Diagnostic impact of 18F-FDG PET/CT on the management of rare breast carcinomas: apocrine and neuroendocrine carcinomas

Abstract Objective We aimed to evaluate the diagnostic impact of 18 F-FDG PET/CT in staging apocrine breast carcinoma (ABC) and primary breast neuroendocrine carcinoma (PBNEC) and to demonstrate possible alterations of the 18 F-FDG uptake in these histopathologic subtypes. In addition, we aimed to compare 18 F-FDG PET/CT findings between ABC, PBNEC and invasive ductal carcinoma (IDC). Material and methods A total of 570 patients and 585 breast lesions were retrospectively included in this study. After patients were classified into molecular subtypes according to the histopathological analysis, 18 F-FDG PET/CT imaging was performed. The SUVmax findings of primary tumors obtained from 18 F-FDG PET/CT were compared between the groups. Results IDC was the most prevalent breast carcinoma (77.7%, n  = 446), with a low proportion of ABC (4.1%, n  = 24) and PBNEC (2.4%; n  = 14) diagnosed. The highest mean SUVmax was calculated in HER2 subtype of ABC and 18 F-FDG uptake ratio in HER2 and TN subtypes were found statistically higher than Luminal B type of ABC ( p  = 0.038 and p  = 0.019, respectively). Although 18 F-FDG uptake in Luminal B subtype of PBNEC was higher than Luminal A subtype, difference was not statistically significant. Additionally, the axillary metastasis rate was significantly higher in the ABC group ( p  = 0.015). Conclusions The histopathological ABC subtype group showed different 18 F-FDG uptake than the IDC group. Even if 18 F-FDG uptake was lower in the PBNEC group than in the other groups, PET/CT showed and adequate performance in detecting primary tumors and metastases. The 18 F-FDG PET/CT scan results may contribute to the initial staging and management of ABC and PBNEC patients.