A 62-year-old man presented because he was very concerned about the sudden appearance and rapid growth of a raised lump on his forehead. It started as a small red lump but over the past three to four weeks has grown to a diameter of 2cm. It is painless and he is otherwise well.
On examination, there is a 2cm raised lesion with a central crater surrounded by a heaped shoulder with normal adjacent skin. There is no lymphadenopathy.
What is the diagnosis, management and differential diagnoses?
Diagnosis and management
The lesion is a keratoacanthoma - a fast-growing skin tumour deriving from pilosebaceous glands on sun-exposed areas of skin. This is a common tumour occurring in one in 1,000 with a male-to-female ratio of 2:1. It tends to occur on the face, neck, hands and forearms. Possible causes include sun exposure, trauma, viral infection and chronic exposure to tar or petroleum.
Keratoacanthomas grow rapidly over four to 10 weeks, reaching 1-3cm before remaining static in size. They involute over two to three months leaving an unsightly irregular scar if left untreated. Treatment is usually with surgical excision. Small lesions may be treated with cryotherapy. Radiotherapy is effective but rarely used.
Possible differential diagnoses
- Squamous cell carcinoma - diagnosis of exclusion.
- Actinic keratoses.
- Basal cell carcinoma.
Squamous cell carcinoma
- Invasive or in situ.
- Usually caused by excessive sun exposure.
- Develops in a long-standing actinic keratosis.
- Does not usually metastasise with the exception of lip or ear lesions.