If a mass feels mobile in both directions, what is it most likely to be?

When a mass feels mobile in both directions, it is most indicative of a lymph node. Lymph nodes are typically more mobile because they are not fixed to underlying structures. They can be palpated as discrete, soft, and sometimes rubbery entities that move easily over the surrounding tissues.

In contrast, masses that are fixed or less mobile often suggest malignancy such as cancer, which tends to adhere to surrounding tissues and structures. Infected cysts might also feel somewhat mobile but often present with associated tenderness or signs of infection, which distinguishes them from lymph nodes. Fatty tissue, while also mobile, tends not to present as a discrete mass and is generally soft and non-tender without the defined borders typically associated with lymph nodes.

Thus, the mobility in both directions is a hallmark characteristic that aligns with the nature of lymph nodes, making it the most likely answer for this scenario.