Histopathological diagnoses following toe amputations

Enlarged toes are often painful and cause lameness. They are often difficult or impossible to treat using antibiotics.

Amputation of the toe is then the only promising treatment option. It is a common surgery in enlarged toes of dogs and cats and patients usually recover well.

Amputations also offer the opportunity to both treat and diagnose the cause of the lesions, since the clinical presentation of neoplastic and non-neoplastic (Fig.1) lesions can be very similar.

Destruction of the bone in particular can be caused by malignant and benign tumors as well as by inflammation and other non-neoplastic lesions (e.g. hair follicle cysts). Bone destruction is often detected radiographically prior to toe amputation (Fig. 2). On the other hand, there are also cases in which no skeletal abnormalities are seen in which malignant bone destructive tumors are later diagnosed histologically.

Amputated toes should therefore always be examined by histopathology.

There is little data available on histopathological findings in amputated toes in dogs and cats.

The following analysis therefore looks at the histological results of 380 canine and 87 feline toe amputations submitted to LABOKLIN in order to demonstrate the frequency of possible diagnoses and their relationship to one another.

In individual cases, multiple lesions were found in single toes.

In dog toes, inflammatory processes with no indication of tumor growth were diagnosed in 118 cases (31.1%). This included various types of inflammation. Reactions to foreign material were frequently detected. These can cause extensive swelling of the toes. They can consist of introduced foreign materials like plant parts or hair that functions as endogenous foreign material following inflammatory processes or undirected growth. The type of inflammatory cells often indicates an additional bacterial infection. Some fungal infections as well as allergic reactions have also been observed.

If the inflammatory changes reach a chronic stage, increased granulation tissue is formed (Fig. 1).

Tumorous lesions were diagnosed in 249 (65.5%) cases (Tab. 2).

In cat toes (n=87) inflammatory lesions were diagnosed in 33 cases (37.9%). Tumorous processes were detected in 51 submissions (58.6%) (Tab. 2).

Similar frequency distributions have been described in other studies of dogs and cats (Wobeser et al., 2007a and b).

Squamous cell carcinoma

Squamous cell carcinomas of the toes (Fig. 2+3) begin in the stratum spinosum of the epidermis of the claw or the sole. At first, they can appear clinically similar to inflammation of the nail bed. This can lead to lameness, swelling of the toe and ulcerations. The nail frequently appears softened and splintered. The tumor has a local invasive growth and, in advanced stages, leads to bone destruction.

In the literature, metastasis rates of 5 to 29% have been described.

Amputation of the toe is the therapy of choice. The risk of recrudescence is considered low if carried out correctly (resection in healthy tissue).

Standard and giant schnauzers have a breed predilection.

Subungual keratoacanthoma

Subungual keratoacanthomas, like squamous cell carcinomas, originate from the stratum spinosum of the epidermis. They form defined nodular growths with a central callus. Subungual keratoacanthomas can transform into malignant squamous cell carcinomas. They can displace bone tissue due to their expansive growth and can also cause lytic changes.

Melanoma

Melanocytic tumors of the toes (Fig. 4) can arise from melanocytes of the epidermis of the claws or the skin between the toes. Independent of their histological differentiation, they are often malignant on the toes. Despite amputation, metastasis is common, especially to the lymph nodes and the lung.

Carcinoma of the toes of the cat

In cats, tumors on the toe are frequently metastases of other primary tumors. Bronchial carcinomas in particular have a tendency to metastasize to the toes.