title: The white caruncle: sign of a keratinous cyst arising from a sebaceous gland duct.
abstract: OBJECTIVE
  To describe an acquired, smooth white lesion of the caruncle and to underscore the role of subsurface keratinizing squamous epithelium in its formation.
  
  
  METHODS
  Clinical photographic documentation, histopathologic evaluation, and immunohistochemical staining of an excised specimen from a 25-year-old woman.
  
  
  RESULTS
  A cyst was found that was lined by keratinizing squamous epithelium without a keratohyaline layer (trichilemmal keratinization), typical of lesions of the pilosebaceous unit. A portion of the cyst's lining was replaced by granulomatous inflammation resulting from an earlier spontaneous partial rupture. Ki-67 immunolabeling demonstrated relatively few nuclei in S-phase (DNA synthesis) in comparison with the overlying epithelium, thereby suggesting an obstructive, nonproliferative cause for the cyst.
  
  
  CONCLUSIONS
  A white caruncular lesion is a very rare finding according to the literature. It is most likely caused by a cyst lined by squamous epithelium elaborating trichilemmal-type keratin. A sebaceous gland duct was established as the source for the current lesion.
authors.affiliation: Department of Ophthalmology, David G. Cogan Laboratory of Ophthalmic Pathology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, 243 Charles Street, Boston, MA 02114, USA. Fred_Jakobiec@meei.harvard.edu
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Jakobiec
authors.forename: Manisha
authors.initials: M
authors.lastname: Mehta
authors.forename: Scott H
authors.initials: SH
authors.lastname: Greenstein
authors.forename: Kathryn
authors.initials: K
authors.lastname: Colby
mesh_terms: D000328:Adult; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D003560:Cysts / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D005141:Eyelid Diseases / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D007633:Keratins / Q000378:metabolism; D019394:Ki-67 Antigen / Q000378:metabolism; D009113:Muramidase / Q000378:metabolism; D012625:Sebaceous Gland Diseases / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D000097382:CD68 Molecule
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D007633:Keratins; D019394:Ki-67 Antigen; D009113:Muramidase; C067980:CD68 antigen, human; D000097382:CD68 Molecule