Breed predisposition to squamous cell carcinoma of the nail bed and digit, described in the Poodle (especially the dark-coated Standard Poodle) and the Giant Schnauzer, among other large, dark-coated breeds. The tumour destroys the nail and the distal phalanx and causes lameness. Metastasis is uncommon (around 4 % at 5 years; Chiu et al. 2022), although it may appear in a lymph node or lung in isolated cases. The association with dark coat suggests a genetic component linked to pigmentation.

The Standard Poodle (especially dark-coated) and the Giant Schnauzer present a much higher risk than the general dog population (Giant Schnauzer OR ≈57; black Standard Poodle OR ≈11; Chiu et al. 2022, PMID 36325409). In Standard Poodles and Giant Schnauzers, around 56 % develop tumours in other digits. Exact frequencies are not published; age, trauma and environment influence presentation.

- Lameness of one digit\n- Swelling and pain of the affected digit\n- Loss or deformity of the nail\n- Ulcerated or proliferative lesion of the nail bed\n- Pathological fracture of the phalanx\n- Possible involvement of several digits successively

The predisposition to ungual carcinoma of the black Standard Poodle and the black Giant Schnauzer was documented in retrospective veterinary oncology series. A higher incidence was observed in dark-coated dogs compared with light-coated dogs of the same breed, which pointed to a genetic component related to pigmentation. No single causative mutation has been characterised; the genetic test is understood as a breed risk marker, not as a diagnostic test.

- This is not a classic carrier test: the result guides on risk, not on guaranteed affected offspring\n- Avoid breeding dogs with a personal or family history of ungual carcinoma\n- Monitor for the appearance of nail lesions in risk lines and refer to the veterinarian early\n- Do not mate two dogs with a history of tumours of the nail bed

The differential diagnosis includes ungual infections (bacterial, fungal), trauma and other digital tumours (melanoma, soft tissue sarcoma, nerve sheath tumour). Confirmation is histopathological after digit amputation or biopsy. Radiography of the digit assesses bone destruction; staging includes chest and lymph nodes. The treatment of choice is digit amputation.

1. Chiu O, Wilcock BP, Wilcock AE, Edwards AM. (2022) Breed predilections and prognosis for subungual squamous cell carcinoma in dogs. Can Vet J 63:1129-1134. PMID: 36325409
2. Karyadi DM, Karlins E, Decker B, et al. (2013) A copy number variant at the KITLG locus likely confers risk for canine squamous cell carcinoma of the digit. PLoS Genet 9:e1003409. PMID: 23555311
3. O'Brien MG, Berg J, Engler SJ. (1992) Treatment by digital amputation of subungual squamous cell carcinoma in dogs: 21 cases (1987-1988). J Am Vet Med Assoc 201:759-761. PMID: 1399782
4. Belluco S, Brisebard E, Watrelot D, et al. (2013) Digital squamous cell carcinoma in dogs: epidemiological, histological, and immunohistochemical study. Vet Pathol 50:1078-1082. PMID: 23735617