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Epidermoid Cyst (Inclusion Cyst)

- Discussion:
    - implantation of epithelioid tissues into deeper areas as a result of penetrating trauma;
          - often the inciting trauma occurs well into the past (patients may or may not remember);
    - mass is often mildly painful but is non tender, most often lies on the palmar skin of the hand or foot, often will not be perfectly round (rather bulboid) and is subcutaneous;
    - although, the mass may show some progressive growth, its chronic nature and well defined borders tend to suggest a beign lesion;
    - radiographs may show a cystic lesion;
    - diff dx:
          - ganglion cyst:
                - inclusion cyst will not transilluminate and will often not be perfectly round (as opposed to a ganglion cyst);
          - GCT of tendon sheath;
                - inclusion cysts will often not be located directly over flexor tendon sheaths, which may make the dx of GCT less likely;
          - fibroma;

- Management:
    - tumor mass is removed with care taken not to violate the outer pseudocapsule and with care taken to keep the skin flaps as thick as possible (in order to avoid necrosis);
    - once the mass is removed, the diagnosis is confirmed by cutting into the mass, which should reveal a thick greyish fluid

      - 70 yo male who noted a painless growth on the sole of his foot;
              - patient denied trauma to the foot