68Ga–Prostate-Specific Membrane Antigen PET/CT and 18F-FDG PET/CT of Primary Signet Ring Cell Breast AdenocarcinomaParihar, Ashwin Singh, MBBS*; Mittal, Bhagwant Rai, MD, DNB*; Sood, Apurva, MD*; Basher, Rajender Kumar, MD*; Singh, Gurpreet, MS†Clinical Nuclear Medicine: November 2018 - Volume 43 - Issue 11 - p e414–e416 doi: 10.1097/RLU.0000000000002265 Interesting Images Abstract Author InformationAuthors Article MetricsMetrics Primary signet ring cell adenocarcinoma of the breast is a rare neoplasm. Similar to other mucinous neoplasms, it has low FDG avidity and poor prognosis compared with the traditional ductal/lobular carcinomas. We present a case of a 40-year-old woman with signet ring cell adenocarcinoma and skeletal fluorosis showing higher uptake of 68Ga–prostate-specific membrane antigen in the primary lesion and the metastatic sites compared with 18F-FDG on PET/CT imaging. Additionally, diffuse increased prostate-specific membrane antigen uptake was noticed in the entire skeleton, likely due to skeletal fluorosis. From the *Department of Nuclear Medicine & PET and †General Surgery Post Graduate Institute of Medical Education and Research, Chandigarh, India. Received for publication June 9, 2018; revision accepted July 22, 2018. Conflicts of interest and sources of funding: none declared. Correspondence to: Bhagwant Rai Mittal, MD, DNB, Department of Nuclear Medicine, Post Graduate Institute of Medical Education and Research, Chandigarh 160012, India. E-mail: firstname.lastname@example.org. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.