Answer:
A. Squamous papilloma (SP).
A. Squamous papilloma (SP). The squamous papilloma is a
very common benign epithelial lesion of the oral cavity,
induced by the human papilloma virus (HPV). There are at
least 150 types of the HPV virus.1 The most common types of
HPV involved in the pathogenesis of SP are types 6 and 11,
which have a low risk of transformation, low virulence, and
low infectivity rate.2 The exact mechanism of transmission has,
therefore, not been fully elucidated but may occur through
direct contact with another lesion. SP represents about 3
percent of all oral biopsies submitted, and occurs in one of
every 250 adults. It represents almost 7 percent of all oral soft
tissue growths in children.2 The lesion is common on the soft
palate and tongue, but can also develop on any mucosal
surface in the oral cavity, including the labial mucosa. It can
develop at any age and in any gender, although it is most
often seen in patients between the ages of 30-50 years.2
Clinically, SP presents as an asymptomatic, exophytic, pebbly,
rough, pedunculated mass or nodule with numerous papillary
projections. The papillary projections can be blunted or
pointed, which can give it a “wart-like” or “cauliflower-like”
appearance. The lesion is usually solitary, and its color may
range from normal mucosal color to slightly red or white in
appearance, depending on the amount of keratinization. The
lesion can exhibit rapid growth and ranges in size from 0.5
to upwards of 3.0 cm in diameter.2 Following the initial
growth phase, the lesion remains stable in size. Multiple
lesions associated with HPV can present in patients with
immunosuppression, such as post-transplant, HIV-associated,
or chemotherapeutic immunosuppression.3 The presence of
multiple SPs that coalesce may also be seen in certain skin
disorders and syndromes, such as acanthosis nigricans, Down
syndrome, and focal dermal hypoplasia. Another condition
caused by HPV types 6 and 11 is recurrent respiratory
papillomatosis (RRP).2 RRP can show extensive, and potentially
devastating, disease of the larynx and respiratory tract. RRP
can present in children (juvenile onset), often via infection
from the mother through the birth canal, amniotic fluid, or
placenta, or in adulthood (adult onset). This condition can
give rise to massive papillary growths in the respiratory tract
and can lead to difficulty breathing. Treatment is typically
based on symptoms, and the lesions often grow back after
surgical excision.
Histologically, SP demonstrates papillary projections of
parakeratinized stratified squamous epithelium with
fibrovascular connective tissue cores (Figure 2a and 2b).
Often noted is an increase in mitotic activity and hyperplasia
of the basal cell layer, which could be mistaken for mild
epithelial dysplasia.3 (Figure 3). Koilocytes (koilo-, hollow or
concave) are epithelial cells with pyknotic (darkly staining)
nuclei surrounded by a clear halo.2 They are often noted in
the spinous cell layer of the epithelium, and are seen in
approximately 50 percent of SPs.3 Koilocytes represent
HPV-infected epithelial cells. Truly atypical features, including
dysplasia and invasion, are worrisome for malignant
transformation, although this is rare.3 There is no convincing
association of SP with development of oral squamous cell
carcinoma.
Treatment involves conservative surgical excision, and
recurrence is unlikely. Given that SPs are the most common
papillary lesions to affect intraoral mucosa, and based
on the clinical manifestation of this lesion as a solitary,
pedunculated, exophytic lesion with finger-like projections,
a diagnosis of SP was favored in this case. However, a biopsy
was never performed and the patient was lost to follow-up.
Therefore, other possibilities cannot be fully excluded.
These are described below.
Figure 2A and 2B:
(H&E, 20x and 40x): Low and medium power views show an epithelial proliferation with papillary
projections.
Figure 3:
(H&E, 400x): A high power view shows epithelium
and vascular connective tissue cores. Increased
mitotic activity is noted in the basal cell layer,
a finding frequently noted in SP.
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