This is the histology of a lesion removed 
  from the skin.

• What is the diagnosis?
  Answer
  Epidermal cyst. The histology shows a cyst 
  containing eosinophilic materials surrounded
  by epithelium. There are no dermal structures
  such as hair follicles or sebaceous glands seen.
   

  What may happen if the cyst is incompletely excised?

  a

  Answer
  The cyst may reform if the excision is incomplete.
  The content of the cyst may spill into the surrounding
  structures when the excision is incomplete or if the 
  wall is breached. This can lead to chronic inflammation with foreign body giant cells.