Hematopoietically Active Adrenal Myelolipoma Mimicking Breast Cancer Metastasis

A 66-year old woman had a left breast mass. Biopsy showed invasive ductal carcinoma. A PET/CT scan demonstrated hypermetabolism in the left breast and atypical heterogeneously increased uptake throughout the skeleton as well as a minimally FDG-avid right adrenal myelolipoma. PET/CT 4 months later after 6 cycles of neoadjuvant chemotherapy demonstrated increased size and FDG avidity of this adrenal mass concerning for metastasis and uniformly increased skeletal FDG avidity. Biopsy demonstrated adrenal myelolipoma. The growth and increased FDG avidity of the adrenal myelolipoma were due to the action of colony-stimulating factors on the tumor's hematopoietic component.