Differential Diagnosis for a Mobile Lump in the Shoulder Area

• Single Most Likely Diagnosis
  • Lipoma: A benign tumor composed of fat tissue, lipomas are common and can occur anywhere in the body, including the shoulder area. They are typically mobile, soft, and painless.
• Other Likely Diagnoses
  • Cyst: Such as a sebaceous cyst, which is a benign, usually mobile, lump under the skin that can occur in the shoulder area.
  • Abscess: A collection of pus that has built up within the tissue of the body, indicating a local infection. It can be mobile if not deeply embedded.
  • Hematoma: A collection of blood outside of blood vessels, which can feel like a lump and may be mobile, depending on its location and the stage of healing.
• Do Not Miss Diagnoses
  • Soft tissue sarcoma: Although rare, sarcomas can present as a lump in the shoulder area. Early detection is crucial for treatment outcomes, making it a "do not miss" diagnosis.
  • Infected or inflamed lymph node: While less common in the shoulder area compared to the neck or armpits, an infected lymph node could present as a mobile lump and indicates an underlying infection or potentially more serious condition.
• Rare Diagnoses
  • Dermatofibrosarcoma protuberans (DFSP): A rare type of skin cancer that can appear as a lump, often in the shoulder or chest area. It is typically mobile and can grow slowly over years.
  • Metastatic tumor: In rare cases, a lump in the shoulder area could be a metastasis from a cancer elsewhere in the body, though this would be uncommon without a known primary cancer.