Thymolipoma in a cat

Thymolipomas are rare benign thymic neoplasms recognised in humans, composed of mature adipose tissue and thymic tissue. An 8-year-old male domestic shorthair cat presented with anorexia, lethargy and vomiting secondary to the development of a thoracic effusion and an anterior mediastinal tumoral mass with fatty appearance. Histologically, the mass consisted of adipose tissue containing numerous cords and nests of cortical and medullary thymic tissue. No signs of thymic epithelial or lymphoid neoplastic proliferation were detected. The findings in this case are remarkably similar to the macroscopic and histological features of thymolipoma in humans.     

Ectopic cervical thymic carcinoma in a dog

A 10-year-old male German shepherd dog was referred for evaluation of a cranial cervical mass causing progressively worsening respiratory distress. A fine-needle aspirate of the mass was obtained and the cytology results were compatible with a carcinoma. The dog underwent chemotherapy without clinical improvement and was ultimately euthanased because of clinical deterioration. At post-mortem examination, an irregular multi-lobated mass in the cranial cervical region was observed causing ventro-lateral tracheal deviation. Histopathology and immunohistochemistry revealed a mixed population of CD3 lymphocytes and macrophages in an exuberant fibrous stroma, associated with dispersed cytokeratin-positive epithelial cells with marked eosinophilic cytoplasm. Some of the epithelial cells were arranged in concentric clusters that were interpreted as Hassall's corpuscles. Histopathological examination of the thyroid gland revealed several neoplastic emboli composed of epithelial cells similar to those observed in the cervical mass. To the authors' knowledge, this is the first report of an ectopic cervical thymic carcinoma in a dog.     

Angiolipomatous tumors in dogs and a cat

Variants of lipoma are uncommon, although fibrolipoma and infiltrative lipoma have been well documented. This report describes two cases of rare angiolipoma in dogs and the first documentation of angiofibrolipoma and infiltrating angiolipoma in a cat and a dog, respectively. Tumors were solitary, and most were located on the thorax of middle-aged patients. Angiolipomas were composed of mature adipose tissue mixed with variable numbers of blood vessels. In addition to the adipose and vascular components, the angiofibrolipoma contained bundles of collagenous connective tissue. The infiltrative angiolipoma had a primary mass external to the muscle and was histologically similar to a mixed intramuscular hemangioma that was confined to the muscle. Both disrupted bundles of striated muscle and were associated with segmental degeneration and loss of myofibers.     

Synovial Hemangioma in a Dog

Objective— To report arthroscopic diagnosis and treatment of synovial hemangioma in a dog.
Study Design— Case report.
Animal— Standard Poodle (8-year-old neutered male).
Methods— A soft tissue density mass observed radiographically in the left stifle joint of a dog with a 2-month history of recurrent lameness, hemarthrosis, and a slight cranial drawer sign, was located by diagnostic arthroscopy and surgically excised via arthrotomy.
Results— Histologic evaluation revealed tissue composed of variably sized cavernous vascular spaces filled with erythrocytes that were considered compatible with synovial hemangioma.
Conclusions— In this dog, synovial hemangioma evident as a soft tissue mass on radiographs was associated with chronic lameness and hemarthrosis, and resolved with surgical excision.
Clinical Relevance— Synovial hemangioma, although seemingly rare in dogs, should be considered in the differential diagnosis for nontraumatic, recurrent lameness, and unresponsive to anti-inflammatory therapy when there is a circumscribed intracapsular soft tissue mass evident radiographically together with hemarthrosis.     

Acquired myasthenia gravis associated with a non-invasive thymic carcinoma in a dog

An 8 1/2-year-old neutered male Beagle was diagnosed with acquired myasthenia gravis associated with a non-invasive thymic carcinoma. The thymic mass was surgically excised and the dog was treated with pyridostigmine, prednisolone and azathioprine. Serial acetylcholine receptor antibody titres were increased initially but slowly declined to normal values over a period of 24 weeks. Improved exercise tolerance was seen following therapy, however, oesophageal dysfunction persisted. The dog was euthanased 26 weeks after initial presentation due to a complicating illness. A necropsy showed no regrowth or metastasis of the thymic carcinoma.     

Primary pulmonary chondrosarcoma in a dog.

Extraosseous chondrosarcomas are uncommon in the dog, and those originating in the lung are rare. This report presents a 9-year-old Beagle dog with a pulmonary mass which caused depression, fever, tachypnea, cough, and laboratory abnormalities. The mass was composed predominantly of chondroid tissue, and was histologically diagnosed as chondrosarcoma.     

Adrenal myelolipoma in a dog

Abdominal ultrasound examination in an 11-year-old, intact, female Labrador dog with hepatic disease revealed a nodular swelling of the left adrenal gland. Hyperadrenocorticism was suspected, but endocrine tests were negative. At the owner's request, an adrenalectomy was performed. Grossly, a nodular mass protruded from the external surface of the left adrenal gland and in cut section was hemorrhagic and effaced the cortical and medullary regions. Histologic examination revealed a cortical neoplasm with medullary involvement. The mass was composed of well-differentiated adipose cells, megakaryocytes, hematopoietic cells, and macrophages containing hemosiderin deposits. A diagnosis of cortical adrenal myelolipoma was made.     

Peripheral nerve sheath tumor of the diaphragm with osseous differentiation in a one-year-old dog.

A 12-month-old, spayed female German shepherd dog was referred to the Veterinary Teaching Hospital for repair of a diaphragmatic hernia. Abdominal exploration revealed an intact diaphragm, but thoracic exploration revealed a large mass originating from the diaphragm. Resection of the mass was incomplete and required reconstruction of the diaphragm. On histopathology, the mass was composed mainly of spindle-shaped cells with occasional areas of osseous and chondroid tissue. The tumor was diagnosed as a peripheral nerve sheath tumor (PNST) with chondro-osseous differentiation. The dog was released four days after surgery; however, she began having difficulty breathing seven days after discharge, and the owners elected euthanasia. A necropsy was not performed. This is the first known report of a PNST originating in the diaphragm of a dog.     

Infiltrative lipoma in cervical bones in a dog

A 4-year-old, neutered male Maltese presented with a 2-month history of right hemiparesis. The radiographic findings revealed bone lysis, and sclerotic changes in the right section of the fifth and sixth cervical bones with a mild radiolucent mass around the lesion. The magnetic resonance imaging revealed a hyperintense mass located in the region extending from the muscles to the bones and compressing the spinal cord. The mass was removed via a hemilaminectomy in the cervical area using the ventral and dorsal approach, and a histological examination confirmed that it was adipose tissue. An infiltrative lipoma was diagnosed based on these findings. The dog has ambulated normally for 24 months since undergoing surgery.     

Lacrimal pseudotumour in a young bull terrier

An inflammatory mass arising from the lower lacrimal canaliculus of unknown cause is reported in a dog. A 10-month-old Staffordshire bull terrier was presented with a history of epiphora and a red mass protruding from the left lower lacrimal punctum. The tissue was removed and histopathological examination of the lesion revealed a mass of highly vascularised granulation tissue with areas of epithelial ulceration and multiple stromal haemorrhages. Fibrosis and collagen deposition were evident as was a cellular infiltrate composed primarily of neutrophils and plasma cells. Regrowth necessitated further attempts at complete excision before a permanent cure was achieved.     

Anatomic location and age-related changes in the chinchilla thymus

Thymuses of chinchillas varying from 2 weeks to 8 years of age were studied grossly and histologically and were determined to be entirely intrathoracic. Histologically, the amount of actual thymic tissue in the older chinchillas appeared to be less than that in the younger chinchillas. Lymphocyte concentration within medullary centers of the older chinchillas was significantly (P less than 0.05) less than that of the younger animals. Lymphocytopoietic activity was evident in the oldest animals studied. Body weight and thymic mass (thymus plus adipose tissue) weight were greater (P less than 0.05) in the older chinchillas.     

Uterine angiolipoleiomyoma in a dog.

An 11-year-old crossbred Pomeranian bitch displayed a large intramural, well-delineated uterine mass in one horn, near the junction with the uterine body. The mass was composed largely of mature adipose tissue, smooth muscle cells singly and in small clusters, anomalous medium-size and large arteries, and multifocal islands of cartilaginous and osseous tissues. Smooth muscle cells stained positively for desmin, and adipocytes and chondrocytes were positive for S-100 protein. This tumor has histologic and immunohistochemical features compatible with human uterine angiolipoleiomyoma, a rare tumor that has never been reported in the veterinary literature. This benign tumor is believed to be of a choristomatous nature.     

Spontaneous necrotizing sialometaplasia of the submandibular salivary gland in a Beagle dog

A single mass was found on the left submandibular salivary gland at necropsy of a 15-month-old male commercially bred laboratory Beagle dog from a control dose group from a repeat toxicity study. Microscopically, the mass was composed of a well-demarcated area of coagulative necrosis surrounded and separated from the normal salivary gland tissue by a thick fibrovascular capsule. Necrosis was admixed with areas of hemorrhage, fibrin, edema, fibrinoid necrosis of the vascular tunica media, and thrombosis of small and large vessels. Within the necrotic tissue, there was marked ductal hyperplasia, and squamous metaplasia of duct and acinar epithelium. The mass was diagnosed as necrotizing sialometaplasia of the submandibular gland. Hyperplastic ductal elements and squamous metaplasia can be mistaken microscopically with squamous cell carcinoma. Therefore, pathologists should be aware of this lesion as to avoid errors in the diagnosis of this benign pathologic condition.     

Calcifying aponeurotic fibroma on the paw in a dog

A 12-year-old, spayed female, Maltese dog with a round and firm mass on the dorsal part of the left rear paw and a cervical mass was brought to the clinic. The paw mass was contiguous to the adjacent tendon; it was composed of neoplastic mesenchymal cells and had scattered foci of calcification with chondroid differentiation microscopically. The neoplastic cells were positive for vimentin and S100, but negative for desmin and smooth muscle actin. Microscopic features and immunohistochemistry results were consistent with calcifying aponeurotic fibroma (CAF). The cervical mass was composed of polygonal cells forming acini with marked anisocytosis and anisokaryosis and diagnosed as thyroid follicular carcinoma. No recurrence or metastasis occurred during follow-up. To the best of our knowledge, this is the first case of canine CAF with features identical to its human counterparts.Key clinical message:This report describes the rare case of calcifying aponeurotic fibroma on the paw in a dog. This is apparently the first case in the veterinary literature with identical clinical and pathological features to the human counterpart.     

Ureteral obstruction and hydronephrosis in a cat associated with retroperitoneal infarction

A 9-month-old cat was presented for routine vaccination before rehoming. Physical examination revealed a palpable mass in the cranial abdomen. The right kidney was severely enlarged (6cmx4cm) on plain abdominal radiographs, and failed to opacify normally during intravenous urography. Ultrasonography demonstrated a hydronephrotic right kidney. During exploratory coeliotomy, a retroperitoneal mass was identified, adherent to the caudal edge of the right kidney, enveloping the ureter and blocking urine outflow. The ureter caudal to the mass was of normal size. Right ureteronephrectomy was performed; the mass was subsequently freed from adhesions to the caudal vena cava and sublumbar muscles and excised. Histopathological examination revealed the mass to be composed of both normal and necrotic adipose tissue and fibrous tissue surrounding the ureter and a thrombosed, recanalised vessel. This appearance was consistent with an area of infarction and fibrosis with obstruction of the ureter. The cat was clinically well 3 months postoperatively.     

Recurrent bilateral exophthalmos associated with metastatic thymic carcinoma in a pet rabbit

A five-year-old, castrated, male chinchilla rabbit was presented for evaluation of recurrent bilateral exophthalmos. Besides a transient and stress-related exophthalmos with protrusion of both third eyelids, the ophthalmological examination was unremarkable. Plain radiography of the thorax revealed a large precardial mass of soft tissue density. Cytological preparations from the thoracic mass were dominated by small, mature lymphocytes with approximately 10 to 20 per cent lymphoblasts. Computed tomography of the head showed a symmetrical laterodorsal deviation of both eyes without evidence of retrobulbar masses. On necropsy a large cystic mass was present in the cranial thorax associated with severe hydrothorax, hydropericardium and ascites. Histology identified the precardial mass as thymic carcinoma with metastases in the kidneys. This case illustrates the difficulty of diagnosing thymic tumours based on cytological or histological features of the primary tumour alone. To the authors' knowledge, this is the first case of recurrent bilateral exophthalmos associated with a metastatic thymic carcinoma in a pet rabbit.     

Infiltrative angiolipoma of the parotid salivary gland in a dog

Solitary benign angiolipoma and infiltrative angiolipoma are rare tumours in dogs. Angiolipomata can be distinguished histologically from lipomata by the large number of tightly packed blood vessels seen between the adipocytes with multiple fibrin thrombi occupying some of the vessels' lumens. The dog presented with a solitary slow-growing mass in the cervical region. Histopathology revealed multifocal to coalescing single or clusters of blood-filled vessels lined by flattened endothelial cells with narrow, elongated, basophilic nuclei. These regions were embedded in adipose tissue with multifocal areas of intervascular remnants of differentiated serous salivary glandular tissue with multifocal small ducts. Fibrin thrombi occupied a few of the vessel lumens. A histological diagnosis of infiltrative angiolipoma was made. On computed tomography, the mass was bilobed with a suspected primary component involving the right parotid gland which was grossly enlarged. The mass had a slightly hypoattenuating mottled to lobulated appearance with a few hyperattenuating mineralised specks throughout. Hounsfield units of the mass ranged between 40 and 45, which was less than the 60-65 of the contralateral salivary glands and cranial musculature. Post contrast images showed no contrast enhancement of 90% of the mass with only a band of peripheral contrast uptake of the affected lateral lobe.     

Vaginal Neurofibroma in a Hysterectomized Poodle Dog

A 15‐year‐old, spayed, female poodle dog was presented for evaluation of a mass of tissue prolapsed from the vulva. The dog had been hysterectomized when it was 5 years old. A vaginal mass had been removed approximately 10 months before presentation. Haematological and serum biochemistry analyses demonstrated mild leucocytosis and glycaemia. A vaginal smear was predominantly made up of parabasal cells and intermediate cells with no neoplastic cells. Thoracal and abdominal radiographic findings were unremarkable. The ovaries could not be identified using abdominal ultrasonography. A midline exploratory laparotomy identified both ovaries that were surgically excised. The vaginal mass was also removed following an episiotomy procedure. Histopathological examination of the mass demonstrated that it was a neurofibroma. Both ovaries had cystic changes. Four months after the surgery, the owner reported that the dog was clinically normal. To the authors’ knowledge, this is the first reported case of a vaginal neurofibroma after an incomplete ovariohysterectomy in the dog.     

Congenital thymic aplasia in a Holstein-Israeli female calf

An unusual case of congenital thymic aplasia in a Holstein-Israeli female calf is described. The most prominent clinical findings were diarrhoea and weakness. At necropsy, the only significant pathological finding was the marked decrease in thymus size. Histologically, this organ was composed of loose connective tissue in which a few lymphocytes were scattered randomly.     

Cervical teratoma in a dog

A young adult boxer dog was examined for a painless swelling in the left cranial cervical area that was refractory to antibiotic therapy. Ultrasound examination revealed a hypoechoic mass abutting the rostrolateral aspect of the left mandibular salivary gland. The cystic mass was excised and was found to extend through the capsule of the salivary gland and appeared to be confluent with the glandular tissue at this point. Histopathological examination of the excised tissue demonstrated tissue from all 3 germinal layers. There was no indication of malignancy and the mass was diagnosed as a benign cervical teratoma. Hypotheses regarding the origin of teratomas in general are discussed and the origin of the teratoma in this case is suggested.