A spiculated mass is a centrally dense lesion seen on mammography with sharp lines radiating from its margin. The spicules can vary greatly in length, from a few millimeters to several centimeters. In malignant lesions, spicules represent a mixture of tumor cells and fibrosis invading the normal tissue surrounding the lesion. Although a spiculated mass is thought of as a classic finding of malignancy on mammography, ultrasound, and MRI, its differential diagnosis includes benign lesions. However, unless clinical history strongly supports a benign diagnosis, a spiculated mass on any modality typically will require additional workup and biopsy. This chapter reviews the key imaging and clinical features, imaging protocols and pitfalls, differential diagnoses, radiology–pathology correlations, and clinical management recommendations for a spiculated mass. Topics discussed include both malignant and benign masses.