Lisa Gordon
Animal Health Laboratory, University of Guelph, Guelph, ON.
AHL Newsletter 2025;29(1):13.
An adult Nubian goat was presented for a pedunculated mass just lateral to the anus that had reportedly arisen in the previous 36 hours. An excisional biopsy was performed, and the tissue was submitted for histological examination. An exophytic, pedunculated mass arose from the dermis at junction of haired and unhaired skin (Fig. 1). The mass was comprised of a central, fibrous tissue stromal core surrounded by multiple lobules of polygonal cells arranged in packets with rare, interspersed tubules or ducts that contained deeply eosinophilic fluid with scattered clear vacuoles. The epithelial cells had variably distinct cell borders and scant to abundant eosinophilic cytoplasm. Many of the cells exhibited basal cell differentiation, but some of the cells exhibited sebocyte-type differentiation (Fig. 2A). Approximately 60% of the mass was necrotic and included scattered neutrophils and abundant hemorrhage (Fig. 2B). The surface of the mass was ulcerated and coated with a serocellular crust containing scattered degenerate neutrophils and numerous colonies of basophilic coccoid bacteria (Fig. 2C). The mass was diagnosed as a suspect sebaceous epithelioma.
Caprine neoplasia is uncommon, with lymphoma, melanoma, fibropapilloma, squamous cell carcinoma, thymoma, and nasal carcinoma amongst the more common entities diagnosed. There are a few reports of sebaceous neoplasms in goats, usually sebaceous epitheliomas (two of which were also located in the perianal region), but prognostic information was not included. In general, sebaceous epitheliomas in cats and dogs are often cured by excision with adequate surgical margins. A few of these masses (in small animals) can metastasize to local lymph nodes - usually neoplasms excised from the head - but the prevalence of metastasis in goats is unknown.
Over the last 10 years at the AHL, 57 caprine cases have been submitted in which at least one skin condition was diagnosed (Fig. 3). The most common diagnosis was non-specific, often eosinophilic or neutrophilic dermatitis with hyperkeratosis (n=22); some of these cases were compounded by a superficial bacterial pyoderma. Differential diagnoses include ectoparasitism or ectoparasite hypersensitivity, bacterial dermatitis, Malassezia infection, zinc-responsive dermatopathy, or vitamin E/selenium deficiency. In rare cases with similar lesions, a specific cause was diagnosed: zinc deficiency in a goat with low serum zinc levels (0.44 ug/mL, ref: 0.65-2.7 ug/m); and Malassezia infection or mange in animals with intralesional organisms. However, follow-up testing and bloodwork were rarely available in a majority of cases. The second most common diagnosis (n = 12) was pediculosis (louse infestation), and these were all recorded in animals submitted for postmortem examination that were usually emaciated with concurrent debilitating disease. Bacterial dermatitis and necrotic/ulcerative skin lesions were diagnosed in 9 and 5 animals, respectively. Four cases of proliferative lesions were diagnosed in the past 10 years, including the previously described epithelioma along with a single case each of fibroma, squamous cell carcinoma in situ, and squamous papilloma. Abscesses, dermatophytosis, mange, cutaneous cyst, hematoma, Malassezia infection, hyperkeratosis, zinc deficiency dermatopathy and a laceration were diagnosed in three or fewer cases. Based on these described cases and the reviewed literature, neoplasia, abscess, cyst, granuloma, hamartoma, seroma, and hematoma are all reasonable differential diagnoses for cutaneous masses in goats. Cytology and/or histology may be required for definitive diagnosis.
Figure 1. Perineum. An exophytic, pedunculated mass arises from the dermis at junction of haired and unhaired skin. Subgross, H&E stain.
Figure 2. Dermis, perineum. H&E stain. 2A. Most of the tumour cells exhibit basal cell differentiation (thin arrow), but some of the cells exhibit sebocyte-type differentiation (thick arrow). 40X. 2B. Approximately 60% of the mass is necrotic and includes scattered neutrophils and abundant hemorrhage (asterisk). 10X. 2C. The surface of the mass is ulcerated and coated with a serocellular crust with scattered degenerate neutrophils, and numerous colonies of basophilic coccoid bacteria (thin arrow). 10X.
Figure 3. A total of 67 skin conditions were diagnosed in 57 caprine submissions from January 1, 2015 to December 31, 2024. Diagnoses with two or more recorded cases in this period are shown in the bar graph. Only a single case of each of the following conditions was recorded, so they were not included in the figure: cutaneous cyst, hematoma, Malassezia infection, hyperkeratosis, zinc deficiency dermatopathy and a laceration.
References
1. Löhr CV. One hundred two tumors in 100 goats (1987–2011). Vet Pathol 2013;50(4):668-675. doi:10.1177/0300985812471544.
2. Howerth EW, Butler A. Survey of goat tumors, Department of Pathology and Athens Veterinary Diagnostic Laboratory, College of Veterinary Medicine, UGA, from 2007–2011. Vet Pathol 2011;48(6):E21.
3. Brandly PJ, Migaki G. Types of tumors found by federal meat inspectors in an eight-year survey. Ann N Y Acad Sci 1963;108(3):872-879.
4. Kiser PK, Löhr CV. Lymphoma classification in goats. Vet Pathol 2017;54(4):611-619.