Mastocytosis in the skin in dogs: A multicentric case series.

Canine cutaneous mastocytosis (CM) is rare in contrast to canine mast cell tumours. In humans, CM commonly affects children and is usually indolent with possible spontaneous resolution. Systemic mastocytosis (SM) with bone marrow involvement typically affects adults, can have a poor outcome, and often includes skin lesions. 'Mastocytosis in the skin' (MIS) is the preferred term of skin lesions, if bone marrow evaluations are not available, which is often the cases in dogs. In human SM and CM, KIT mutations are often detected. The veterinary literature suggests clinical resemblances between human and canine MIS, but data is limited, and KIT mutations are rarely assessed. This retrospective study describes clinicopathological findings, treatment and outcome of 11 dogs with suspected MIS. Dogs with multiple mast cell tumours were excluded. Histopathology reports (n = 5) or slides (n = 6) were reviewed. KIT mutation analysis including exons 8, 9, 11, 14 and 17 were analysed in eight dogs. Median age at diagnosis was 4 years (range, 1-12). Typical clinical signs included multifocal to generalised nodules and papules. Histologically, skin lesions were characterised by dermal infiltration of well-differentiated mast cells. KIT mutations were detected in 3/8 dogs (exon 9: n = 2; exon 11: n = 1). One dog had mastocytaemia suggesting possible SM. Glucocorticoids were mostly successful with lesion improvement in all treated dogs (n = 8). This cohort highlights resemblances between human and canine MIS. Further studies are required to confirm these findings and establish diagnostic criteria for CM and MIS associated with SM in dogs.

Large granular lymphocyte lymphoma in 65 dogs (2005-2023).

Large granular lymphocyte lymphoma (LGLL) is a rare form of lymphoma in dogs. Limited information exists regarding presentation, treatment response, and outcome. The aim of this single-institute, retrospective study was to characterise clinical presentation, biologic behaviour, outcomes, and prognostic factors for dogs with LGLL. Cytologic review was also performed. Sixty-five dogs were included. The most common breed was the Labrador retriever (29.2%), and the most common presenting signs were lethargy (60.0%) and hyporexia (55.4%). The most common primary anatomic forms were hepatosplenic (32.8%) and gastrointestinal (20.7%). Twenty dogs (30.8%) had peripheral blood or bone marrow involvement. Thirty-two dogs were treated with maximum tolerated dose chemotherapy (MTDC) with a response documented in 74.1% of dogs. Dogs ≥7 years, and those with neutropenia or thrombocytopenia at diagnosis had the reduced likelihood of response to treatment. For dogs treated with MTDC median progression-free interval (PFI) was 17 days (range, 0-481), the median overall survival time (OST) 28 days (range, 3-421), and the 6-month and 1-year survival rates were 9.4% and 3.1%, respectively. On multivariable analysis, monocytosis and peripheral blood involvement were significantly associated with shorter PFI and OST. Long-term survival (≥100 days) was significantly associated with intermediate lymphocyte size on cytology. Dogs with LGLL have moderate response rates to chemotherapy but poor overall survival. Additional studies are needed to further evaluate prognostic factors and guide optimum treatment recommendations.

Prevalence of malignancy and factors affecting outcome of cats undergoing splenectomy.

OBJECTIVE: To determine the prevalence of splenic malignancy in cats undergoing splenectomy and to investigate possible factors associated with post-operative outcome. ANIMALS: 62 client-owned cats that underwent splenectomy. METHODS: Medical records of 4 UK-based referral hospitals were searched and data reviewed retrospectively over 17 years. Factors associated with outcomes post-splenectomy were analyzed. RESULTS: 50 out of 62 cats (81%) were diagnosed with splenic neoplasia. Mast cell tumor ([MCT], 42%), hemangiosarcoma ([HSA], 40%), lymphoma and histiocytic sarcoma (6% each) were the most common tumor types. Fifteen cats (24%) presented with spontaneous hemoabdomen and were all diagnosed with splenic neoplasia. The diagnostic accuracy of cytology to detect splenic malignant lesions was 73% (100% for MCTs and 54% for mesenchymal tumors). Median survival time for cats with nonneoplastic splenic lesions was 715 days (IQR, 18 to 1,368) and 136 days for cats with splenic neoplasia (IQR, 35 to 348); median survival time was longer for cats with splenic MCT when compared to cats with HSA (348 vs 94 days; P < .001). Presence of metastatic disease and anemia (PCV < 24%) at diagnosis were associated with a poorer survival when considering all cats. Presence of anemia, a splenic mass on imaging or spontaneous hemoabdomen were associated with a diagnosis of HSA (P < .001). CLINICAL RELEVANCE: Benign splenic lesions were uncommon in this cohort of cats. Spontaneous hemoabdomen should prompt the clinician to suspect neoplasia in cats with splenic disease. Anemia and evidence of metastasis at diagnosis were poor prognostic factors regardless of the final diagnosis.

Clinical presentation, treatment and outcome of canine malignant mesothelioma: A retrospective study of 34 cases.

Canine malignant mesothelioma (CMM) is a rare and aggressive tumour associated with a poor prognosis. Limited information is available regarding effective treatment options and prognostic factors. The purpose of this retrospective case series was to describe the clinical presentation, treatment and survival in a cohort of dogs with this disease and to investigate possible prognostic factors. Thirty-four dogs were included. Tachypnoea and dyspnoea due to pleural effusion were the most common presenting clinical signs. Twenty-two dogs had a subcutaneous access port placed and 25 dogs were treated with intracavitary and/or intravenous chemotherapy. The main protocols used were single-agent 5-FU (n = 14) and carboplatin single-agent or alternated with mitoxantrone (n = 10). The overall response rate (defined as more than 25% reduction in effusion volume) to chemotherapy treatment was 37% after 3-weeks and 24% after 15-weeks. The median survival time (MST) for all dogs was 195 days (95% CI 53-324). MST was 234 days for dogs receiving chemotherapy and 29 days for dogs not receiving chemotherapy. The 1-year survival rate was 22% for all dogs. Treatment with chemotherapy was the only significant prognostic factor associated with survival (p = .001). Further studies are needed to determine the optimal treatment approach for malignant mesothelioma in dogs. Nevertheless, effusion recurrence should be expected and the prognosis for these patients in the long-term is poor.

Immunohistochemical expression and prognostic significance of MAGE-A in canine oral malignant melanoma.

Canine oral malignant melanoma (COMM) is considered a chemo-resistant cancer with a poor long-term prognosis. The melanoma-associated antigen A (MAGE-A) genes, which belong to the cancer-testis antigen family, are expressed in several different canine cancers but not in normal somatic tissue. This study evaluates the expression of MAGE-A proteins and their prognostic role in COMM. The study was conducted in 2 parts. During the first part, biopsies from oral malignant melanomas from 43 dogs were examined and immunohistochemically assessed for expression of MAGE-A proteins. For the second part, the association between MAGE-A expression and outcome was assessed using follow-up data which was available for 20 dogs whose primary tumour had been controlled with surgery +/- radiation therapy. MAGE-A proteins were expressed in 88.4% (38/43) of oral malignant melanomas and had a predominantly cytoplasmic expression pattern. Immunopositivity was observed in more than 50% of the cells in 21 dogs (48.8%). Immunostaining intensity was classified as weak, moderate and intense in 16 (37%), 16 (37%) and 6 (14%) cases, respectively. No staining for MAGE-A was seen in 5 dogs (11%). Dogs whose COMM had weak MAGE-A staining intensity had a median survival time (MST) of 320 days while this was 129 days for dogs with moderate and intense immunostaining (p = 0.161). Dogs whose COMM had >50% of positive staining neoplastic cells had an MST of 141 days and dogs with a staining <50% had an MST of 320 days (p = 0.164). MAGE-A expression did not influence survival in our cohort.

Gastric Intravascular Lymphoma in a Dog: Case Report and Literature Review.

Intravascular lymphoma (IVL) is a rare, high-grade, extranodal lymphoma characterized by selective proliferation of neoplastic lymphocytes within the lumen of small vessels. A 10 yr old female intact mixed-breed dog was presented with a 7 mo history of vomiting and anorexia. Physical examination revealed abdominal discomfort. Ultrasonography and endoscopy identified a submucosal gastric mass. Excision was performed by partial gastrectomy and histopathology and immunohistochemistry confirmed a T-cell IVL. The owner declined chemotherapy, and the dog was instead treated palliatively with prednisolone. Two months after surgery, vomiting recurred and abdominal ultrasonography revealed a large gastric ulcer with focal peritonitis. The dog was euthanized 4 mo after initial presentation and postmortem examination confirmed IVL recurrence in the stomach and an isolated nodule of neoplastic cells in the omentum. No involvement of other organs was found following histopathological examination. This is the first description of primary gastric intravascular lymphoma causing chronic vomiting in a dog.

Non-islet-cell tumour hypoglycaemia in a cat with hepatocellular carcinoma.

CASE SUMMARY: An 11-year-old male neutered domestic shorthair cat presented with behavioural changes. Physical examination revealed bradycardia and a cranial abdominal mass. The cat was persistently hypoglycaemic (1.2 mmol/l; reference interval [RI] 3.5-5.5 mmol/l) with decreased fructosamine concentration suggesting chronic hypoglycaemia, and decreased insulin concentration excluding insulinoma. Alanine aminotransferase activity was markedly increased (1219.31 U/l; RI 15-60 U/l). On staging CT a large, multilobulated hepatic mass was identified, with no evidence of metastatic disease. After surgical removal serum glucose concentration and heart rate quickly returned to within the RIs. Histopathology was consistent with a solid-to-trabecular, well-differentiated, hepatocellular carcinoma. There was no recurrence of signs or mass during 8 months of follow-up, and the cat was still alive 20 months after surgery. RELEVANCE AND NOVEL INFORMATION: Non-islet-cell tumour hypoglycaemia (NICTH) is a rare but life-threatening paraneoplastic syndrome. In humans, hepatocellular carcinoma is the most common epithelial tumour causing NICTH, but these are uncommon in cats, and associated paraneoplastic hypoglycaemia has not been reported. Possible mechanisms include aberrant secretion of big insulin growth factor 2; however, this could not be confirmed. NICTH should be considered in the differential diagnosis of cats with persistent hypoglycaemia.