What finding would be concerning when palpating a lymph node in an adult?

When palpating a lymph node in an adult, a fixed and hard lymph node raises significant concern. This finding suggests that the lymph node could be involved in a pathological process, such as malignancy or an infectious disease. The characteristics of being hard and fixed indicate that the lymph node is not only enlarged but is also adhered to surrounding tissues. This adhesion can often denote a more serious underlying cause, such as cancer, which is typically associated with non-mobile lymph nodes due to tumor invasion into adjacent structures.

In contrast, soft and mobile lymph nodes are generally considered normal or reactive to benign processes, such as infections. Similarly, small and tender lymph nodes could indicate an acute inflammatory response, while a palpable and smooth lymph node generally signifies a benign or reactive state. Hence, the presence of a fixed and hard lymph node is a red flag that warrants further investigation, including imaging studies or potential biopsy, to rule out malignancy or other serious conditions.