Differential Diagnosis for Small White Lump on Arm that Hurts when Touched
- Single most likely diagnosis
- Cyst (e.g., epidermoid or sebaceous cyst): A common, benign lump that can appear on the skin, often filled with a cheesy or oily material, and can become inflamed or infected, causing pain when touched.
- Other Likely diagnoses
- Abscess: A collection of pus that has built up within the tissue of the body, indicating a local infection, which can cause a painful lump.
- Boil (Furuncle): A skin infection of a hair follicle that can cause a painful, pus-filled lump, typically appearing as a small, white or red bump.
- Ingrown Hair: A condition where a hair grows back into the skin, causing inflammation, redness, and sometimes a small, painful lump.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Skin Cancer (e.g., basal cell or squamous cell carcinoma): Although less common, it's crucial to consider skin cancer, as some types can present as a small, painful lump, and early detection is vital for effective treatment.
- Necrotizing Fasciitis: A rare but severe infection that can cause pain, swelling, and skin lesions, which can rapidly progress and be life-threatening if not promptly treated.
- Rare diagnoses
- Dermatofibroma: A rare, benign skin growth that can appear as a small, hard lump, often after a minor injury, and may be painful when touched.
- Lipoma: A rare, benign tumor composed of fat tissue that can appear as a small, movable lump under the skin, which may cause pain if it presses on nearby nerves or tissues.
- Pilar Cyst: A rare, benign cyst that originates from the hair follicle and can appear as a small, white or flesh-colored lump, which may become inflamed or infected, causing pain.