What characterizes a typical physical exam finding of a malignant breast mass?

A single nontender firm immobile mass is a classic characteristic of a malignant breast mass. In malignant breast tumors, the masses often exhibit a firm texture and lack of tenderness, distinguishing them from benign conditions. The immobility of the mass is attributed to the tumor's infiltration into surrounding tissues, which anchors it in place and makes it less likely to move upon palpation.

In contrast, benign breast conditions may present as soft and movable masses or tender nodules, which are less commonly associated with malignancy. Additionally, fluid-filled cysts are typically seen in benign situations and are characterized by their fluctuant nature. Cysts can often move freely under the skin and may be tender, whereas malignant masses generally present as more solid, fixed lesions. Thus, the presence of a firm, nontender, and immobile mass is a classic indication of a potential malignancy in the breast.