We had previously reported a close association between pathological response and the maximum tumor standardized uptake value (SUVmax) measured by 18F-fluorodeoxyglucose positron emission tomography prior to chemotherapy in estrogen receptor (ER)-positive breast cancer. We hypothesized that glucose hypermetabolism by luminal B tumors may result in chemotherapy responsiveness. Using a single-gene expression assay, TargetPrint(R) (Agendia) and a 70-gene expression classifier, MammaPrint(R) (Agendia), we divided 20 patients with ER-positive primary breast cancer into luminal A and luminal B subtypes and compared the tumor SUVmax value between the two groups. A significantly higher SUVmax was measured for luminal B tumors (n=10; mean+/-SD, 7.6+/-5.6) than for luminal A tumors (n=10; mean+/-SD, 2.6+/-1.2; p=0.01). Glucose hypermetabolism could help predict intrinsic subtyping and chemotherapy responsiveness as a supplement to ER, progesterone receptor, HER2, and Ki-67 histochemical scores.