Answer: Keratosis oris (lichen
simplex chronicus of an oral mucous membrane)
Criteria for diagnosis
histopathologically: A slightly hyperplastic
epithelium with compact orthokeratosis, hypergranulosis, and a
sparse patchy infiltrate of lymphocytes and plasma cells in the
upper part of the lamina propria are changes of keratosis oris.
histopathologically: There is none.
Criteria for diagnosis clinically: A flat,
non-indurated plaque with a white, slightly papillated surface is
one presentation of keratosis oris.
Differential diagnosis clinically: Squamous
cell carcinoma or infection with Human papillomavirus (HPV) must be
ruled out by biopsy and evaluation of the specimen under the light
Clinicopathologic correlation: The white color
results from the abnormal production of cornified cells, and the
plaque is due to epithelial hyperplasia.
Options for therapy predicated on
knowledge of histopathologic findings: Since keratosis
oris results from chronic mechanical trauma, the lesion resolves
upon removal of the cause.
1) Keratosis oris is the mucous membrane
analogue of lichen simplex chronicus of the skin. Chronic
mechanical trauma is the common denominator in these two
conditions, and the characteristic features of hyperplasia, compact
orhtokeratosis, and hypergranulosis resolve after the cause is
2) A wide range of diseases may present as white plaques on
mucous membranes, including inflammatory diseases (lichen sclerosus
et atrophicus, lichen planus, lupus erythematosus, and psoriasis),
infections (candidiasis due to Candida albicans, hairy
leukoplakia due to Epstein-Barr virus, and HPV-induced lesions such
as warts), and neoplasms (squamous cell carcinoma).
3) Leukoplakia is an ill-defined term both clinically and
histopathologically. According to the definition by WHO,
"Leukoplakia is a whitish patch or plaque that cannot be
characterized clinically or pathologically as any other disease,
and is not associated with any physical or chemical causative
agent, except the use of tobacco." This definition implies that
leukoplakia is a diagnosis of exclusion: Only if no cause other
than tobacco smoking can be identified, the diagnosis is
leukoplakia. For pathologists, it is a meaningless term because no
specific histopathologic features are described.