Mucous cyst: This is the most common type of cyst found on the DIP (distal interphalangeal) joint of the finger. It is usually filled with a clear, jelly-like fluid and is often associated with osteoarthritis. The cyst can cause discomfort and may lead to nail plate deformity if it becomes large enough.

Ganglion cyst: Although more commonly found on the wrist, ganglion cysts can also occur on the fingers, including the DIP joint. They are benign lumps filled with a jelly-like fluid and can cause pain, especially if they press on a nerve.
Epidermoid cyst: These cysts are benign and can occur anywhere on the skin, including the fingers. They are usually filled with a cheesy material and can become inflamed if infected.
Sebaceous cyst: Similar to epidermoid cysts, sebaceous cysts are benign and can occur on the fingers. They originate from the sebaceous glands and can become inflamed.

Squamous cell carcinoma: Although rare, any lump or cyst on the skin should be evaluated for the possibility of skin cancer, including squamous cell carcinoma. This type of cancer can present as a firm, growing nodule.
Infectious abscess: An abscess on the finger can present similarly to a cyst but is usually painful, red, and warm to the touch. It requires prompt antibiotic treatment or drainage.
Osteomyelitis or septic arthritis: Infection of the bone (osteomyelitis) or joint (septic arthritis) can present with swelling and pain in the affected area, including the DIP joint. These conditions are medical emergencies.

Glomus tumor: A rare, benign tumor that usually occurs under the fingernail. It can cause pain, especially to pressure or cold temperatures.
Digital myxoid cyst: Similar to a mucous cyst but less common and filled with a gelatinous material. It can be associated with osteoarthritis.
Synovial cyst: A rare type of cyst that can occur over the DIP joint, filled with synovial fluid. It is usually associated with rheumatoid arthritis or other inflammatory conditions.