Inflammatory mammary carcinoma in dogs: 33 cases (1995-1999)

Objective-To determine epidemiologic, clinical, and pathologic characterist ics of inflammatory mammary carcinoma (IC) in dogs. Design-Retrospective study. Animals-33 dogs with IC and 153 dogs with malignant mammary tumors other th an IC. Procedures-Medical records were reviewed, and signalment, history, physical examination findings, and results of thoracic radiography and necropsy wer e obtained. Results-33 of 436 (7.6%) dogs examined at a veterinary teaching hospital because of dysplasia or tumors of the mammary glands and 33 of 18 6 (17.7%) dogs with at least 1 malignant tumor had IC. Thirty-two of the 33 dogs were sexually intact. Dogs with IC were significantly older than were dogs with other malignant mammary tumors, and in dogs with IC, the tumor w as initially noticed a mean of 52 days after the beginning of the last obse rved estrus, whereas in dogs with other mammary tumors, the tumor was initi ally noticed a mean of 137 days after the beginning of the last observed es trus. Dogs with IC were more likely to be anorectic and to have generalized weakness, weight loss, and thoracic metastases. Dogs with IC survived a me an of 25 days with palliative treatment. Histologically, involvement of der mal lymphatic vessels was identified in 14 of 19 (74%) dogs with IC. Two cl inical forms of IC (primary and secondary) were identified. Dogs with prima ry IC had a worse clinical condition. Conclusions and Clinical Relevance-Results suggest that IC is an uncommon b ut distinct entity in dogs. A histologic finding of dermal lymphatic involv ement should be considered a hallmark for the pathologic diagnosis of IC in dogs.