Quiz 9: What is your diagnosis?

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Diagnosis: Quiz 9

Quiz 9

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.

Differential diagnosis 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 microscope.

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 removed.

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.

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