Imaging Case 26:
Breast cancer - Invasive Ductal Carcinoma after NACT
Breast-conserving surgery (BCS), combined with radiation therapy, is the standard treatment of choice for women with early-stage breast cancer. It offers survival rates equivalent to mastectomy while providing better cosmetic outcomes. Neoadjuvant chemotherapy (NACT) is commonly used in locally advanced and high-risk breast cancer cases, as it can improve long-term survival and allow for less aggressive surgery. By shrinking large tumors, NACT can make them operable or enable BCS instead of a mastectomy.
While NACT enhances surgical outcomes, it can also present challenges. For example, changes in tissue composition caused by chemotherapy can obscure the boundaries between the tumor and surrounding normal tissue, potentially complicating complete tumor removal with clear resection margins. This challenge underscores the importance of intraoperative margin assessment during BCS. Techniques such as specimen radiography and frozen section analysis are widely used, though each have limitations in accuracy, efficiency, or practicality [1].
Recent studies suggest that high-resolution specimen PET-CT imaging with FDG-based radiotracers provides a detailed view of resected breast tumor specimens, in a rapid and efficient manner [2,3]. This clinical case highlights how intraoperative specimen PET-CT imaging provides a clear, real-time visualization of the resected tissue, enabling surgeons to make well-informed decisions that may lead to better surgical outcomes.
This case is presented with the support of AZ Maria Middelares, Ghent, Belgium, and is part of the investigator driven study to explore potential indications of an intraoperative specimen PET-CT imager (Trial registration number: BUN: B0172022000009).
Patient history
A 55-year-old female was diagnosed with breast cancer in the right breast. Preoperative imaging showed a 30 mm tumor with no metastases. Biopsy confirmed Invasive Ductal Carcinoma, NST. Hormone receptor testing indicated ER and PR negativity, while HER2 was strongly positive (score 3+), with a Ki-67 proliferation index of 50%. The tumor was staged as T2N0M0. Given the tumor size and aggressiveness, she received six cycles of neoadjuvant chemotherapy (NACT). Post-NACT, the tumor shrank to approximately 10 mm, and breast-conserving surgery (BCS) with sentinel lymph node resection was planned.
Figure 1: Transverse, coronal, and sagittal slices of the specimen PET-CT images of the tumor specimen, together with a 3D view. Specimen orientation is as indicated. The PET tracer scale bar is depicted on the left-hand side. These images reveal increased 18F-FDG uptake at the inferior-anterior border of the specimen.
Specimen PET-CT imaging
The patient received an intramural injection of 99mTc for sentinel node localization, and was intravenously injected with 0.8 MBq/kg of 18F-FDG at the Nuclear Medicine Department. The patient was then transferred to the operating theatre and breast-conserving surgery was performed.
First the surgeon excised the tumor with the help of a magnetic seed. Clinical assessment of the margins was challenging since the breast was large and fatty. Immediately after resection, a high-resolution specimen PET-CT image was acquired in the operating theatre. Fig. 1 shows this image, showing increased 18F-FDG uptake at the anterior-inferior border, which indicates metabolically more active regions such as cancer cells. Based on this image, the surgeon decided to take a cavity shave in this area.
The sentinel lymph node was resected during the imaging time of the tumor specimen using a gamma probe. This tissue was placed in a specimen container and imaged using the AURA 10 specimen PET-CT scanner. The PET-CT images visualize a circular dense structure in which no significant 18F-FDG uptake is seen.
Figure 2: The (a) CT and (b) specimen PET-CT images of the sentinel lymph nodes. The PET tracer scale bar is depicted on the right-hand side. The CT images visualize a circular dense structure allowing confirmation that the lymph node was resected. The specimen PET-CT images of the lymph node showed no significant 18F-FDG uptake.
Table 1: Tumor and lymph node characteristics assessed by histopathological evaluation.
Histopathological evaluation
After PET-CT imaging, the surgical specimen was sent to the pathology department for routine histopathological evaluation, which was available after seven days. The histopathological results are listed in Table 1.
Final pathology showed that there was a positive surgical margin at the anterior side, in correlation with the highlighted 18F-FDG uptake seen on the specimen PET-CT images. The additional cavity shave yielded a final negative margin status. The patient could therefore immediately continue postoperative therapy, without the need for a reoperation.
Discussion and conclusion
In this case, the surgeon chose to perform an additional cavity shave based on the interpretation of the specimen PET-CT image as 18F-FDG uptake was reaching the anterior-inferior border of the specimen. Histopathological analysis confirmed tumor cells at this border, and the additional cavity shave successfully prevented the need for reoperation and its associated burden. Importantly, since the clinical assessment of the margins was challenging due to the size and structure of the breast, the AURA 10 specimen PET-CT imager provided critical information right at the point of surgery.
References
[1] St John et al. (2017). Diagnostic Accuracy of Intraoperative Techniques for Margin Assessment in Breast Cancer Surgery: A Meta-analysis. Ann Surg.
[2] Göker M. et al. (2020). 18F-FDG micro-PET/CT for intra-operative margin assessment during breast-conserving surgery. Acta Chirurgica Belgica. https://doi.org/10.1080/00015458.2020.1774163 ;
[3] Lambert B. et al. (2025) Feasibility study on the implementation of a mobile high-resolution PET/CT scanner for surgical specimens: exploring clinical applications and practical considerations. Eur J Nucl Med Mol Imaging. https://doi.org/10.1007/s00259-025-07143-z