Fibroma cutâneo atípico em uma vaca / Atypical cutaneous fibroma in a cow

Background: Cutaneous fibroma is a benign neoplasm affecting the fibroblasts and collagen matrix that develops in the dermis or subcutaneous tissue. This neoplasm is uncommon in cattle, and few reports have described the treatment and resolution of this neoplasm. Despite its benign character, a veterinarian should consider cutaneous fibroma in the differential diagnosis of skin tumors. This report aims to describe a rare case of large fibroma in the scapular region in a cow, with emphasis on the clinical-surgical and anatomopathological aspects of the condition. Case: A 3-year-old Girolando 3/4 cow was attended to at a rural property in Lagamar-MG, Brazil. According to the owner, the animal presented with a small mass in the right scapular region that grew progressively over 1 year and 6 months. Clinical examination revealed an exuberant and painless increase in volume on palpation in the proximal region of the right thoracic limb, which, in its vertical axis, extended from the proximal end of the scapula to near the olecranon tuberosity, and, in its horizontal axis, extended from the 6th intercostal space to the scapulohumeral joint, reaching the dimensions 66 cm and 62 cm, respectively. It presented with multiple nodules that were firm in consistency with extensive areas of ulceration. Neoplasia was suspected, and surgical excision was decided upon. The cow was sedated and restrained in the left lateral decubitus position. Trichotomy and antisepsis of the operative field were performed followed by an infiltrative anesthetic block around the tumor. The tumor was excised maintaining a safety margin of 1 cm. Dermorrhaphy was not possible, and healing by secondary intention was awaited. In the postoperative period, antibiotic therapy with benzathine penicillin, analgesia with meloxicamand dipyrone and daily dressing of the wound were performed. There were no postoperative complications and complete healing occurred approximately 100 days after surgery. One year after the surgical procedure, the owner reported that the cow did not present with recurrence of the neoplasm. The resected tumor weighed 11.2 kg, and, when cut, presented with solid conformation and whitish coloration. Tumor fragments were harvested, fixed in 10% formalin, and sent for histopathological examination, which revealed neoproliferation of remarkable cellular density composed of dense, well vascularized fibrocollagenous connective tissue arranged in multidirectional bundles and undulating pattern. Mild cellular pleomorphism was identified, and no mitosis figures were observed. Alcian blue staining was negative for mucopolysaccharides, differing from Masson's trichrome staining, which widely stained the fibrocollagenous tissue blue. In view of these findings, the diagnosis of cutaneous fibroma was confirmed. Discussion: Cutaneous fibromas are benign neoplasms of fibrous tissue, and they are uncommon in cattle and may be associated with bovine papillomavirus and/or trauma. Although the origin of cutaneous fibroma is not clear, the present report stands out due to the large size of the tumor mass. The complete healing of the surgical wound, the absence of recurrence one year after surgery and the return of the animal to dairy production demonstrate that the surgical treatment was adequate. The macro- and microscopic characteristics of the cutaneous fibroma in this case corroborate with other cases reported in the literature. Large cutaneous fibroma is uncommon in bovines, and may hinder surgical excision and prolong healing time, as well as the complete recovery of the animal. Moreover, the differential diagnosis with other neoplasms of fibroblastic origin is relevant, especially for those with malignant biological behavior, such as fibrosarcoma and myxosarcoma.

Peripheral nerve sheath tumor in the upper eyelid in a dog

Background: Peripheral nerve sheath tumors are most commonly found on the head and neck regions of both dogs and people. Schwannomas are rarely observed in ophthalmic areas. When they occur, ocular Schwannomas are usually located in the orbit, uveal tract and conjunctiva. The occurrence of uveal schwannoma, a subset of PNST has been well documented in the veterinary literature. PNST has never been observed in the eyelids of dogs. Therefore, the present report aimed to describe the surgical treatment and outcome of a PNST located in the upper eyelid of a dog. Case: A 9-year-old, spayed female mixed-breed dog was referred for evaluation of a large mass involving the right upper eyelid for a duration of approximately one month. The inspection revealed sero-sanguinolent discharge and an oval-shaped mass occupying more than 70% of the right upper eyelid. A presumptive diagnosis of eyelid neoplasia was considered most likely. Excision of the entire mass with a 2 cm margin was performed. The third eyelid and dorso-medial bulbar conjunctiva were also removed. Upper eyelid reconstruction was performed based on a similar technique previously described in cats (lip-to-lid flap). As a result, neoplastic spindle cells exhibited immunoreactivity for S100 and intense cytoplasmic staining for vimentin, supporting the diagnosis of schwannoma. Fifteen days later, the margins of the subdermal pattern flap were healed and skin sutures were removed. On the last follow-up, 9 months post-surgery, the dog was visual, and the flap was well incorporated and covered the ocular surface. Ten months later, another large mass arising from the right inferior palpebral conjunctiva was observed. Once ultrasound revealed orbital invasion exenteration combined with orbitectomy were performed, and the defect was covered with an auricular axial pattern flap. The second tumor had the same histological and immunohistochemical characteristics of the first mass. Both tumors expressed Ki67; however, the PI in the second mass was higher (7.9%) than the first (3.4%). Discussion: Reported eyelid neoplasms in dogs include adenomas and adenocarcinomas of the meibomian glands, melanomas, fibroma, fibrosarcoma, histiocytoma, mastocytoma, lipomas, papillomas, and squamous cell carcinomas. To the author's knowledge, however, this is the first case description of a PNST affecting the eyelid in a dog. The histologic distinction between PNSTs and other spindle cell tumors, including myxosarcoma, fibrosarcoma, leiomyosarcoma, hemangiopericytoma, and melanoma can be challenging and requires immunohistochemical stainin. S100 is an acidic protein that identifies various nervous tissue cells, including Schwann cells, and the majority of canine PNSTs diffusely express this molecule. As in the case presented here, neoplastic cells of different ocular and adnexal structures were also positive for S100 and vimentin in all PNSTs previously reported in the veterinary literature. This is the first report of PNST affecting the eyelid in a dog. The lip-to-lid flap is a feasible technique to reconstruct the upper eyelid following wide surgical removal of a tumor in dogs. However, the authors suggest radical surgery combining orbitectomy, exenteration and a miocutaneous flap if PNST is diagnosed in the eyelids of dogs. They also caution once recurrence is possible and can be more aggressive.(AU)

Mixossarcoma esplênico em cão / Splenic myxosarcoma in a dog

Background: Myxosarcomas (MXS) are malignant mesenchymal neoplasms originated from mainly mucin producing fibroblasts than collagen. Despite malignant neoplasms, MXS is believed to have low metastase generation ability. Myxosarcomas reports in dogs are widespread, usually involving trunk and limbs subcutaneous tissue. The aim of this report is to describe clinical, pathological, and immunohistochemistry aspects of a rare case of splenic myxosarcoma in a dog.Case: A 10-year-old, intact male Basset Hound, weiging 25 kg, showing signals such apathy, dark soft-stooled stools, progressive thinning, and increasing abdominal enlargement, perceived three months ago was brought to clinical consultation. Physical examination showed extremely pale oral and ocular mucosas, in addition to mild dehydration (6%), 35.4°C rectal temperature, and a very bulging abdomen, with no fluids or gases, evidence at abdominal percussion. A complete blood count (CBC) revealed neutrophilic leukocytosis and anemia. Patient´s abdominal cavity ultrasound examination showed an heterogeneous mass, occupying large part of cavity, and apparently from spleen origin. A spleenic multilobulated mass measuring 25 x 12 x 20 cm was obtained after exploratory laparotomy. The mass showed predominantly soft consistency with some firm areas, and no visible mesentery or other abdominal organs adhesions. Mass and spleen histopathological examination were routinely processed for histological analysis with haematoxylin and eosin and alcian blue staining. In addition, fragments of the neoplasm were submitted to immunohistochemistry (IHC) which confirmed myxosarcoma diagnosis. The owner returned to hospital two months after, complaining for apathy, prostration, anorexia, and abdominal pain. A new ultrasound examination were suggestive of liver and kidneys neoplasms. The tutor opted for patient´s euthanasia. However, dog´s necropsy was not authorized...

Mixossarcoma esplênico em cão / Splenic myxosarcoma in a dog

Background: Myxosarcomas (MXS) are malignant mesenchymal neoplasms originated from mainly mucin producing fibroblasts than collagen. Despite malignant neoplasms, MXS is believed to have low metastase generation ability. Myxosarcomas reports in dogs are widespread, usually involving trunk and limbs subcutaneous tissue. The aim of this report is to describe clinical, pathological, and immunohistochemistry aspects of a rare case of splenic myxosarcoma in a dog.Case: A 10-year-old, intact male Basset Hound, weiging 25 kg, showing signals such apathy, dark soft-stooled stools, progressive thinning, and increasing abdominal enlargement, perceived three months ago was brought to clinical consultation. Physical examination showed extremely pale oral and ocular mucosas, in addition to mild dehydration (6%), 35.4°C rectal temperature, and a very bulging abdomen, with no fluids or gases, evidence at abdominal percussion. A complete blood count (CBC) revealed neutrophilic leukocytosis and anemia. Patient´s abdominal cavity ultrasound examination showed an heterogeneous mass, occupying large part of cavity, and apparently from spleen origin. A spleenic multilobulated mass measuring 25 x 12 x 20 cm was obtained after exploratory laparotomy. The mass showed predominantly soft consistency with some firm areas, and no visible mesentery or other abdominal organs adhesions. Mass and spleen histopathological examination were routinely processed for histological analysis with haematoxylin and eosin and alcian blue staining. In addition, fragments of the neoplasm were submitted to immunohistochemistry (IHC) which confirmed myxosarcoma diagnosis. The owner returned to hospital two months after, complaining for apathy, prostration, anorexia, and abdominal pain. A new ultrasound examination were suggestive of liver and kidneys neoplasms. The tutor opted for patient´s euthanasia. However, dog´s necropsy was not authorized...(AU)

Aspectos citológicos das principais neoplasias mesenquimais tegumentares em cães (canis familiares)

O presente estudo avaliou os achados citológicos de 55 casos diagnosticados histologicamente como fibroma, hemangioma, fibrossarcoma (FSA), mixossarcoma (MXS), tumor de parede perivascular (TPP), tumor da bainha de nervo periférico (TBNP), lipossarcoma (LPS) e hemangiossarcoma (HSA) cutâneos e subcutâneos caninos, com o objetivo de estabelecer possíveis direcionamentos diagnósticos. A celularidade moderada ou intensa esteve presente em 16,6, 72,2 e 50,0% das amostras benignas, de sarcoma de tecidos moles (STS) e HSA, respectivamente. O predomínio de células fusiformes a ovaladas ou ovaladas foi observado em 50,0; 80,9 e 87,5% das amostras benignas, de STS e HSA, respectivamente. A associação destes dois achados em uma mesma amostra foi observada em 0,0 e 55,6% dos casos benignos e de FSA/MXS/HSA, respectivamente. Alguns achados foram observados exclusivamente em determinadas neoplasias, como a presença de células cabeças de inseto e células coroa, observadas apenas nos TPPs e TBNPs; citoplasma com vacúolos lipídicos, somente nos LPSs, e figuras angioformativas, observadas apenas nas neoplasias vasculares (hemangioma e HSA). As figuras de mitose, binucleação e multinucleação foram observadas somente nos casos malignos, enquanto a presença de vasos sanguineos foi observada em 5,5; 42,9 e 31,3% das amostras benignas, de STS e HSA, respectivamente; e a presença de nucléolos múltiplos foi observada em 5,5; 14,3 e 62,5% dos mesmos respectivos grupos. Entretanto a ausência de importantes critérios de malignidade foi observada em uma proporção significativa dos casos malignos

The present study evaluated the cytological findings of 55 cases diagnosed histologically as fibroma, hemangioma, fibrosarcoma (FSA), myxosarcoma (MXS), perivascular wall tumor (TPP), peripheral nerve sheath tumor (TBNP), liposarcoma (LPS) and hemangiosarcoma (HSA) cutaneous and subcutaneous in dogs, with the objective of establishing possible diagnostic directions. Moderate or intense cellularity was present in 16.6, 72.2 and 50.0% of benign soft tissue sarcoma (STS) and HSA samples, respectively. The predominance of predominantly fusiform to oval or oval cells was observed in 50.0; 80.9 and 87.5% of benign STS and HSA samples, respectively. The association of these two findings in the same sample was observed in 0.0 and 55.6% of benign and FSA / MXS / HSA cases, respectively. Some findings were observed exclusively in certain neoplasms, such as the presence of insect head cells and crown cells, observed only in TPPs and TBNPs; lipid cytoplasm, only in LPSs and angioformative figures, observed only in vascular neoplasms (hemangioma and HSA). Mitosis, binucleation and multinucleation figures were observed only in malignant cases, while the presence of blood vessels was observed in 5.5; 42.9 and 31.3% of the benign samples, of STS and HSA, respectively; and the presence of multiple nucleoli was observed in 5.5; 14.3 and 62.5% of the same respective groups. However, the absence of important malignancy criteria was observed in a significant proportion of malignant cases.

Dificuldades no diagnóstico do mixossarcoma de vesícula urinária em cão / Challenges in diagnosing of canine myxosarcoma bladder

Tumores envolvendo o sistema urinário representam aproximadamente 2,4% das neoplasias emcães. Estudos revelam que, embora as neoplasias possam afetar qualquer parte do sistema urinário, oenvolvimento da bexiga é incomum e a inespecificidade dos sinais pode comprometer a suspeita inicial e odiagnóstico precoce. Apesar dos avanços na ultrassonografia e na citologia, nas ultimas décadas, algumasimprecisões ainda ocorrem. Esse trabalho descreve o acompanhamento e as dificuldades no diagnóstico de ummixossarcoma vesical raro em um cão, fêmea, da raça Maltês, com 11 anos de idade apresentando hiporexia,vômito e dor abdominal. Houve limitação no diagnóstico utilizando-se a ultrassonografia, sendo o examehistopatológico fundamental para conclusão do caso

Tumors in urinary system represent approximately 2.4% of neoplasms in dogs. Searches showthat although the tumors can affect any part of the urinary system, the involvement of the urinary bladder isuncommon and non-specificity of clinical signs may compromise the initial clinical suspicion and early accuratediagnosis of canine bladder tumor. Despite ultrasonography and citology advances over the past decades,inaccuracies in the evaluation of the urinary bladder still remain. This paper describes the monitoring anddifficulties in diagnosis of myxosarcoma bladder rare in a eleven-month-old female Maltese dog who hadappetite loss, vomiting and abdominal pain. There were limitations in the diagnosis using ultrasound, and thehistopathological examination was fundamental for case completing

Dificuldades no diagnóstico do mixossarcoma de vesícula urinária em cão / Challenges in diagnosing of canine myxosarcoma bladder

Tumores envolvendo o sistema urinário representam aproximadamente 2,4% das neoplasias emcães. Estudos revelam que, embora as neoplasias possam afetar qualquer parte do sistema urinário, oenvolvimento da bexiga é incomum e a inespecificidade dos sinais pode comprometer a suspeita inicial e odiagnóstico precoce. Apesar dos avanços na ultrassonografia e na citologia, nas ultimas décadas, algumasimprecisões ainda ocorrem. Esse trabalho descreve o acompanhamento e as dificuldades no diagnóstico de ummixossarcoma vesical raro em um cão, fêmea, da raça Maltês, com 11 anos de idade apresentando hiporexia,vômito e dor abdominal. Houve limitação no diagnóstico utilizando-se a ultrassonografia, sendo o examehistopatológico fundamental para conclusão do caso(AU)

Tumors in urinary system represent approximately 2.4% of neoplasms in dogs. Searches showthat although the tumors can affect any part of the urinary system, the involvement of the urinary bladder isuncommon and non-specificity of clinical signs may compromise the initial clinical suspicion and early accuratediagnosis of canine bladder tumor. Despite ultrasonography and citology advances over the past decades,inaccuracies in the evaluation of the urinary bladder still remain. This paper describes the monitoring anddifficulties in diagnosis of myxosarcoma bladder rare in a eleven-month-old female Maltese dog who hadappetite loss, vomiting and abdominal pain. There were limitations in the diagnosis using ultrasound, and thehistopathological examination was fundamental for case completing(AU)

Cutaneous myxosarcoma in a Syrian hamster (Mesocricetus auratus) / Mixossarcoma cutâneo em um hamster Sírio

The pathological findings in a 2-years-old Syrian hamster (Mesocricetus auratus) with a cutaneous myxosarcoma are described. Grossly, there was a large cutaneous mass in the right cervical region. Microscopical evaluation revealed a myxosarcoma characterized by pleomorphic, fusiform cells loosely arranged, randomly distributed, and presenting a moderate amount of basophilic amorphous stroma. There were hemorrhagic areas within the tumor. The basophilic amorphous stroma was positive to Alcian blue confirming the presence of a mucopolysaccharide matrix. Immunohistochemically, the neoplastic cells expressed vimentin, and were negative for cytokeratin or glial fibrillary acidic protein (GFAP).

São descritos os achados anatomopatológicos de um caso de mixossarcoma cutâneo em um Hamster Sírio de 2 anos de idade. Macroscopicamente, foi evidenciada um grande massa cutânea na região cervical lateral direita. A microscopia revelou a presença de um mixossarcoma caracterizado por células fusiformes pleomórficas, frouxamente arranjadas, distribuídas aleatoriamente e, apresentando quantidade moderada de substância basofílica amorfa no estroma e áreas hemorrágicas. O estroma basofílico amorfo foi positivo na coloração Alcian blue, confirmando a presença de matriz mucopolissacarídea. Na imunoistoquímica, as células neoplásicas expressaram vimentina e foram negativas para a marcação de citoqueratina e proteína ácida fibrilar (GFAP).

Diagnostic significance of mitotic index and AgNOR count in canine mammary tumours

The present study was designed to investigate the significance of mitotic index and AgNOR count in canine mammary tumours. Samples from 74 grossly suspected cases of bitches for mammary tumour were collected from different veterinary hospitals in 10% buffered formalin, of which 65 were confirmed as tumours on histopathological examination. Among them, 11 (16.92%) were benign and 54 (83.08%) were malignant tumours. Benign tumours included benign mixed mammary tumour (36.36%), fibroadenoma (27.27%), duct papilloma (18.18%) and simple adenoma (18.18%). The malignant mammary tumours comprised of papillary adenocarcinoma (27.78%), malignant mixed mammary tumour (25.92%), solid carcinoma (18.52%), squamous cell carcinoma (5.56%), fibrosarcoma (5.56%), infiltrative adenocarcinoma (3.7%), mucinous carcinoma (3.7%) and each (1.54%) of osteochondrosarcoma, carcinosarcoma, myxosarcoma, intraductal carcinoma and spindle cell carcinoma (malignant myoepithelioma). Mitotic index and AgNOR counts were significantly (P<0.05) differ for benign and malignant mammary tumours. Among malignant mammary tumours mitotic index ranged from 1.08 to 4.19 with solid carcinoma showing the highest index (4.197±1.570) and osteochondrosarcoma the lowest (1.08±0.0) while in benign mammary tumours, it ranged from 0.63 t0 0.9. AgNOR counts were significantly lower (2.57± 0.68) in benign mammary tumours than malignant (3.38±1.01). From this study it was concluded that mitotic index and AgNOR count was a good indicator of transformation of tumours towards the malignancy

Diagnostic significance of mitotic index and AgNOR count in canine mammary tumours

The present study was designed to investigate the significance of mitotic index and AgNOR count in canine mammary tumours. Samples from 74 grossly suspected cases of bitches for mammary tumour were collected from different veterinary hospitals in 10% buffered formalin, of which 65 were confirmed as tumours on histopathological examination. Among them, 11 (16.92%) were benign and 54 (83.08%) were malignant tumours. Benign tumours included benign mixed mammary tumour (36.36%), fibroadenoma (27.27%), duct papilloma (18.18%) and simple adenoma (18.18%). The malignant mammary tumours comprised of papillary adenocarcinoma (27.78%), malignant mixed mammary tumour (25.92%), solid carcinoma (18.52%), squamous cell carcinoma (5.56%), fibrosarcoma (5.56%), infiltrative adenocarcinoma (3.7%), mucinous carcinoma (3.7%) and each (1.54%) of osteochondrosarcoma, carcinosarcoma, myxosarcoma, intraductal carcinoma and spindle cell carcinoma (malignant myoepithelioma). Mitotic index and AgNOR counts were significantly (P<0.05) differ for benign and malignant mammary tumours. Among malignant mammary tumours mitotic index ranged from 1.08 to 4.19 with solid carcinoma showing the highest index (4.197±1.570) and osteochondrosarcoma the lowest (1.08±0.0) while in benign mammary tumours, it ranged from 0.63 t0 0.9. AgNOR counts were significantly lower (2.57± 0.68) in benign mammary tumours than malignant (3.38±1.01). From this study it was concluded that mitotic index and AgNOR count was a good indicator of transformation of tumours towards the malignancy (AU)

Mixossarcoma em mesentério de cão

Myxosarcoma is an unusual neoplasm in the dog, most seen in the skin, and seldom in the heart and in the liver. The authors describe a case of a 5-years old mongrel dog showing abdominal distension, weakness, and decreased appetite. An exploratory celiotomy showed a massive non-encapsulated nodular tumour, adhered on the mesentery, measuring 30cm in diameter. Histopatology identified the tumour as a myxosarcoma. There is not previous record of mesenteric myxosarcoma.

Mixossarcoma cutâneo em um Hamster Sírio / Cutaneous myxosarcoma in a Syrian hamster (Mesocricetus auratus)

São descritos os achados anatomopatológicos de um caso de mixossarcoma cutâneo em um Hamster Sírio de 2 anos de idade. Macroscopicamente, foi evidenciada um grande massa cutânea na região cervical lateral direita. A microscopia revelou a presença de um caso de mixossarcoma caracterizado por células fusiformes pleomórficas, frouxamente arranjadas, distribuídas aleatoriamente e, apresentando quantidade moderada de substância basofílica amorfa no estroma e áreas hemorrágicas. O estroma basofílico amorfo foi positivo na coloração Alcian blue, confirmando a presença de matriz mucopolissacarídea. Na imunoistoquímica, as células neoplásicas expressaram vimentina e foram negativas para a marcação de citoqueratina e proteína ácida fibrilar (GFAP).

The pathological findings in a 2-years-old Syrian hamster (Mesocricetus auratus) with a cutaneous myxosarcoma are described. Grossly, there was a large cutaneous mass in the right cervical region. Microscopical evaluation revealed a myxosarcoma characterized by pleomorphic, fusiform cells loosely arranged, randomly distributed, and presenting a moderate amount of basophilic amorphous stroma. There were hemorrhagic areas within the tumor. The basophilic amorphous stroma was positive to Alcian blue confirming the presence of a mucopolysaccharide matrix. Immunohistochemically, the neoplastic cells expressed vimentin, and were negative for cytokeratin or glial fibrillary acidic protein (GFAP).

Mixossarcoma cutâneo em um Hamster Sírio / Cutaneous myxosarcoma in a Syrian hamster (Mesocricetus auratus)

São descritos os achados anatomopatológicos de um caso de mixossarcoma cutâneo em um Hamster Sírio de 2 anos de idade. Macroscopicamente, foi evidenciada um grande massa cutânea na região cervical lateral direita. A microscopia revelou a presença de um caso de mixossarcoma caracterizado por células fusiformes pleomórficas, frouxamente arranjadas, distribuídas aleatoriamente e, apresentando quantidade moderada de substância basofílica amorfa no estroma e áreas hemorrágicas. O estroma basofílico amorfo foi positivo na coloração Alcian blue, confirmando a presença de matriz mucopolissacarídea. Na imunoistoquímica, as células neoplásicas expressaram vimentina e foram negativas para a marcação de citoqueratina e proteína ácida fibrilar (GFAP).

The pathological findings in a 2-years-old Syrian hamster (Mesocricetus auratus) with a cutaneous myxosarcoma are described. Grossly, there was a large cutaneous mass in the right cervical region. Microscopical evaluation revealed a myxosarcoma characterized by pleomorphic, fusiform cells loosely arranged, randomly distributed, and presenting a moderate amount of basophilic amorphous stroma. There were hemorrhagic areas within the tumor. The basophilic amorphous stroma was positive to Alcian blue confirming the presence of a mucopolysaccharide matrix. Immunohistochemically, the neoplastic cells expressed vimentin, and were negative for cytokeratin or glial fibrillary acidic protein (GFAP).

Mixossarcoma cutâneo em um Hamster Sírio / Cutaneous myxosarcoma in a Syrian hamster (Mesocricetus auratus)

São descritos os achados anatomopatológicos de um caso de mixossarcoma cutâneo em um Hamster Sírio de 2 anos de idade. Macroscopicamente, foi evidenciada um grande massa cutânea na região cervical lateral direita. A microscopia revelou a presença de um caso de mixossarcoma caracterizado por células fusiformes pleomórficas, frouxamente arranjadas, distribuídas aleatoriamente e, apresentando quantidade moderada de substância basofílica amorfa no estroma e áreas hemorrágicas. O estroma basofílico amorfo foi positivo na coloração Alcian blue, confirmando a presença de matriz mucopolissacarídea. Na imunoistoquímica, as células neoplásicas expressaram vimentina e foram negativas para a marcação de citoqueratina e proteína ácida fibrilar (GFAP).

The pathological findings in a 2-years-old Syrian hamster (Mesocricetus auratus) with a cutaneous myxosarcoma are described. Grossly, there was a large cutaneous mass in the right cervical region. Microscopical evaluation revealed a myxosarcoma characterized by pleomorphic, fusiform cells loosely arranged, randomly distributed, and presenting a moderate amount of basophilic amorphous stroma. There were hemorrhagic areas within the tumor. The basophilic amorphous stroma was positive to Alcian blue confirming the presence of a mucopolysaccharide matrix. Immunohistochemically, the neoplastic cells expressed vimentin, and were negative for cytokeratin or glial fibrillary acidic protein (GFAP).