Ganglion cyst: This is the most common cause of a lump or swelling on the hand, particularly at the base of the fingers. Ganglion cysts are benign, fluid-filled lumps that can occur near joints or tendons, and they often present as non-painful swellings.

Dupuytren's contracture: Although typically associated with contracture of the palmar fascia, early stages can present with non-painful nodules or swellings at the base of the fingers, including the ring finger.
Heberden's nodes: These are bony spurs that occur due to osteoarthritis and can cause swelling at the base of the fingers, including the ring finger. They are more common in older adults.
Rheumatoid nodule: In patients with rheumatoid arthritis, nodules can form over bony prominences, including the base of the fingers, and may be non-painful.

Gout or pseudogout: Although these conditions are typically painful, in some cases, they can present with relatively mild symptoms, including non-painful swelling. Missing these diagnoses could lead to prolonged morbidity and potential joint damage.
Infection (e.g., abscess or cellulitis): While often painful, infections can occasionally present with minimal pain, especially in the early stages or in immunocompromised patients. Prompt diagnosis and treatment are crucial to prevent serious complications.
Malignancy (e.g., soft tissue sarcoma): Although rare, any unexplained swelling should prompt consideration of malignancy, as early detection significantly improves prognosis.

Giant cell tumor of the tendon sheath: A rare, benign tumor that can cause swelling around the fingers, including the base of the ring finger.
Lipoma: A benign fat tumor that can occur almost anywhere, including the hand, and might cause a non-painful swelling.
Neurofibroma: A benign nerve sheath tumor that can cause swelling and is associated with neurofibromatosis type 1 in some cases.