Clinical, histopathological and immunohistochemical features ofa thymoma in a domestic rabbit (Oryctolagus cuniculus): casereport

Thymoma is a neoplasm originating from epithelial cells of the thymus. It represents the most common tumor in the mediastinal region of rabbits, followed by lymphoma. This study aims to report a case of post mortem diagnosis of thymoma in a rabbit (Oryctolagus cuniculus), with the purpose to contribute to the understanding of this disease and its diagnosis in this specie. A six-year-old male mixed breed pet rabbit (O. cuniculus), weighing 2.3 kg, was referred to necropsy exam. The previous clinical history included prostration, lethargy, weight loss, dysorexia and respiratory distress, evidenced mainly on the expiratory phase. Radiographs revealed pleural effusion and the presence of a mass involving the cranial and middle mediastinum, confirmed by ultrasound. In the cytological examination, it was diagnosed as a low-gradelymphoma and chemotherapy was performed with COP (cyclophosphamide, vincristine Oncovin®, prednisolone). However, after 145 days, euthanasia was performed. At necropsy, a well delimited mass was observed in the mediastinal region, adhered to the pleura, with firm consistency and pale coloration. Histopathological analysis of the mass showed the proliferation of epithelial neoplastics cells, arranged in trabeculas and with infiltration of small lymphocytes. The immunohistochemical findings included cytoplasmic immunolabeling for cytokeratin AE1/AE3 in 90% of epithelial neoplastics cells, while CD3 was evidenced in a small number of lymphocytes (T-lymphocytes) and CD79a in Blymphocytes localized on the neoplasia periphery. The growth fraction was estimated at 30% by Ki-67. According to the histopathological criteria for thymoma classification proposed by the World Health Organization, 2015, it was made the diagnosis of lymphocyte-rich predominantly cortical thymoma (B1 type).(AU)

Clinical, histopathological and immunohistochemical features ofa thymoma in a domestic rabbit (Oryctolagus cuniculus): casereport

Thymoma is a neoplasm originating from epithelial cells of the thymus. It represents the most common tumor in the mediastinal region of rabbits, followed by lymphoma. This study aims to report a case of post mortem diagnosis of thymoma in a rabbit (Oryctolagus cuniculus), with the purpose to contribute to the understanding of this disease and its diagnosis in this specie. A six-year-old male mixed breed pet rabbit (O. cuniculus), weighing 2.3 kg, was referred to necropsy exam. The previous clinical history included prostration, lethargy, weight loss, dysorexia and respiratory distress, evidenced mainly on the expiratory phase. Radiographs revealed pleural effusion and the presence of a mass involving the cranial and middle mediastinum, confirmed by ultrasound. In the cytological examination, it was diagnosed as a low-gradelymphoma and chemotherapy was performed with COP (cyclophosphamide, vincristine – Oncovin®, prednisolone). However, after 145 days, euthanasia was performed. At necropsy, a well delimited mass was observed in the mediastinal region, adhered to the pleura, with firm consistency and pale coloration. Histopathological analysis of the mass showed the proliferation of epithelial neoplastics cells, arranged in trabeculas and with infiltration of small lymphocytes. The immunohistochemical findings included cytoplasmic immunolabeling for cytokeratin AE1/AE3 in 90% of epithelial neoplastics cells, while CD3 was evidenced in a small number of lymphocytes (T-lymphocytes) and CD79a in Blymphocytes localized on the neoplasia periphery. The growth fraction was estimated at 30% by Ki-67. According to the histopathological criteria for thymoma classification proposed by the World Health Organization, 2015, it was made the diagnosis of lymphocyte-rich predominantly cortical thymoma (B1 type).

Timoma canino associado à miastenia gravis / Canine thymoma associated to myasthenia gravis

Background: Thymomas are epithelial neoplasms of the thymus, although lymphocyte infiltration is common. Histological features are not sufficient to define its biological behaviour, which is dependent of clinical criteria of invasiveness and resectability. Myasthenia gravis may happen as a paraneoplastic syndrome in up to 47% of canine thymomas. This article aims at reporting a case of thymoma associated with myasthenia gravis in a dog, emphasizing the morphological, phenotypical and therapeutical aspects.Case: A 7-year-old, male Labrador, was presented with a history of acute dyspnea and exercise intolerance. The physical examination revealed a “red-brick” mucousa, tachycardia and cardiac and pulmonar hypofonese. Chest radiographs revealed an area of increased radiopacity in the cranial mediastinum without a plane of separation to the heart. The eccodopplercardiogram exam identified a poorly delimited mass adjacent to the base of the heart, measuring 9.5x6.8cm. Computed tomography demonstrated it as an expansive neoformation (9.5x6.5x7.8cm). Mass was removed through intercostal thoracotomy and the removed tissue was submitted to histopathology with a diagnosis compatible with type AB thymoma (mixed). Immunohistochemistry was positive for AE1/AE3 citokeratin in 90% of epithelial cells, confirming tumour origin. Tumour infiltrating lymphocytes were positive for CD79a (70%) and CD3 (20%). The proliferation index (Ki-67 imunolabeling) was 60%. About 45 days after surgery the patient was presented with generalized muscle weakness and regurgitation, with confirmed megaesophagus on chest X-ray. Treatment with pyridostigmine was initiated because of suspected myasthenia gravis, and complete remission of the neurological signs occurred within a month. A chemotherapeutic protocol with carboplatin was then instituted. After four sessions, a new thoracic radiograph revealed tumour recurrence in the cranial mediastinum.[...]

Timoma canino associado à miastenia gravis / Canine thymoma associated to myasthenia gravis

Background: Thymomas are epithelial neoplasms of the thymus, although lymphocyte infiltration is common. Histological features are not sufficient to define its biological behaviour, which is dependent of clinical criteria of invasiveness and resectability. Myasthenia gravis may happen as a paraneoplastic syndrome in up to 47% of canine thymomas. This article aims at reporting a case of thymoma associated with myasthenia gravis in a dog, emphasizing the morphological, phenotypical and therapeutical aspects.Case: A 7-year-old, male Labrador, was presented with a history of acute dyspnea and exercise intolerance. The physical examination revealed a “red-brick” mucousa, tachycardia and cardiac and pulmonar hypofonese. Chest radiographs revealed an area of increased radiopacity in the cranial mediastinum without a plane of separation to the heart. The eccodopplercardiogram exam identified a poorly delimited mass adjacent to the base of the heart, measuring 9.5x6.8cm. Computed tomography demonstrated it as an expansive neoformation (9.5x6.5x7.8cm). Mass was removed through intercostal thoracotomy and the removed tissue was submitted to histopathology with a diagnosis compatible with type AB thymoma (mixed). Immunohistochemistry was positive for AE1/AE3 citokeratin in 90% of epithelial cells, confirming tumour origin. Tumour infiltrating lymphocytes were positive for CD79a (70%) and CD3 (20%). The proliferation index (Ki-67 imunolabeling) was 60%. About 45 days after surgery the patient was presented with generalized muscle weakness and regurgitation, with confirmed megaesophagus on chest X-ray. Treatment with pyridostigmine was initiated because of suspected myasthenia gravis, and complete remission of the neurological signs occurred within a month. A chemotherapeutic protocol with carboplatin was then instituted. After four sessions, a new thoracic radiograph revealed tumour recurrence in the cranial mediastinum.[...](AU)

Mixed Thymoma in a Goat

This article describes the gross, histopathological, and immunohistochemical findings of a mixed thymoma in a 2-year-old, mixed-breed, female goat. A large space-occupying neoplastic growth was observed within the cranial thoracic cavity, which by histology was well-encapsulated and formed by the proliferation of spindle-shaped epithelial cells arranged in solid sheets or rosette-like formations with varying accumulations of lymphocytes. Immunohistochemistry demonstrated that the neoplastic epithelial cells expressed cytokeratin, with negative immunoreactivity to vimentin, thyroglobulin, Chromogranin A, neuron-specific enolase, and glial fibrillary acidic protein. The lymphocytic population expressed CD3 and CD2. These findings favor a diagnosis of mixed thymoma.(AU)

Mixed thymoma in a German Shepherd dog

A thoracic neoplastic mass in a 6 years-old German Shepherd dog was examined. The dog had apathy, regurgitation, and ascites. A large mass occupying the cranioventral, medial and caudal mediastinum was found by X ray and ultrasonography. Grossly, a 27 x 23 x 12 cm encapsulated, multilobulated, and cystic mass was found. Firms adhesions were present between the neoplasm and the right and left cranial lung lobes. Histopathologically, the neoplastic cell population consisted of solids sheets of epithelial cells and aggregates or individual lymphocytes. By immunohistochemistry, proliferating epithelial cells were positive for keratin and lymphocytes were intensely positive for CD3, identifying them as T cells. Based on gross, histologic, and immunohistochemical findings, the neoplasm was diagnosed as a mixed thymoma.

Mixed thymoma in a goat

This article describes the gross, histopathological, and immunohistochemical findings of a mixed thymoma in a 2-year-old, mixed-breed, female goat. A large space-occupying neoplastic growth was observed within the cranial thoracic cavity, which by histology was well-encapsulated and formed by the proliferation of spindle-shaped epithelial cells arranged in solid sheets or rosette-like formations with varying accumulations of lymphocytes. Immunohistochemistry demonstrated that the neoplastic epithelial cells expressed cytokeratin, with negative immunoreactivity to vimentin, thyroglobulin, Chromogranin A, neuron-specific enolase, and glial fibrillary acidic protein. The lymphocytic population expressed CD3 and CD2. These findings favor a diagnosis of mixed thymoma.

Mixed thymoma in a German Shepherd dog

A thoracic neoplastic mass in a 6 years-old German Shepherd dog was examined. The dog had apathy, regurgitation, and ascites. A large mass occupying the cranioventral, medial and caudal mediastinum was found by X ray and ultrasonography. Grossly, a 27 x 23 x 12 cm encapsulated, multilobulated, and cystic mass was found. Firms adhesions were present between the neoplasm and the right and left cranial lung lobes. Histopathologically, the neoplastic cell population consisted of solids sheets of epithelial cells and aggregates or individual lymphocytes. By immunohistochemistry, proliferating epithelial cells were positive for keratin and lymphocytes were intensely positive for CD3, identifying them as T cells. Based on gross, histologic, and immunohistochemical findings, the neoplasm was diagnosed as a mixed thymoma.

Thymoma in the dog. Case report / Timoma em cão. Relato de caso

A four years old Dachshund female dog was guided to the Veterinary Hospital of FMVZ-UNESP-Botucatu-SP with history of prostration, progressive weigh loss, anorexia, fatigue and drought coughs. Apathy, serous bilateral nasal discharge, intense dyspneia and lung edema were observed in the clinical exam. Thoracic X-ray showed pleural effusion and dorsal deviation of trachea and the presence of a mediastinal mass. The ultrasonography, after thoracic drainage and fine needle aspiration cytology, confirmed the presence of mediastinal mass classified as malignant neoplasm of epithelial origin. The animal died soon after the exams due to its bad clinical conditions. At necropsy mediastinal mass was located in the antero-ventral area of the thorax. It was encapsulated, with soft consistency and gray coloration with hemorragic and necrotic areas in the cut surface. The histopathology demonstrated neoplastic epithelial cells, lymphoid cells (thymocytes) with normal morphology, blood vessels of small and medium caliber, cystic formations with eosinophilic contents and Hassall corpuscles. The immunohistochemistry reaction was positive for cytokeratin AE1/AE3 and UCHL, confirming the thymoma diagnosis.

Uma cadela, Dachshund, quatro anos, foi encaminhada ao H.V. da FMVZ-UNESP-Botucatu-SP com histórico de prostração, emagrecimento progressivo, anorexia, cansaço e tosse seca. Ao exame clínico observou-se apatia, secreção nasal serosa bilateral e dispnéia intensa. Radiografia torácica demonstrou efusão pleural, edema pulmonar acentuado, desvio dorsal da traquéia e possível massa mediastinal. A ultra-sonografia, após drenagem torácica, confirmou a presença de massa mediastinal, sendo classificada como neoplasia maligna de origem epitelial pela citologia aspirativa por agulha fina. O animal veio a óbito logo após o diagnóstico de neoplasia. À necropsia constatou-se massa mediastinal encapsulada, consistência macia e superfície de corte com coloração branco-acinzentada e áreas necrótico-hemorrágicas, localizada na região ântero-ventral do tórax. O exame histopatológico demonstrou células epiteliais neoplásicas, células linfóides (timócitos) com morfologia normal, vasos sangüíneos de pequeno e médio calibre, formações císticas com conteúdo eosinofílico e corpúsculos de Hassall. A imunohistoquímica apresentou positividade para citoqueratina AE1/AE3 e UCHL, confirmando o diagnóstico de timoma.

Miastenia gravis análise de 90 casos tratados com timectomia myasthenia gravis

A Miastenia Gravis é uma doença auto-imune caracterizada por auto-anticorpos contra receptores nicotínicos de acetilcolina da placa neural. O tratamento clínico básico para as formas generalizadas é feito com drogas anticolenesterásicas, mas em algumas fases podem ser necessários outras modalidades de tratamento, tais como a corticoterapia e a plasmaferese. O tratamento cirúrgico, a timectomia, é uma forma de abordar a causa base da doença e tem resultados bastante encorajadores, visto que é atribuída ao timo a produção dos auto-anticorpos. Apresentamos neste trabalho o quadro clínico, os resultados cirúrgicos e as alteração anátomo-patológicas dos 90 casos estudados.

Miastenia gravis análise de 90 casos tratados com timectomia myasthenia gravis

A Miastenia Gravis é uma doença auto-imune caracterizada por auto-anticorpos contra receptores nicotínicos de acetilcolina da placa neural. O tratamento clínico básico para as formas generalizadas é feito com drogas anticolenesterásicas, mas em algumas fases podem ser necessários outras modalidades de tratamento, tais como a corticoterapia e a plasmaferese. O tratamento cirúrgico, a timectomia, é uma forma de abordar a causa base da doença e tem resultados bastante encorajadores, visto que é atribuída ao timo a produção dos auto-anticorpos. Apresentamos neste trabalho o quadro clínico, os resultados cirúrgicos e as alteração anátomo-patológicas dos 90 casos estudados.