Wilcox et al (2019) reported on 193 dogs with squamous cell carcinoma.
Dermal only – not nail or elsewhere
54% were in predisposed areas, 46% were in nonpredisposed areas – periarticular, ventral neck, perianal.
White coat – 56%
5 dogs were hypercalcemic
39% had actinic change, 47% had no actinic change,
60% invasive, 11% noninvasive
13% had lymphovascular invasion
3 cases had papillomavirus evidence
22% metastasis 15% at presentation (Lymph node 9% and lung 6%) 7% developed mets later – Ln, Lung and 3 dogs elsewhere.Cunha et al (2023) reported on 54 cases and metastasis was in 34%.
Dos Santos et al (2023) reported on metastasis in 12 of 309 cases (4%). Most were on the abdomen.
Willcox JL, Marks SL, Ueda Y, Skorupski KA. Clinical features and outcome of dermal squamous cell carcinoma in 193 dogs (1987-2017). Vet Comp Oncol. 2019 Jun;17(2):130-138.
Dos Santos A, Lamego ÉC, Eisenhardt LM, et al. Prevalence and anatomopathological characterization of cutaneous squamous cell carcinomas with regional and distant metastases in dogs and cats: 20 cases (1985-2020). Vet Comp Oncol. 2023; 21: 291-301.
Weiner (2021) wrote a review of the follicular tumors in dogs. This review provides and excellent overview of the hair follicle and tumors that develop in dogs.
Selected those with reserve cells >50% of population
30 cases
Peripheral invasion 9 cases
5 cases intravascular invasion
3 systemic metastasis all had peripheral invasion, intravascular emboli and MI >50.S. Sabattini, P. Bassi and G. Bettini. Histopathological Findings and Proliferative Activity of Canine Sebaceous Gland Tumours with a Predominant Reserve Cell Population. J Comp Path 152: 145-152.
Immunohistochemically, the tumor cells were intensely positive for cytokeratin 7 and 20 and negative for S100 protein.
In the normal skin, co-expression of CK8/18 was found in the glandular epithelium of apocrine sweat glands, and single CK8-immunoreactivity was detected occasionally in the external root sheath at the isthmus and suprabulbar regions of the hair follicles. Sebaceous glands negative
Simko E, Wilcock BP, Yager JA. A retrospective study of 44 canine apocrine sweat gland adenocarcinomas. Can Vet J. 2003 Jan;44(1):38-42. PMID: 12619554; PMCID: PMC340017.
44 cases
followup on 25
5 of 44 invaded vessels
1 of 25 metastasized
Schulman, Lipscomb, Aitkin JVDI 17: 403-411
26 dogs
clear cell morphology
DDX balloon melanoma, sebaceous carcinoma
PAS positive
Oil red o negative
Cytokeratin + (29 of 29)
Vimentin + (29 of 29)
S100 + (24 of 29)
Melan A + (8 of 12)
SMA –
Some have cartilage
22 had some follicular differentiation
3 had metsIn a case reported by Sakuma et al (2010) neoplastic cells were positive for pan-cytokeratin (CK) (AE1/AE3 and CAM5.2), CK8 and CK18, but negative for pan-CK (KL1), CK7, CK14, CK16 and CK20. They are also double positive vimentin and cytokeratin.
Sakuma A, Nishiyama S, Yasuno K, Ohmuro T, Kamiie J, Shirota K. A case of canine cutaneous clear cell adnexal carcinoma with prominent expression of smooth muscle actin. J Toxicol Pathol. 2010; 23: 265-269.
Schulman FY, Lipscomb TP, Atkin TJ. Canine cutaneous clear cell adnexal carcinoma: histopathology, immunohistochemistry, and biologic behavior of 26 cases. J Vet Diagn Invest. 2005; 17: 403-411.
Yasuno K, Nishiyama S, Suetsugu F, Ogihara K, Madarake H, Shirota K. Cutaneous clear cell adnexal carcinoma in a dog: special reference to cytokeratin expression. J Vet Med Sci. 2009; 71: 1513-1517.
This is a synomym for clear cell adnexal carcinoma
Mikaelian and Wong reported 30 cases. All cases were PAS positive for glycogen, and the cells are CK (AE1/AE3) + and vimentin + in 29
4 of 8 had metastases to the local lymph nodesMikaelian I, Wong V. "Follicular stem cell carcinoma: histologic, immunohistochemical, ultrastructural, and clinical characterization in 30 days". Vet Pathol. 2004; 41: 302.
eccrine syringofibroadenoma.