Small gland proliferations of the breast are a common source of diagnostic difficulty in breast pathology. Benign proliferations such as adenosis and radial scars can be mistaken for invasive carcinoma, and vice versa. Rare lesions such as low-grade adenosquamous carcinoma, microglandular adenosis, and adenomyoepithelioma are also predominately or entirely composed of small glands and may be mistaken for more common benign or malignant entities, with attendant differences in clinical management.  In this presentation, we will review the features of these challenging small gland proliferations, with an emphasis on key histologic findings, diagnostic pearls and pitfalls, and appropriate ancillary diagnostic studies.