Squamous Papilloma

Squamous papilloma is a hyperplastic proliferation of squamous epithelium and is a member of the family of mucocutaneous lesions that includes verrucous vulgaris and condyloma acuminatum. They are thought to be caused by the human papilloma-virus (HPV), a large and growing family of viruses with more than 90 subtypes. No single member of this family is constantly associated with oral papillomas. HPV types 1, 2, 4, 6, 7, 11, 13, 16, 32, 57, 72, and 73 have been identified in oral papillomas and the virus is found in approximately 13% of specimens of normal oral mucosa. The ability to find the virus and identify the subtype may be related to the experience, skill, and tools of the clinician. The virus infects basal keratinocytes, and the portal of entry is created by a breach in the epithelial barrier. It is believed that the virus attaches to cell surface integrins and is internalized by endocytosis of the integrin-virus complex. Viral proteins E6 and E7 disable cellular proteins p53 and retinoblastoma (rb), respectively. Inactivation of these two important regulators of the cell cycle permits cells to pass through the Gl checkpoint unchallenged. Oral papillomas are commonly referred to as epithelial tumors but their behavior is that of a hyperplastic, not neoplastic lesion. Clinically they appear as exophytic, verrucous, or papillary lesions that are ordinarily a few millimeters in size. They lesions may be broad-based and sessile with a histomorphology is characterized by fronds of squamous epithelium, each with a core of edematous connective tissue. Increased numbers of mitoses are encountered but they are of normal morphology. Koilocytes are generally absent. The treatment is elective surgical removal and recurrences are rare. Oral squamous papillomas are associated with low-risk HPV and they do not undergo malignant transformation.

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