A recent classification of adenomas of the breast included tubular adenoma. This uncommon lesion can be distinguished from fibroadenoma by the predominance of epithelium and relative lack of stroma. This is, to our knowledge, the first report of a tubular adenoma studied by aspiration cytology as well as light and electron microscopy. A 4-cm, slightly tender mass was found in the upper outer quadrant of the breast of a 26-year-old woman. Aspiration cytology showed abundant epithelial fragments, similar to those seen in fibroadenoma, but without the spindle cell component often seen in aspirates of that lesion. Light microscopic study of the excised mass showed a well-demarcated tumor of tubular glands and scanty stroma. By electron microscopy, the epithelial stromal junction was intact. This contrasts with the findings in fibroadenoma, and confirms that this difference can distinguish these lesions.