Differential Diagnosis for the Patient's Condition

The patient presents with a pustule on the high cheek by the ear that has enlarged over the past 3 years, was once popped with blood, and is now raised, firm, and surrounded by a raised area. Here is a differential diagnosis organized into categories:

• Single Most Likely Diagnosis

  • Epidermoid Cyst: This is a common skin condition that can present as a firm, raised nodule, especially after being ruptured and then healing, which could lead to the formation of a firm, raised border around the original site. The history of the lesion being popped and then becoming more pronounced fits with the natural history of an epidermoid cyst that has become inflamed or infected.

• Other Likely Diagnoses

  • Infected Sebaceous Cyst: Similar to an epidermoid cyst but originating from sebaceous glands, these can become infected, leading to inflammation and a raised, firm appearance.
  • Furuncle or Carbuncle: A furuncle (boil) or carbuncle (a group of furuncles) could present as a raised, firm, and painful nodule, especially if the initial pustule became infected.
  • Pilomatricoma: A benign skin tumor that originates from the hair follicle matrix, which can present as a firm, raised nodule.

• Do Not Miss Diagnoses

  • Basal Cell Carcinoma: Although less likely, basal cell carcinoma can present as a firm, raised nodule, especially if it has been neglected or misdiagnosed. It's crucial to consider this diagnosis due to its potential for local destruction if left untreated.
  • Squamous Cell Carcinoma: Similar to basal cell carcinoma, squamous cell carcinoma can present as a firm, raised lesion, especially in sun-exposed areas like the cheek. It has a higher potential for metastasis than basal cell carcinoma.
  • Merkel Cell Carcinoma: A rare but aggressive skin cancer that can present as a firm, raised nodule, often with a history of rapid growth.

• Rare Diagnoses

  • Dermatofibrosarcoma protuberans (DFSP): A rare skin cancer that can present as a firm, raised nodule, often with a history of slow growth.
  • Metastatic Skin Nodule: In rare cases, a skin nodule could represent a metastasis from an internal malignancy, presenting as a firm, raised lesion.
  • Lymphoma Cutis: A rare condition where lymphoma presents in the skin, which could potentially mimic a firm, raised nodule.

Each of these diagnoses should be considered in the context of the patient's full history, physical examination, and potentially, diagnostic tests such as biopsy.