Mediastinal lymphoma in dogs is homogeneous compared to thymic epithelial neoplasia and is more likely to envelop the cranial vena cava in CT images.

In order to identify CT signs that could be used to distinguish cranial mediastinal lymphoma and thymic epithelial neoplasia, a retrospective case-control study was done. Associations between CT signs and diagnosis were tested using binary logistic regression and results expressed as odds ratio and 95% confidence interval. Sixty-two dogs that had thoracic CT and confirmed diagnosis of lymphoma (n = 33) or thymic neoplasia (n = 29) were sampled. Thymic neoplasms included 24 thymomas and five thymic carcinomas. Dogs with thymic epithelial neoplasia were significantly older than dogs with lymphoma (median age 8.6 years versus 6.0 years, P = .007), but there were no significant differences in prevalence of clinical signs. Diagnosis of thymic epithelial neoplasia was associated with heterogeneous attenuation in pre- (odds ratio 23.3, 95% confidence interval, 4.5-121.1) and post-contrast (odds ratio 30.7, 95% confidence interval, 3.6-265.0) images. Conversely, envelopment of the cranial vena cava by the mass was less likely with thymic epithelial neoplasia than lymphoma (odds ratio 0.07, 95% confidence interval, 0.007-0.66). Greater standard deviation of Hounsfield unit values in post-contrast images was associated with thymic epithelial neoplasia (P = .005). Based on ROC analysis, SD > 17HU of the mass in post-contrast images had a sensitivity of 72% and specificity of 79% for thymic epithelial neoplasia. There were no significant differences in morphology, prevalence of calcification, mediastinal lymphadenopathy, cranial vena cava invasion, collateral vessels, or pleural fluid associated with these tumors. Thymic epithelial neoplasms tended to occur in older dogs and were heterogeneous in CT images, whereas mediastinal lymphoma was more homogeneous and more likely to envelop the cranial vena cava.

Radiographic Differentiation of Cranial Mediastinal Lymphomas from Thymic Epithelial Tumors in Dogs and Cats.

In both dogs and cats, the most common cranial mediastinal masses (CMMs) are lymphoma and thymic epithelial tumors (TETs). Pretreatment differentiation of these tumors using fine needle aspiration or biopsy is essential because lymphomas are treated medically, whereas TETs are treated surgically. The purpose of this retrospective study was to determine whether thoracic radiographic findings can be used to aid clinicians in preliminarily differentiating the two tumor types before cytology or histopathology results become available. Medical records, available cytologic or histologic samples, and thoracic radiographs were evaluated for 62 dogs and 28 cats. Seventeen radiographic criteria were assessed by two examiners, and regression modeling was performed to test for significant predictors of tumor type. In dogs, CMMs with at least two well-defined radiographic margins on a lateral view and CMMs causing a rightward shift of the cardiac silhouette on a ventrodorsal or dorsoventral view were significantly more likely to be TETs than lymphomas (P < .001 and P < .01, respectively). No significant predictive variables were identified in cats. Radiographic findings do not eliminate the need for invasive sampling, but in dogs, they may guide the clinician in providing preliminary information to owners regarding the staging and therapeutic measures that may eventually be recommended.

Spontaneous mediastinal myeloid sarcoma in a common marmoset (Callithrix jacchus) and review of the veterinary literature.

BACKGROUND: Myeloid sarcoma is a rare manifestation of myeloproliferative disorder defined as an extramedullary mass composed of myeloid precursor cells. A 9-month old, female, common marmoset (Callithrix jacchus) had increased respiratory effort. METHODS: A complete necropsy with histology and immunohistochemistry was performed. RESULTS: The thymus was replaced by a firm, gray-tan mass with a faint green tint, filling over 50% of the thoracic cavity. Sheets of granulocytes, lymphoid cells, nucleated erythrocytes, megakaryocytes, and hematopoietic precursors of indeterminate cell lineage replaced the thymus, perithymic connective tissue, mediastinal adipose tissues, epicardium, and much of the myocardium. The cells demonstrated diffuse strong cytoplasmic immunoreactivity for lysozyme, and strong, multifocal membranous immunoreactivity for CD117. CONCLUSION: We report the first case of a myeloid sarcoma in a common marmoset (C. jacchus), similar to reported human cases of mediastinal myeloid sarcoma, and present a review of myeloproliferative diseases from the veterinary literature.

Suspected bilateral phrenic nerve damage following a mediastinal mass removal in a 17-week-old pug.

The anesthetic management of a pediatric pug for removal of a mediastinal mass is described. During recovery from anesthesia, the dog's respiratory pattern was compatible with bilateral diaphragmatic paralysis. Incidence, complications, possible treatments of phrenic nerve injury, problems of long-term mechanical ventilation, and alternative case management are discussed.

Lésion bilatérale suspectée du nerf phrénique après l'ablation d'une masse médiastinale chez un Pug âgé de 17 semaines. Nous décrivons la gestion anesthésique d'un Pug pédiatrique présenté pour l'ablation d'une masse médiastinale. Durant le réveil après l'anesthésie, le profil respiratoire du chien était compatible avec la paralysie diaphragmatique bilatérale. L'incidence, les complications et les traitements possibles d'une blessure du nerf phrénique, les problèmes de la ventilation mécanique à long terme et les solutions pour la gestion du cas sont discutés.(Traduit par Isabelle Vallières).

MEDIASTINAL LYMPHOMA AND CHYLOTHORAX IN A STRIPED SKUNK (MEPHITIS MEPHITIS).

Tumors are infrequently reported in skunks, with only a few case reports published in the literature. Chylothorax associated with mediastinal lymphoma was diagnosed in a captive 7-yr-old male striped skunk ( Mephitis mephitis ). The animal presented with anorexia and apathy. Supportive care and prednisolone improved the animal's clinical status for 2 wk preceding its death. Histopathology supported the clinical findings, and the tumor was classified as a mediastinal non-Hodgkin lymphoma, stage 2b, which has not been documented in the literature.

Concurrent cranial mediastinal Blastomyces granuloma and carcinoma with cranial vena caval syndrome in a dog.

This report describes an unusual progression of blastomycosis in a dog with concurrent mediastinal carcinoma. The dog was evaluated for respiratory distress. Diagnostic results revealed chylothorax and a cranial vena caval thrombus. Histopathology of the cranial mediastinal mass diagnosed mediastinal carcinoma and fungal granuloma. Intercurrent disease may complicate the clinical presentation and clinical course of blastomycosis.

Granulome médiastinal àBlastomyceset carcinome concomitant avec le syndrome d'une veine cave crâniale chez un chien. Ce rapport décrit une progression inusitée d'une blastomycose chez un chien atteint d'un carcinome médiastinal concomitant. Le chien a été évalué pour une détresse respiratoire. Les résultats diagnostiques ont révélé le chylothorax et un thrombus de la veine cave crâniale. L'histopathologie de la masse médiastinale crâniale a révélé un diagnostic de carcinome médiastinal et de granulome fongique. La maladie intercurrente peut compliquer la présentation clinique et l'évolution clinique de la blastomycose.(Traduit par Isabelle Vallières).

Thoracoscopic removal of cranial mediastinal masses in dogs is associated with a low conversion rate, excellent survival to discharge, and good long-term outcome.

OBJECTIVE: To report the complications and outcomes associated with thoracoscopic cranial mediastinal mass resection in dogs. ANIMALS: 49 client-owned dogs that underwent thoracoscopic cranial mediastinal mass removal. METHODS: This was a retrospective cohort study (January 1, 2014, to July 31, 2023), and the medical records of 49 client-owned dogs that underwent thoracoscopic cranial mediastinal mass removal were reviewed. The signalment, history, clinicopathologic features, perioperative complications, and long-term outcome were recorded. RESULTS: Preoperative myasthenia gravis (MG) and megaesophagus (ME) were identified in 17 of 49 (35%) dogs and 11 of 49 (22%) dogs, respectively. The median maximal tumor diameter on CT images was 4.7 cm (range, 2.7 to 8.5 cm). Nonemergent conversion to an open procedure was necessary in 4 of 49 (8%) dogs, and dogs with conversion to an open procedure had a significantly larger median maximal CT tumor diameter than dogs without conversion (P = .03). The most common tumor type was thymoma (37/49 [76%]). The overall median survival time for dogs with thymoma was 1,102 days (95% CI, 482 to upper bound not reached). The median survival time for dogs with thymoma and concurrent presurgical MG was 182 days (95% CI, 14 to upper bound not reached). Presurgical diagnosis of MG (P = .44) or ME (P = .69) was not associated with survival time. CLINICAL RELEVANCE: Thoracoscopic removal of cranial mediastinal masses was associated with low conversion and complication rates. Long-term survival is possible, and thoracoscopic removal should be considered for select cases.

[Thymoma in a young adult cat]. / Thymom bei einer jung-adulten Katze.

Thymomas and mediastinal lymphomas are the most common mediastinal neoplasms in cats. While mediastinal lymphoma occurs primarily in younger cats (approximately 2 to 4 years of age), thymomas are diagnosed almost exclusively in older cats. However, the following case shows that this is not necessarily always the case.A 3-year- and 11-month-old neutered male European Shorthair was presented with a preliminary report of exercise intolerance and restricted respiration. Both symptoms occurred primarily at high ambient temperatures. Radiographically, a mediastinal mass filled a significant part of the thoracic cavity. A computed tomographic examination and ultrasound-guided TruCut biopsy were performed. Histologic examination suggested a thymoma. A sternal thoracotomy and resection of the circumferential proliferation was conducted. Subsequent histopathologic examination confirmed the suspected diagnosis of a mediastinal thymoma. The cat recovered well postoperatively, and a clinical and radiographic follow-up examination was unremarkable after 8 months.

Mediastinal teratoma in a free-ranging American black bear (Ursus americanus).

A 2.75-yr-old female American black bear (Ursus americanus) was found emaciated and unable to rise. It was euthanized due to the perceived poor prognosis. An approximately 18 x 8 x 10-cm, multiloculated, well-demarcated mass that extended from the bifurcation of the trachea, laterally displacing the lung lobes and caudally displacing the heart. The mass contained fibrous connective tissue, cartilage, bone, nervous tissue, smooth muscle, and a variety of epithelial structures. A mediastinal teratoma was diagnosed based on the microscopic features of the neoplasm.

Amyloid deposition in 2 feline thymomas.

Two cases of feline thymoma with amyloid deposition were encountered between 1982 and 2010. Neoplastic cells were separated by abundant, pale eosinophilic, homogeneous material that was congophilic and birefringent. Ultrastructurally, the neoplastic cells were connected by desmosomes, and the extracellular deposits were composed of nonbranching, hollow-cored fibrils, 8-10 nm in diameter. In the case with sufficient archived tissue for additional sections, the amyloid remained congophilic following potassium permanganate incubation, and the neoplastic cells were immunoreactive for pancytokeratin. The histologic, histochemical, ultrastructural, and immunohistochemical features of both neoplasms are consistent with epithelial-predominant thymoma with the unusual feature of intratumoral amyloid deposition. The affinity of the amyloid for Congo red following potassium permanganate incubation is consistent with non-AA amyloid. The ultrastructural findings were consistent with amyloid production by the neoplastic epithelial cells.

Cranial mediastinal liposarcoma in a horse.

A 23-year-old Anglo-Arabian mare was presented with tachypnea, dyspnea, and pitting edema of the ventral thoracic subcutis. On necropsy, a tan to red, friable, irregularly shaped mass (23 × 20 × 18 cm) occupied the cranial mediastinum. Histologically, the mass was classified as a liposarcoma and was composed of short interlacing bundles of spindle-shaped to irregularly rounded cells with discrete, variably sized, clear cytoplasmic vacuoles, which were stained with oil red O in frozen sections of formalin-fixed tissue.

Thymomas in rabbits: clinical evaluation, diagnosis, and treatment.

Thymomas are rarely recorded in rabbits, and the literature includes comparatively few cases. Medical records were reviewed to identify all pet rabbits in which a mediastinal mass was diagnosed between Feb 2007 and Jan 2010. Signalment, history, clinical signs, diagnostic work-up (including laboratory data, diagnostic imaging, and ultrasound-guided fine-needle aspiration of the mediastinal mass), treatment modalities, survival time, and histologic findings were evaluated. Cytologic and/or histopathologic examinations revealed thymomas in all rabbits with mediastinal masses (n=13). Rabbits with thymomas showed clinical signs of dyspnea (76.9%), exercise intolerance (53.9%), and bilateral exophthalmos (46.2%). In seven rabbits the thymoma was removed surgically. Two rabbits were treated conservatively, and four rabbits were euthanized because of their poor clinical condition. The two rabbits that underwent surgery were euthanized 6 mo and 34 mo later. Mediastinal masses in rabbits appear to be more common than previously believed and consist primarily of thymomas rather than thymic lymphomas. Cytology of samples collected by ultrasound-guided fine-needle aspiration is an accurate diagnostic tool for the identification of thymomas in rabbits. Due to a high rate of perioperative mortality, intensive perioperative care and the provision of a low-stress environment are recommended for a successful thoracotomy.

Mediastinal basaloid carcinoma arising from thymic cysts in two dogs.

Mediastinal masses in dogs were diagnosed as basaloid carcinoma associated with multiple thymic cysts (MTCs). The masses were composed of MTCs and proliferating intracystic neoplastic basaloid cells, which immunohistochemically diffusely expressed p63 and cytokeratin 19. A gradual transition from the basal cell layers lining the cysts walls to the neoplastic cells was seen, and it was indicated that the neoplastic cells had originated from the basal cell layers of the cysts. To the best of our knowledge, this is the first report of basaloid carcinoma occurring in the mediastinal cavity in dogs. Although these tumors were demonstrated to be rare origins, basaloid carcinoma should be included in the differential diagnoses for canine mediastinal tumors.

A rhabdomyoma within a multilocular thymic cyst in a p53-null mouse.

A 9-month-old p53-null female mouse was found dead in its cage. At necropsy, a large thymic mass encompassed the heart. Microscopically, the mass was composed of numerous varying-sized cysts lined with simple squamous epithelial cells to columnar ciliated cells. Also present within this mass was a large aggregate of loosely arranged fusiform-shaped cells. These cells also were found in smaller numbers in the connective tissue surrounding the cysts. The larger aggregate of fusiform cells was positive for desmin and S-100 and negative for smooth muscle actin. Electron microscopy revealed well-formed Z lines and I bands of skeletal muscle phenotype. A diagnosis of rhabdomyoma within a congenital multilocular thymic cyst was made. The thymus contains a small population of myoid cells, which should be taken in consideration when evaluating thymic tumors.

Clinicopathological characteristics and prognostic factors for canine multicentric non-indolent T-cell lymphoma: 107 cases.

Canine lymphoma, as the most common haematopoietic malignancy, encompasses a group of heterogeneous diseases and even within the T-cell immunophenotype, differences in clinical presentation and responses to treatment exist. The aim of this retrospective study was to determine outcomes and prognostic factors of 107 dogs with multicentric non-indolent T-cell lymphoma (TCL) receiving lomustine-based (70%) and non-lomustine-based (30%) treatment. The majority were Labradors, Boxers, mixed-breed dogs and Dogue de Bordeaux. Eighty-six percent were substage b, 77% had mediastinal involvement, 15% had suspected bone marrow involvement and 12% had other extra-nodal sites of disease. The overall response rate to induction therapy was 80%; dogs receiving procarbazine in the induction protocol (P = .042), dogs with neutrophil concentration below 8.7 × 10e9 /L (P = .006) and mitotic rate below 10 per 5 high power field (P = .013), had greater response rates. Median progression-free survival (PFS) for the first remission was 105 days; lack of expression of CD3 on flow cytometry (P < .0001) and pretreatment with steroid (P = .012) were significantly associated with shorter PFS. Median overall survival time (OST) was 136 days; co-expression of CD79a (P = .002), lack of CD3 expression on flow cytometry, presence of anaemia (P = .007), and monocytopenia (P = .002) were predictive of shorter OST. Multicentric non-indolent TCL in dogs is an aggressive cancer with new possible prognostic factors.

Lymphoepithelial thymoma characterized by proliferation of spindle cells in a Samoyed dog.

Lymphoepithelial thymoma was diagnosed in a 14-year-old Samoyed dog with clinical symptoms of myasthenia gravis at 6 months of age. At necropsy, dark red-colored mass with many nodular protuberances was found in the anterior mediastinal area. Histologically, the mass consisted of solid proliferation of neoplastic cells with spindle nuclei and cytoplasm and a few lymphocytes, which is separated by an abundant fibrous and adipose tissue. Immunohistochemically, spindle cells were positive for cytokeratin, and infiltrating lymphocytes were positive for CD3. On the basis of these findings, this tumor was diagnosed as lymphoepithelial thymoma, which is morphologically similar to type A thymoma in humans.

[Ultrasonographic and computed tomographic findings in a goat with mediastinal lymphocytic thymoma]. / Ultraschall- und CT-Befunde bei einer Ziege mit Thymom im Mediastinum.

This case report describes the clinical, sonographic, computed tomographic and pathological findings in a 9-year-old goat with mediastinal lymphocytic thymoma. The goat was referred to the Department of Farm Animals because of weight loss and dyspnoea. The lead clinical findings were increased heart rate, increased respiratory rate and heart sounds heard only on the right side. Ultrasonographic examination revealed a massive amount of fluid and an echogenic corrugated mass ventral to the lungs in the thoracic cavity on the left side. Computed tomography showed that the mass was very large and diffusely mineralised. A tentative diagnosis of mediastinal neoplasia was made, and the goat was euthanized. Postmortem examination revealed a cauliflower-like, pedunculated tumour, which occupied the entire left thoracic cavity and displaced the left lung. Based on histological evaluation, the tumour was diagnosed as a lymphocytic thymoma.

Mediastinal lymphoma with complete atrioventricular block in a horse.

A 15-year-old, neutered-male pony presented with a history of weight loss during 4 months. Clinical evaluation revealed severe bradycardia and complete atrioventricular block. At necropsy, a lobulated mass in the anterior mediastinum and moderate enlargement of the superficial cervical lymph nodes were observed. The vagus nerve and the brachiocephalic trunk were embedded in this anterior mediastinal tumor. Histologically, the mass was composed of sheets of neoplastic lymphoid cells expressing CD3, with a low mitotic rate. To the best of our knowledge, this is the first reported case of mediastinal lymphoma associated with complete atrioventricular block in horses.

Patient characteristics, prognostic factors and outcome of dogs with high-grade primary mediastinal lymphoma.

The goals of this retrospective study were to determine the patient characteristics of dogs with high-grade primary mediastinal lymphoma and to determine outcome and associated prognostic factors. A total of 42 dogs were identified, in which 36 received treatment and had follow-up information available. The most common clinical signs included lethargy, anorexia and polyuria/polydipsia. Hypercalcemia and pleural effusion were common findings at diagnosis. The phenotype was almost exclusively T-cell, most often in association with lymphoblastic cytomorphology as defined by the World Health Organization (WHO) lymphoma classification scheme. The overall progression-free survival (PFS) and overall survival (OS) were 133 and 183 days, respectively. Treatment with a CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) protocol was associated with an improved PFS (144 days) and OS (194 days) when compared with dogs that received other medical therapies (P = .005 and P = .002, respectively); the absence of pleural effusion at diagnosis was associated with an increased OS but not PFS. These results suggest that while the prognosis for dogs with mediastinal lymphoma is poor, survival may be improved with treatment using a CHOP-based protocol.