JPC SYSTEMIC PATHOLOGY
Signalment (JPC #2233443): Age and breed unspecified dog
HISTORY: A slow growing neoplasm removed from the 2nd digit of the left forepaw
HISTOPATHOLOGIC DESCRIPTION: Haired skin, 2nd digit, left paw (per contributor): Expanding the dermis and elevating the mildly hyperplastic epidermis, is a well vascularized, pedunculated, 2.5 x 1 cm mass which contains few dysplastic and haphazardly arranged hair follicles and adnexa. The mass is composed of both loosely arranged and thick, tightly packed collagen bundles admixed with moderate numbers of reactive fibroblasts. Near the tip of the mass, collagen bundles are separated by clear space and lymphatics are ectatic (edema). Within the neck of the mass, perivascular connective tissue contains few scattered lymphocytes, plasma cells, macrophages and neutrophils. There is diffuse, mild, hyperkeratosis, acanthosis, spongiosis and short, rarely anastamosing rete ridges. Multifocally within the subjacent dermis, hair follicles and adnexa are surrounded by occasional lymphocytes, plasma cells, and macrophages.
MORPHOLOGIC DIAGNOSIS: Haired skin, 2nd digit, left forepaw (per contributor): Acrochordon, breed not specified, canine.
SYNONYMS: Fibroepithelial polyp, fibrovascular papilloma, skin tag, skin polyp
- Pedunculated to elongated proliferation of epidermis and dermal collagen
- Large and giant breeds may be predisposed, especially the Doberman pinscher and Labrador retriever
- Cause unknown
- May be a proliferative response to trauma or focal furunculosis
TYPICAL CLINICAL FINDINGS:
- Common sites include the trunk, sternum, and over bony prominences
- Middle-aged to old dogs
TYPICAL GROSS FINDINGS:
- Solitary or multiple, pedunculated, smooth or hyperkeratotic, soft mass that may be a few centimeters in length and up to 1 cm in width
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Dermis expanded by tightly packed collagen bundles
- Epidermis is acanthotic and hyperkeratotic
- Few or no adnexa
- Mild mononuclear inflammation may be present
- Fibroma: Well-circumscribed nodule composed of whorls and interlacing bundles of collagen and fibroblasts that compress adjacent tissue. Lacks inflammation and vascular proliferation
- Nodular dermatofibrosis: Multiple fibromatous nodules in German shepherd dogs associated with renal cystadenocarcinoma and uterine leiomyoma; poorly demarcated proliferation of dermal collagen, with epithelial hyperplasia and variable inflammation
- Collagen nevus (hamartoma): Poorly demarcated, exophytic proliferation of mature, haphazardly arranged collagen that may contain atrophied, entrapped adnexa
- Fibroadnexal dysplasia: Proliferation of mature dermal collagen, epidermal hyperplasia and disorderly proliferation of dysplastic adnexa
- Dermatofibroma: Proliferation of spindle to stellate fibrocytic cells arranged in haphazard bundles and small whorls, mixed with collagen bundles of varying thickness
- Single case of fibroepithelial hamartoma in the skin of a pig
- Brown PJ, Evans HK, et al. Fibroepithelial polyps of the vaginia in bitches: A historical and immunohistochemical study. J Comp Pathol. 2012; 147:181-185.
- Goldschmidt MH, Dunstan RW, Stannard AA, von Tscharner C, Walder EJ, Yager J. Histological Classification of Epithelial and Melanocytic Tumors of the Skin of Domestic Animals. Vol III. 2nd Series. Washington, DC:Armed Forces Institute of Pathology; 1998:36-37, 72.
- Gross TL, Ihrke PJ, Walder EJ, Affolter VK. Fibrous tumors. In: Skin Diseases of the Dog and Cat. Ames, IA:Blackwell Publishing; 2005:713-716.
- Scott DW, Miller WH, Griffin CE. Muller & Kirk's Small Animal Dermatology. 6th ed. Philadelphia, PA:WB Saunders Co; 2001:1284.
- Sipos W, Griessler F, Schilcher F, Stumpf I, Pirker E, Schmoll F. Fibroepithelial hamartoma in a domestic pig. Vet Pathol. 2007; 44(3):411-413.