Feline toe biopsy reveals a bigger problem
Erin Edwards, DVM, MS, DACVP
An amputated toe from an 11-year-old, female spayed, domestic shorthaired cat was submitted to the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) in College Station for histopathology. This cat had multiple swollen nails on the front feet. Histologically, the distal phalangeal bone (P3) and nailbed were heavily infiltrated by neoplastic epithelial cells (Figure 1). In some areas, these epithelial cells were coated with apical cilia (Figure 2), indicating a respiratory origin. This tumor was diagnosed as a metastatic pulmonary carcinoma and is a classic example of feline lung-digit syndrome.
In cats with feline lung-digit syndrome, there is metastasis of a primary pulmonary carcinoma to one or more digits. Affected cats often show no signs of pulmonary disease and typically present for swollen and/or painful toes. Interestingly, there are no reports of dewclaws being affected. Less commonly, these tumors can metastasize to other locations such as skeletal muscle, but these sites often go un-noticed compared to the digital metastases. Although cilia may be difficult to find histologically, the presence of a carcinoma in the digit, especially with multiple toes affected, should prompt diagnostic imaging of the thoracic cavity.
For more information about this case, contact Veterinary Pathologist, Dr. Erin Edwards, at the College Station facility. To learn more about TVMDL’s test services, visit tvmdl.tamu.edu or call 1.888.646.5623.
Figure 1: Carcinoma cells, which stain more basophilic, infiltrate the digital bone, which stains more eosinophilic, causing extensive lysis. The nail is seen on the right side of this image and has pale eosinophilic staining.
Figure 2: Neoplastic epithelial cells with apical cilia (arrow).