Incidental [68Ga]Ga-DOTATATE uptake in bone metastases of breast carcinoma in a patient with a secondary carcinoid tumor

Background Lobular breast cancer often shows only low [ 18 F]FDG uptake, limiting the sensitivity to detect metastases. Alternative tracers, targeting tumor activated fibroblasts or estrogen receptors, can offer higher accuracy. Also, Somatostatin Receptor 2 (SSTR2) is significantly expressed in some breast cancers, particularly in estrogen receptor rich tumors. Typical pulmonary carcinoids also have low [ 18 F]FDG accumulation, but approximately 63% of well-differentiated lesions express SSTR2. Case presentation We report the case of a 66-year-old female patient with lobular breast cancer and a coincidentally discovered typical carcinoid of the lung. On subsequent [ 68 Ga]Ga-DOTATATE PET/CT to stage the carcinoid tumor, two SSTR2 positive focal lesions in the bones were present, without [ 18 F]FDG uptake but with mild sclerosis, atypical for metastasis of carcinoids. Biopsy confirmed osseous breast cancer metastases. Conclusion SSTR2 expression in normal breast tissue and breast carcinoma has been described previously. However, the case underscores the importance of awareness of atypical presentations of cancer within a multi-tracer approach, whereby receptor profile and morphology must be carefully integrated.