SKELETAL METASTASIS AS THE INITIAL CLINICAL MANIFESTATION OF METASTATIC CARCINOMA IN 19 DOGS

Although the skeleton represents a potentially important target for th e metastatic spread of carcinoma, the clinicopathologic features of sk eletal metastases in dogs have not been documented extensively. In par ticular, no reports have focused on dogs in which skeletal metastasis was the initial clinical manifestation of their malignancy. Medical re cords were reviewed for dogs with skeletal carcinoma and cases were su bdivided into 2 groups based upon the temporal relationship between th e diagnosis of carcinoma and recognition of skeletal metastases. In 19 of 24 (79%) dogs, skeletal metastasis was the initial clinical manife station of malignancy, and these dogs were studied in detail. Most aff ected dogs were elderly and weighed less than 25 kg. Thirty-six skelet al lesions were identified in 19 dogs. Skeletal metastases occurred mo st frequently in the axial skeleton and proximal long bones. Only 4 of 36 (11%) skeletal carcinomas occurred distal to the elbow or stifle. Mammary gland, prostate, and urinary bladder were the most common prim ary sites. In 11 of 19 (58%) dogs, the primary tumor could not be dete rmined, and in 6 of these dogs, the primary tumor could not be identif ied despite complete postmortem evaluation. Physical examination and a bdominal ultrasonography were most valuable in detecting the primary t umor. Although biopsy or fine-needle aspirate of skeletal lesions was essential in the diagnosis of skeletal carcinoma, these procedures did not yield definitive information on the primary tumor site. This repo rt documents that the majority of skeletal metastases are diagnosed in dogs without a previous diagnosis of carcinoma. Detection of the prim ary tumor in:these cases may be challenging, and skeletal metastases a re frequently attributable to carcinoma of unknown origin.