Subcutaneous chronic expanding hematomas in 6 dogs

Introduction: In human medicine, chronic expanding hematoma (CEH) is a slow-growing reactive lesion, often associated with trauma or surgery that can mimic soft tissue sarcoma (STS). Canine CEH has been reported in puppies with history of injection or trauma at the site of the lesion. Materials and methods: hematoxylin ad eosin stained sections of canine subcutaneous CEH were examined and histological findings were compared with 3 cases of injection-type panniculitis. Anamnesis and follow up were collected. Results: 6 cases were collected. Lesions measured between 3 and 20 cm and were located on ischial tuberosity (2/6), flank (2/6), neck and shoulder. Histology evidenced a central cavity surrounded by a three-layered capsule including an internal layer of immature granulation tissue, an intermediate layer with perpendicularly oriented vessels, and an external fibrous layer infiltrating the adjacent tissues. After surgery 3 cases recurred and 3 had delayed healing. Three cases of injection-type panniculitis evidenced similar features with a thinner capsule and less evident layering. Conclusions: Based on these findings CEH seems to represent an unusual evolution of necrotizing panniculitis, that can undergo post-surgical complication, and have to be differentiated from STS.

Introduction: Chronic expanding haematoma (CEH) is a slowgrowing reactive lesion that can mimic soft tissue sarcoma (STS) and that is associated with trauma or surgery in man. CEH has been reported in dogs following injection or trauma. Materials and Methods: Six cases of canine CEH were examined. Anamnesis and follow-up were collected. Tissues were processed routinely and stained. Microscopical findings in canine CEH were evaluated and compared with three cases of injection-type panniculitis (ITP). Results: CEHs were located on the ischial tuberosity (2/6), flank (2/ 6), neck and shoulder and ranged from 3 to 20 cm in diameter. Histology revealed a central cavity, containing fibrin and erythrocytes, surrounded by a multilayered capsule composed of an internal band of immature granulation tissue, an intermediate layer of perpendicularly oriented vessels and an external fibrous layer infiltrating adjacent tissues. After surgery, three cases recurred and three had delayed healing. Three cases of ITP lacked prominent layering, had a thinner capsule and mild inflammation. Conclusions: CEH may represent an uncommon evolution of necrotizing panniculitis that can undergo post-surgical complications and, because of the infiltrative growth, may need to be differentiated from STS.