Squamous metaplasia of sebaceous gland.

Squamous metaplasia in the skin has been reported in the eccrine ducts as eccrine squamous syringometaplasia (ESS). To our knowledge, squamous metaplasia of sebaceous gland (SMSG) has not been described in human skin. Twenty-two biopsy specimens from patients with pressure lesions after cardiac surgery with extracorporeal circulation were evaluated for the presence of SMSG. Squamous metaplasia of sebaceous gland was identified in five of the eight scalp biopsies and none of the buttock biopsies. The squamous metaplasia began in the germinative outer layer and advanced in a centripetal way. We believe that SMSG is an unspecific change of the sebaceous cells secondary to a chronic injury. Ischemia appears to play a mayor role, but other factors such as chronic trauma or toxicosis can not be ruled out.