Pathology in Practice.

In collaboration with the American College of Veterinary Pathologists.

Feline mesothelioma: case report and review of cytologic, immunocytochemical, histopathologic, and immunohistochemical findings.

Mesotheliomas are uncommon neoplasms that arise from mesothelial cells in either the abdominal or thoracic cavities and are rarely diagnosed in cats. A 10-y-old spayed female domestic shorthair cat was presented to the Louisiana State University oncology service for evaluation of a large amount of abdominal effusion. Abdominal ultrasound identified a large mesenteric mass with numerous ill-defined nodules. An abdominocentesis was performed with cytologic and immunocytochemical findings consistent with a neoplastic effusion, with large clusters of epithelioid cells that exhibited strong cytoplasmic expression of pancytokeratin, vimentin, and Wilms tumor 1 antigens. Further testing was declined, and meloxicam was prescribed until the cat died 23 d after initial presentation. Upon postmortem examination, the omentum was contracted into a firm mass adhered to multiple organs and accompanied by numerous small white nodules throughout the abdominal cavity. On histopathology and immunohistochemistry, neoplastic cells were found throughout the abdominal cavity; 60-95% exhibited moderate-to-strong cytoplasmic immunoreactivity for cytokeratin, vimentin, and Wilms tumor 1 protein. The final diagnosis was an epithelioid mesothelioma. Our case illustrates the utility of cytology, immunocytochemistry, and its relation to histology and immunohistochemistry. We also reviewed the reported cases of feline mesothelioma.

Rhabdochlamydia spp. in an Oregon raptor.

PCR-based approach was used to examine the rate of Chlamydia positivity in raptors from wild bird rehabilitation centers in Oregon. Three of 82 birds were identified as positive for Chlamydia with this PCR. Sequence analysis of 16S ribosomal DNA from 2 of these birds confirmed the presence of DNA from phylum Chlamydiae. One bird was positive for Chlamydia psittaci in both choanal and cloacal swabs. The second bird, a louse-infested red-tailed hawk, had evidence of choanal colonization by "Candidatus Rhabdochlamydia" spp. Our study describes evidence of this Chlamydia-like organism in the United States. This survey also suggests that the carriage rate of C. psittaci is low in raptors in Oregon wild bird rehabilitation centers, and that care must be taken in the design of PCR primers for phylum Chlamydiae such that colonization by insect endosymbionts is not mistaken for an infection by known chlamydial pathogens.