silicone injection when lesions are unidentifiable via US.9 It is common to not perform MMG after breast augmentation surgery due to quality control issues in screening for breast cancer and possible damage to the insertion. MMG findings are less likely to indicate mammographic abnormalities in the absence of any physical findings.8 However, while a history of silicone granulomas secondary to silicone injection may pose some difficulty, MMG cannot be considered ineffective. Therefore, for a quicker and more straightforward diagnosis, performing MMG should have been considered in this case. In addition, contrast-enhanced MMG may also have been effective for assessing breast vascularity in this case. Contrast-enhanced magnetic resonance imaging (MRI) may also be effective in detecting breast cancer after breast augmentation.10 However, even though the MRI findings strongly indicate the presence of cancer, a biopsy should be performed to confirm the diagnosis of cancer. Breast biopsy, most commonly performed under US guidance, is important to identify breast lesions on US. Although MRI-guided biopsies may be useful for diagnosing cancer after breast augmentation,11 this technique is only available in a limited number of facilities. In this case, because the lesion had already been identified on US, breast cancer was diagnosed using minimally invasive techniques.

In conclusion, CD should be actively used to detect hypervascularised areas to prevent false-negative biopsy results, especially when no lesions are detected on US. While CD was helpful in this case and is increasingly suggested as a relatively straightforward adjunct in complex and challenging cases, it may not be applicable to all cases; further research on its value is required. Breast augmentation with silicone injections is no longer performed and only the elderly has undergone this method in the past, however similar problems are expected to arise in case of silicone breast implant (SBI) injury. SBI is widely used for breast augmentation and breast reconstruction. In this case, breast cancer was incidentally found by PET/CT, but the lesion was initially non-palpable and asymptomatic, thus, making it difficult to detect breast cancer by US screening alone. Breast cancer screening using MMG may be required even after breast augmentation, but due care must be taken during the examination. Furthermore, PET/CT and MRI are not commonly used in screening for breast cancer, but these methods may be considered after breast augmentation, especially when lesions are not palpable or easily visible on US.