Single Most Likely Diagnosis
- Hematoma: This is the most likely diagnosis given the history of blunt trauma to the head. A hematoma is a collection of blood outside of blood vessels, which can cause a firm lump beneath the skin surface.
Other Likely Diagnoses
- Subcutaneous abscess: Although less common in the immediate aftermath of trauma, if the wound became infected, an abscess could form, presenting as a firm, painful lump.
- Lipoma or other benign skin growths: If the lump was present before the trauma and the patient only noticed it after the incident, it could be a pre-existing condition like a lipoma.
Do Not Miss Diagnoses
- Subdural or epidural hematoma: These are life-threatening conditions that can occur after a head injury. Although they might not directly cause a palpable lump beneath the skin, they can cause symptoms that might lead to a misdiagnosis if not considered.
- Skull fracture: A fracture could lead to a collection of blood or other fluid that might feel like a lump, and it's crucial to identify and treat promptly to avoid complications.
Rare Diagnoses
- Osteoma or other bony growths: These could potentially cause a firm lump, especially if the trauma caused a fracture that led to abnormal bone growth.
- Soft tissue sarcoma: Although extremely rare and unlikely to be directly related to the trauma, any unexplained lump should prompt consideration of malignancy, especially if it persists or grows over time.