Papilloma
(PAPILLOMATOSIS)
A benign exophytic neoplastic proliferation of the squamous epithelium caused by infection with a
papilomavirus.
The non-viral lesion has been classified as a squamous papilloma and may be found under tumor-like
lesions.
Gross Appearance:
Single or multiple finger-like projections of the epidermis
Histology:
•Epidermal hyperplasia
•Papillae supported by dermal fibrovascular stroma
•Capillaries are often prominent and dilated
•Overlying stratum corneum may exhibit hyperkeratosis or parakeratosis
•Granular layer is prominent
•Keratohyalin granules are often large, round or irregular
•Koilocytes (enlarged keratinocyte with eccentric pyknotic nuclei surrounded by wide clear
halos) may be seen in the spinous layer, and their "ghosts" in the stratum corneum
•Spinous layer is hyperplastic
•Normal eosinophilic cytoplasm is replaced by a pale basophilic cytoplasm (viral cytopathic effect)
•Cells may have intranuclear pale basophilic viral inclusions
•Occasionally, nuclei may contain small eosinophilic inclusions, and intracytoplasmic eosinophilic material which are not true viral
inclusions but aggregates of keratin
•Elongated rete at the periphery of the tumor are slanted towards the center
Prognosis:
Excellent. A very small percent of cases fail to regress and do
not respond to any therapy. These have more extensive oral involvement
than cutaneous involvement.
|
Sex Distribution (N=199)
|
| Sex |
Status |
Percent
|
|
|
|
26.1 |
|
|
17.6 |
|
|
|
25.1 |
|
|
31.2 |
(normal sex distribution)
| Anatomic Location (N=176) |
| Site |
Percent
|
| Head |
52.2 |
| Forelimb |
18.1 |
| Hindlimb |
10.8 |
| Multiple |
6.8 |
| Abdomen |
5.1 |
| Tail |
1.7 |
| Perineum |
1.7 |
| Neck |
1.2 |
| Thorax |
1.2 |
| Back |
1.2 |
| 
