Final answer:
For a 14-year-old male with a firm area under the areola, observation is typically appropriate as it can be normal during puberty, but evaluation by a healthcare provider is recommended to rule out other possibilities.
Step-by-step explanation:
The appropriate action to take for a 14-year-old male with a slightly tender 2-cm area of concentric firm mobile tissue under the left areola is likely monitoring the situation, as this can be a normal part of adolescent development. During puberty, hormonal changes can lead to benign breast development in males, a condition known as gynecomastia, which often resolves on its own. However, it is advisable for the individual to see a healthcare provider to rule out other potential concerns and to confirm that this is indeed a normal part of development. The provider might conduct a physical examination and possibly suggest a period of observation to monitor for changes such as the area becoming larger, more tender, or exhibiting other symptoms that could suggest a different diagnosis.