Lipoma: A benign tumor composed of fat tissue, which can cause localized pain and numbness if it compresses nearby nerves. The location at the bend of the arm is a common site for lipomas to develop.

Cubital Tunnel Syndrome: This condition involves compression of the ulnar nerve at the elbow, leading to numbness, tingling, and pain in the arm and hand. The symptoms can be exacerbated by flexion of the elbow.
Elbow Bursitis: Inflammation of the bursae at the elbow can cause pain and swelling, potentially leading to increased subcutaneous fatty tissue appearance due to inflammation and fluid accumulation.
Radial Neuropathy: Compression or injury to the radial nerve can cause pain, numbness, and tingling in the back of the hand or the thumb side of the hand, potentially radiating to the elbow area.

Pancoast Tumor: A type of lung cancer located at the top of the lung, which can cause shoulder and arm pain, numbness, and tingling due to compression of nerves. Although rare, it is critical to consider due to its severe implications.
Thoracic Outlet Syndrome: Compression of the nerves and/or blood vessels that pass into the thoracic outlet (the space between your collarbone and first rib) can cause pain, numbness, and tingling in the arm, which could be mistaken for a localized elbow issue.

Multiple Hereditary Exostoses (MHE): A rare genetic disorder characterized by the growth of multiple bony spurs (exostoses) that can cause nerve compression and pain. While rare, it could potentially cause symptoms at the elbow.
Neurofibroma: A benign nerve sheath tumor that can cause pain, numbness, and tingling if it compresses nearby nerves. Neurofibromas can occur anywhere, including the arm, but are less common causes of the described symptoms.
Madelung's Disease: A rare condition characterized by the growth of abnormal fatty tissue around the neck and shoulders, which could potentially extend to the arm, causing localized pain and numbness due to nerve compression.