Differential Diagnosis for Raised Red Firm Lesions

• Single most likely diagnosis
  • Dermatofibroma: A common, benign skin growth that often appears as a firm, raised red lesion, typically resulting from minor injury, most often on the legs.
• Other Likely diagnoses
  • Keloid or Hypertrophic Scar: These are raised, firm lesions that can be red, resulting from an overactive healing process following skin injury.
  • Insect Bite or Sting Reaction: Some reactions to insect bites or stings can cause firm, red, raised lesions.
  • Keratoacanthoma: A low-grade, or sometimes considered benign, skin tumor that can appear as a firm, red, dome-shaped nodule.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Squamous Cell Carcinoma (SCC): Although less common than other skin cancers, SCC can present as a firm, red nodule and is crucial to diagnose early due to its potential for metastasis.
  • Basal Cell Carcinoma (BCC): The most common form of skin cancer, BCC can sometimes appear as a raised, red lesion, especially the nodular subtype.
  • Merkel Cell Carcinoma: A rare but highly aggressive skin cancer that can present as a firm, red nodule, often on sun-exposed areas.
• Rare diagnoses
  • Kaposi's Sarcoma: A rare cancer that can cause red, firm lesions on the skin, more commonly seen in immunocompromised individuals.
  • Angiosarcoma: A rare and aggressive cancer of the blood vessels that can appear as a red, firm lesion, often on the face or scalp.
  • Leukemia Cutis: In rare cases, leukemia can manifest in the skin as firm, red lesions due to the infiltration of leukemic cells.