18F-fluorodeoxyglucose positron emission tomography/computed tomography findings of breast cancer with signet ring cell differentiation: A single-center experience

Abstract

Aim: Due to the low incidence of breast cancer with signet ring cell (SRC) differentiation, which constitutes less than 1% of all breast cancers, little is known about its imaging features. The aim of this study was to evaluate the utility of 18F-Fluorodeoxyglucose (18F-FDG) Positron Emission Tomography/Computed Tomography (PET/CT) in staging breast cancer with SRC differentiation. Methods: We conducted a retrospective analysis of 14 patients with histologically confirmed breast cancer with SRC differentiation who underwent 18F-FDG PET/CT at our institution between 2014 and 2023. The imaging findings were analyzed in terms of maximum standardized uptake value (SUVmax), lesion size, and the presence of regional or distant metastases were statistically evaluated. Results: The histological subtypes of SRC differentiated primary tumors were 9 invasive lobular, and 5 invasive ductal carcinoma. More intense 18F-FDG uptake was observed in primary tumoral lesions of the ductal subtype (mean SUVmax: 18.8±9.8; range: 2.6–28.9) compared to the lobular subtype (mean SUVmax: 2.6±1.3; range: 1.5–5.1) (p=0.007, Z=2.600). Among the patients included in the study, axillary lymph node metastasis was present in 64% (n=9) of the cases, with lymph node metastasis identified in five cases classified as ductal carcinoma. Additionally, distant organ metastasis was identified in 21% (n=3) of patients, comprising two patients with ductal carcinoma and one with lobular carcinoma. Conclusion: Despite the general consensus that signet-ring cell tumors have a low affinity for 18F-FDG, our study has observed the possibility of high 18F-FDG uptake in cases of ductal carcinoma. However, in cases of lobular carcinoma, where 18F-FDG uptake tends to be low, considering alternative PET radiopharmaceuticals for imaging could be a viable option.