Differential Diagnosis for Callus vs Wart

When differentiating between a callus and a wart, it's essential to consider various diagnoses based on their likelihood and potential impact on patient health. The following categorization helps in systematically approaching this differential diagnosis:

• Single Most Likely Diagnosis

  • Callus: This is often the most likely diagnosis for a lesion that is caused by repeated friction or pressure on the skin, leading to thickening of the skin as a protective response. The location (commonly on hands or feet) and the absence of distinct borders or viral features can point towards a callus.
  • Wart: If the lesion has a characteristic cauliflower appearance, is located on the hands or feet, and has been present for a while, a wart (caused by the human papillomavirus, HPV) could be the single most likely diagnosis.

• Other Likely Diagnoses

  • Corn: Similar to a callus but typically smaller and more localized, often with a harder center. Corns can be tender to pressure and are usually found on the toes or feet.
  • Seborrheic Keratosis: A benign skin growth that can resemble a wart but is usually more pigmented and has a stuck-on appearance.
  • Molluscum Contagiosum: A viral infection that causes small, pearly, or flesh-colored bumps. The presence of a central depression (umbilication) can help differentiate it from warts.

• Do Not Miss Diagnoses

  • Squamous Cell Carcinoma (SCC): Although less common, SCC can sometimes be mistaken for a wart or callus, especially if it presents as a firm, rough-surfaced lesion. A history of sun exposure or immunosuppression increases the risk.
  • Melanoma: In rare cases, a melanoma can mimic a wart, especially if it is amelanotic (lacking pigment). Any new or changing skin lesion, especially one that is asymmetric, has irregular borders, color variation, a diameter greater than 6mm, or is evolving, should prompt concern for melanoma.

• Rare Diagnoses

  • Keratoacanthoma: A low-grade, or sometimes considered benign, tumor that can resemble a wart but typically grows more rapidly and has a central crater.
  • Verrucous Carcinoma: A rare, low-grade malignancy that can mimic a large wart, often found on the sole of the foot.
  • Epidermoid Cyst: While not typically confused with warts or calluses due to their cystic nature, they can sometimes present as firm, rough lesions if they become inflamed or infected.

Each of these diagnoses has distinct features and considerations, emphasizing the importance of a thorough clinical examination and, when necessary, diagnostic procedures like biopsies to ensure accurate diagnosis and appropriate management.