In this lecture, we review a comprehensive FDG PET/CT evaluation of a 63-year-old female with invasive ductal carcinoma, no special subtype, characterized by an ER-positive, PR-positive, HER2-negative profile and a low Ki-67 proliferative index. The case illustrates how metabolic imaging integrates with histopathology and molecular subtype to guide interpretation, staging, and diagnostic confidence.
The discussion walks through the systematic assessment of the primary breast mass, regional nodal stations, internal mammary chain, supraclavicular fossa, pulmonary nodules, and osseous lesions. Emphasis is placed on correlating CT morphology with metabolic activity, applying level-based axillary nodal anatomy, recognizing characteristic patterns of metastatic spread, and understanding how molecular phenotype, particularly a luminal A profile, modulates expected FDG uptake and affects the diagnostic threshold for calling nodal disease.
The lecture underscores the importance of incorporating tumor biology into PET interpretation, recognizing subtle nodal uptake in low-FDG phenotypes, and adhering to structured, reproducible criteria for measuring nodes, defining levels, and distinguishing benign from suspicious findings.

Learning Objectives:

By the end of this lecture, participants will be able to:

• Characterize the primary breast lesion on PET/CT, including margins, internal architecture, metabolic intensity, and dermal involvement.
• Apply axillary, internal mammary, and supraclavicular nodal level criteria and integrate size and uptake thresholds to assess metastatic involvement.
• Identify common metastatic patterns in invasive ductal carcinoma, particularly pulmonary nodules and lytic bone lesions with corresponding metabolic activity.
• Incorporate molecular subtype information—including ER/PR/HER2 status and Ki-67—to anticipate FDG uptake patterns and refine interpretation of equivocal nodes.
• Determine staging implications (T, N, M) based on PET/CT findings and understand when additional imaging, such as brain MRI, is warranted.