Feline eosinophilic dermatoses: a retrospective immunohistochemical and ultrastructural study of extracellular matrix remodelling

Feline eosinophilic sclerosing fibroplasia – a characteristic inflammatory response in sites beyond the gastrointestinal tract: case report and proposed nomenclature

Case summary

An adult male neutered Russian Blue cat presented for a right-sided nasal mass with bilateral retropharyngeal and right mandibular lymphadenomegaly. Medial retropharyngeal lymph node excision with nasal mass biopsy revealed eosinophilic sclerosing lymphadenitis and eosinophilic and lymphoplasmacytic rhinitis, respectively. Bacterial culture of the lymph node grew Pseudomonas aeruginosa, and treatment with pradofloxacin was started. Despite initial improvement, clinical signs recurred after 9 months, and fine-needle aspirates of the right mandibular and left medial retropharyngeal lymph nodes showed eosinophilic and mastocytic infiltration. Bacterial culture of the left medial retropharyngeal lymph node grew P aeruginosa, and treatment with anti-inflammatory doses of prednisolone and, later, marbofloxacin was instituted.

Relevance and novel information

This report describes a case of feline eosinophilic sclerosing lymphadenitis diagnosed outside of the abdominal cavity and is the first case reported to be associated with P aeruginosa. Feline eosinophilic sclerosing lymphadenitis should be considered as a differential for lymphadenopathy occurring in areas other than the abdominal cavity. Feline eosinophilic sclerosing lymphadenitis may develop in cats due to a species-specific inflammatory response to chronic bacterial and fungal infections.

Feline Injection-Site Sarcoma

Feline injection-site sarcoma (FISS) is an aggressive tumor believed to arise from the proliferation of fibroblasts and myofibroblasts in areas of chronic inflammation, particularly at sites of injection. Local recurrence is frequent after surgical excision. Gelatinases (MMP-2 and MMP-9) and their inhibitor (TIMP-2) are endopeptidases pivotal in extracellular matrix remodeling and therefore in tumor invasiveness. The aim of this study was to investigate the immunohistochemical expression of MMP-2, MMP-9, and TIMP-2 in FISS to assess their usefulness as prognostic factors. Size, soft tissue sarcoma (STS) grading system, depth of infiltration, surgical margins, and Ki-67 index were evaluated as additional prognostic markers. Twenty-four cases of primary FISS were classified according to clinical follow-up as nonrecurrent (NR, n = 14; 58.3%) and recurrent (R, n = 10; 41.7%). MMP-2, MMP-9, and TIMP-2 were variably expressed in the FISS examined, confirming their role in tumor invasiveness, yet they did not show significant differences between the R and NR groups. These results could be due to different tumor stages or to the multiple activities of these enzymes, not limited to ECM remodeling. The immunohistochemical expression of these enzymes considered alone does not seem to be useful as a prognostic marker. STS grading system, depth of infiltration, surgical margins, and Ki-67 index did not relate to recurrence. Instead, the size of the tumor, measured after formalin fixation, with an optimal cutoff of 3.75 cm (accuracy = 86%; P < .05), and the mitotic count, with an optimal cutoff of 20 mitoses/10 HPF (accuracy = 80%; P < .05), could be evaluated as useful prognostic markers.