Diagnosis and management of a case of retroperitoneal eosinophilic sclerosing fibroplasia in a cat

Thieme, Maureen E; Olsen, Anastasia M; Woolcock, Andrew D; Miller, Margaret A; Simons, Micha C

FGESF is an inflammatory condition of unknown etiology in domestic cats. 1 It has a worldwide distribution, and has been diagnosed in the USA, Europe, Japan and New Zealand. 1-7 FGESF affects cats ranging in age from 14 weeks to >16 years, with the median age being 7-8 years. 1, 3 Males and Ragdoll cats may be over-represented. 3 Clinical signs commonly include chronic vomiting and/or diarrhea, weight loss, lethargy and anorexia. 1, 3, 7 As in the described case, a palpable abdominal mass is found in the majority (~85%) of cats, in addition to abdominal pain. 3 Other findings may include pyrexia and peripheral eosinophilia (~58%). 1, 3 Diagnostic imaging such as abdominal radiography or ultrasonography may be performed to identify an abdominal mass, but they cannot be used to distinguish FGESF from intestinal neoplasia. 7 Macroscopically, FGESF typically manifests as a nodular, ulcerated, intramural gastrointestinal mass most commonly affecting the pylorus or ileocecocolic junction, although masses in the duodenum, jejunum and colon have been described. 1-7 Involvement of regional abdominal lymph nodes and eosinophilic inflammation within adjacent tissues, such as the pancreas or liver, has also been described. [1] [2] [3] Extension into the mesenteric and cranial mediastinal lymph nodes has been reported in one cat. 5 Gross lesions may be confused with lymphoma, adenocarcinoma, granulomatous disease or soft tissue sarcoma. 1, 3, 7 Microscopically, FGESF is characterized by trabeculae of dense sclerotic collagen, large, reactive fibroblasts and mixed inflammation of many eosinophils with fewer well-granulated mast cells, neutrophils, plasma cells, lymphocytes and/or macrophages. [1] [2] [3] [4] [5] [6] [7] [8] Histologically, these inflammatory lesions have been There is a single ovoid contrast-enhancing, soft tissue-attenuating mass (white arrows) present within the pelvic canal causing ventral displacement and narrowing of the rectum at the level of the sacrum mistaken for sclerosing mast cell tumors and intestinal osteosarcomas in some cats. 9 Examination of biopsies sampled from the described cat's caudal abdominal mass was consistent with previously reported histologic findings. Biopsy of a regional lymph node revealed eosinophilic lymphadenitis, indicating probable extension of this lesion into local lymph nodes, as reported. 5 Although a specific cause has not been identified, proposed pathogeneses include inherited eosinophil dysregulation, food hypersensitivity, penetrating wound from a migrating foreign body, herpesvirus infection or bacterial infection. [1] [2] [3] [4] [5] [6] [7] [8] Certain cats may be genetically predisposed to significant eosinophilic inflammation in response to antigenic stimulation from bacteria, fungi or parasites. 8 Bacteria are isolated from lesions in about 56% of cases; however, it is unclear whether the bacteria have a primary or secondary role. 1 Most commonly, Gram-negative rods are isolated; however, Grampositive rods and Gram-positive cocci, as isolated in the described case, have been reported. One case report previously identified phycomycetes in a domestic cat with FGESF, and similar lesions have been found in the pylorus of pumas infected with intestinal nematodes (Cyclospirura species), which may indicate this sclerotic reaction is a felid-specific inflammatory response to infection of varying causes. 8 A recent study aimed to explore the possible involvement of feline herpesvirus-1 (FHV-