Ultrastructure of canine carotid body and aortic body tumors. Comparison with tissues of thyroid and parathyroid origin

An atypical case of recurrent carotid body carcinoma in a young adult dog: Histopathological, immunohistochemical and electron microscopic study

A 3.5-year-old female Chihuahua was presented with complaint of neck pain, intermittent cough and dysphagia. Physical examination and diagnostic imaging of neck region revealed a solid and highly vascularized mass involving the retropharyngeal region. Histologically, the mass showed an atypical zellballen pattern which comprised of high density of type I chief cells with high nuclear cytoplasmic ratio and separated by delicate fibrovascular stroma. Immunoreactivity for neuroendocrine markers was diffusely positive in cytoplasm of tumor cells. Disseminated tumor emboli in external jugular vein were detected 6 months after initial surgery. An electron microscopic study revealed numerous electron-dense intracytoplasmic neurosecretory granules. Based on these findings, carotid body carcinoma was diagnosed.

Multiple Osseous Metastases of a Carotid Body Tumor in a Dog

Metastasis of malignant carotid body tumor to multiple bones was detected in a 13-year-old female Siberian husky dog. Radiographs exhibited an abnormal mass in the retropharyngeal site and osteolytic lesions in the vertebral bodies, spinous process, tibia, and ribs. At necropsy, multiple masses were observed in the bones as well as at the dorsal area of the retropharynx. Histologically, the tumor cells, arranged in sheets and clusters, had eosinophilic finely granular cytoplasm. Immunohistochemistry showed the tumor cells were positive for neuron-specific enolase and synaptophysin. Electron microscopy demonstrated a number of dense membrane-bound granules in the cytoplasm of the tumor cells. Based on these findings, this case was diagnosed as multiple bone metastases of a malignant carotid body tumor. Spinal cord damage induced by the tumor mass was the cause of the hind limb paralysis of the present dog.

Unusual metastasis of malignant aortic body tumor to multiple bones in a dog

Unusual metastasis of malignant aortic body tumor to multiple bones was detected in a 5-year-old female English Setter dog. Radiographs exhibited an abnormal mass in the base of heart and osteolytic lesions in the bodies of T11 and L2 vertebrates, body of right femur, right proximal humoral epiphysis and infraspinous fossa near to the neck of right scapula. At necropsy, multiple tumor masses of various sizes were observed also in the bones as well as the heart base and tracheobronchial lymph node. Tumor masses of L2 and T11 protruded into the vertebral canal and compressed corresponding sites of spinal cord, leading to paraplegia. Histopathologically, the tumor cells, arranged in sheets or nests, were polyhedral, lightly eosinophilic, finely granular cytoplasm with mostly round to oval nucleus and had scattered bizarre giant cells. Ultrastructural study revealed the characteristic findings that tumor cells contained a large number of small, electron-dense, membrane-limited secretory granules in cytoplasm. This is thought to be an extremely rare case having multiple bone metastases of a malignant aortic body tumor.

Overview of structural and functional lesions in endocrine organs of animals

The objective of this review is to summarize the pathogenic mechanisms responsible for perturbations of endocrine function and development of structural lesions that result in important diseases in domestic and laboratory animals. For each major category, several specific disease problems have been selected to illustrate the functional and morphologic lesions that are characteristic for either a naturally occurring endocrinopathy or endocrine disturbances induced by the administration of large doses of xenobiotic chemicals. The major pathogenic mechanisms responsible for disruption of endocrine function include primary hyperfunction, secondary hyperfunction, primary hypofunction, secondary hypofunction, endocrine hyperactivity secondary to other conditions, hypersecretion of hormones by nonendocrine tumors, failure of target cells to respond to a hormone, failure of fetal endocrine function, abnormal degradation (increased or decreased rate) of hormone, and iatrogenic syndromes of hormone excess (direct and indirect). Disorders of the endocrine system are encountered in a wide variety of domestic and laboratory animal species and often present challenging diagnostic problems. The development of proliferative lesions, usually hyperplasia and benign tumors, in endocrine organs and hormone-responsive tissues are common findings in chronic studies with high doses of many nongenotoxic xenobiotic chemicals administered to sensitive rodent species and may have limited significance for human safety assessment.

Carotid body tumors in the dog. Eleven cases (1978-1988)

Case records of 11 dogs with histologically confirmed carotid body tumors were reviewed. Surgical excision had been attempted in ten dogs with carotid body tumors, and one dog had been euthanatized at diagnosis. There were no intraoperative deaths but perioperative mortality was 40%. Horner's syndrome and laryngeal paralysis were the most common postoperative morbidities. The median survival time after surgery alone in the four dogs that survived the perioperative period was 25.5 months (range, 12-45 months). Two dogs treated with postoperative radiation therapy had survival times of 6 and 27 months. Of the six dogs surviving the perioperative period, two dogs are still alive at 19 and 32 months postoperatively. Of the four dogs that died, one was euthanatized 12 months postoperatively for nontumor-related causes. The remaining three dogs died of distant metastases. The carotid body tumors studied were characterized by local tissue invasion, neurovascular complications after therapy, and a propensity to metastasize to multiple sites in the body.

The effects of xenobiotics on the structure and function of thyroid follicular and C-cells

The mammalian thyroid gland is composed of 2 distinct endocrine cell populations concerned with the synthesis of 2 different classes of hormones. Follicular cells secrete the metabolically active iodothyronines whereas the C-(parafollicular) cells are concerned with the production of calcitonin, a hormone that influences blood levels of calcium and phosphorus, and bone cell metabolism. The synthesis of metabolic thyroid hormones is different than in other endocrine glands because the final assembly of hormone occurs within the follicular lumen. This extracellular synthesis of thyroid hormones is made possible by thyroglobulin, a glycoprotein synthesized by follicular cells. The secretion of thyroid hormones under the influence of pituitary thyrotrophin (TSH) from stores in the luminal colloid is initiated by elongation of microvilli and formation of pseudopods. FD&C Red No. 3 is a tetraiodinated derivative of fluorescein which in lifetime studies increases the incidence of thyroid follicular cell adenomas in male Sprague-Dawley rats. The striking changes in circulating levels of thyroid hormones and morphologic evidence of follicular cell stimulation are the result of alterations in the peripheral metabolism of thyroxine. An inhibition by FD&C Red No. 3 of 5'-deiodinase in the liver and kidney would explain the lower serum triiodothyronine (T3) levels. The pituitary, sensing the lowered circulating levels of T3, increased the secretion of thyroid stimulating hormone which resulted in the morphologic evidence of follicular cell stimulation in the long-term studies. Other xenobiotics increase the incidence of thyroid tumors in rodents by a direct effect on the thyroid gland to disrupt 1 of 3 or more possible steps in the biosynthesis of thyroid hormones. Physiologic perturbations alone, such as iodine deficiency or partial thyroidectomy, can disrupt thyroid hormone economy in rodents and, if sustained, increase the development of thyroid tumors. The wide variety of drugs, chemicals, and physiologic perturbations which increase thyroid tumor development appear to act through a secondary (indirect) mechanism to promote tumor development by causing a long-standing hypersecretion of thyroid stimulating hormone. Nodular and/or diffuse hyperplasia of C-cells occurs with advancing age in many strains of laboratory rats and in response to long-term hypercalcemia in certain animal species and human beings. Focal or diffuse hyperplasia often precedes the development of C-cell neoplasms. Radiation and the feeding of diets high in vitamin D resulting in hypercalcemia have been reported to increase the incidence of C-cell tumors in rats.

Pathologic features of abdominal and thoracic paragangliomas in F344/N rats

Seventeen paragangliomas were identified in a retrospective review of 200 NTP/NCI carcinogenicity studies in F344/N rats that served either as control or treated animals. Most tumors were grossly visible and located in the retroperitoneum adjacent to the vertebrae and aorta near the kidneys. Three microscopically detected paragangliomas were found at the base of the heart. Microscopically, neoplastic cells were in nests separated by reticulin fibers and capillaries. Argyrophil granules were in the cytoplasm of the retroperitoneal and mediastinal paravertebral tumors. Dense granules were found in the one tumor examined ultrastructurally. Some tumors had areas of necrosis and tumor emboli were present in the lumen of the abdominal aorta and vena cava adjacent to the tumor with metastases present in pulmonary vessels. The incidence of retroperitoneal neoplasms was 3 times more frequent in male than in female F344/N rats.

Neoplastic diseases of the thorax

Thoracic neoplasia comprises a heterogeneous group of diseases, many of which are distinctly uncommon in veterinary medicine. These diseases often present the clinician with diagnostic and therapeutic challenges. Careful diagnostic work-up and staging are essential for consideration of therapeutic options and formulation of prognosis. Neoplastic diseases of the thorax are classified here as tracheal tumors, primary lung tumors, nonrespiratory intrathoracic tumors, and thoracic wall tumors.

Aortic body tumour with adjacent ectopic thyroid tissue in a dog

A 12-year-old neutered male Husky dog had a neoplasm at the base of the heart which did not invade surrounding tissues. Microscopically, the neoplasm was composed of nests and sheets of polyhedral cells subdivided into lobules by trabeculae of fine fibrovascular stroma. Adjacent to the neoplasm was a rim of ectopic thyroid tissue that appeared histologically normal. The possible differential diagnoses for the neoplasm were aortic body tumour, ectopic thyroid tumour and ectopic parathyroid tumour; the ultrastructural characteristics revealed it to be an aortic body tumour.

Laryngeal neuroendocrine tumour with features of a paraganglioma, intracytoplasmic lumina and acinar formation

A supraglottic laryngeal neuroendocrine tumour in a 71-year-old female is presented. In addition to the typical features of extra-adrenal paragangliomas it showed unusual, numerous intracytoplasmic lumina and occasional true acini with accumulation of alcian blue and PAS positive secretory product in them which led originally to an erroneous diagnosis of metastatic adenocarcinoma. Ultrastructurally, the tumour was composed of light and dark chief cells containing varying numbers of dense-core secretory granules. Intracytoplasmic lumina and true acini contained microvilli with glycocalyceal material and varying amounts of membranous and amorphous material, possibly secreted via small, smooth-surfaced cytoplasmic vesicles but typical mucin granules were not seen. These features have not been previously described in laryngeal paragangliomas but are seen in endocrine tumours of other sites and have been used as an argument in favour of an endodermal rather than ectodermal origin for endocrine cells in those sites. Laryngeal paragangliomas are often malignant and the presence of spasmodic pain appears to be the most reliable indication of possible malignancy, histological criteria being as yet poorly defined.

Basal cell adenoma with parallel tubules in stromal cells of the parotid gland

A case of basal cell adenoma in the right parotid region of a 51 years old male was reported. The tumor measured 2.5 cm x 3 cm, was spherical and covered with a fibrous capsule. Histologically, it was a tubular monomorphic adenoma with scant edematous interstitial tissue. The stromal cells stained positively by the PAP method using anti-S-100 protein serum. Electron microscopically, the tumor cells forming tubular had many microvilli at the luminal surface, many filaments in the cytoplasm and well developed desmosomes in the intercellular junctions. Ordinary intracellular organelles of the tumor cells were small in number, and their nuclei were oval with shallow indentation. In the dilated rough endoplasmic reticulum of the stromal cells, many straight parallel tubules were found. The tubules measured from 15 nm to 25 nm thick and 3.5 micrometers long in the longitudinal sections and from 25 nm to 30 nm in diameter with electron lucent core and poor coat in the cross sections. Other cell organelles of the stromal cells were small in number, and filaments and dense attachments were found in the ectoplasm. Around the stromal cells there was a discontinuous basement membrane.

Ectopic thyroid carcinoma with metastases in a beagle dog

A 10.25-year-old female beagle had an invasive neoplasm at the base of the heart which metastasized to the lungs, pancreas, and kidney. The neoplasm in these locations was composed of clusters of polyhedral cells surrounded by fine fibrovascular stroma. The differential diagnoses were malignant chemodectoma, ectopic parathyroid carcinoma, and ectopic thyroid carcinoma. Based on ultrastructural features, this tumor was an ectopic thyroid carcinoma.

Aortic body tumours and hyperplasia in the rat

The histologic features of aortic body neoplasia, hyperplasia, and normal aortico-pulmonary paraganglia were described for a series of 56 rats of several strains. Argyrophilic cytoplasmic granules were demonstrated in chief cells of the aortic body lesions, and electron microscopic examination disclosed the presence of electron-dense, membrane-bound granules in these cells. In a series of ageing rats, hyperplasia and neoplasia of the aortico-pulmonary paraganglia occurred more frequently in female WAG/Rij rats than in males of that strain, and more frequently than in males and females of the BN/Bi strain or of the (WAG X BN)F1 hybrid. No apparent causal relationship to chronic hypoxia could be shown, in that no correlation between the development of aortic body neoplasia or hyperplasia and cardiopulmonary disease was found. Aortic body lesions did not appear to occur as part of a multiple endocrinopathy syndrome, although hyperplasia and neoplasia of various endocrine organs occurred relatively frequently in the WAG/Rij strain.

Aortico-pulmonary paraganglioma: report of a case with ultrastructural study and review of the literature

The light microscopic and ultrastructural features of an aortico-pulmonary paraganglioma (A-PP) are presented. The tumor was characterized by organoid clustering of neoplastic chief cells to form Zellballen. Argyrophilic granules were demonstrated within chief cell cytoplasm using a modified Grimelus technique. Ultrastructurally, three distinct cell types were present within the tumor: endothelial cells, pericytes and neoplastic chief cells. Membrane-bound neurosecretory granules were present and measured 100 to 2000 nm in diameter. "Light" and "dark" chief cells were less distinct than previously reported in other head and neck paragangliomas. Analysis of the 36 documented A-PP reported in the English literature reveals that the tumor has been either incompletely excised or has been considered unresectable in one-third of the cases. The reported surgical mortality is 9%, or approximately equal to the incidence of malignant behavior. The treatment of choice is surgical resection but when this is not possible, radiation may be a useful adjunct in therapy.

Mediastinal parathyroid adenocarcinoma in a dog

A tumor in the anterior mediastinum was found in an adult male German Shorthaired Pointer. The dog presented with hypercalcemia that varied with the removal and recurrence of the tumor. The neoplasm was characterized by an encapsulated multilobed grey-white soft mass with stroma, and the recurrent tumor infiltrated veins and the heart. The tumor consisted of groups of clear cells with well outlined cytoplasmic boundaries separated by thin vascular stroma. These cells had few organelles, scattered clumps of glycogen, clear cytosol and prominent infolding and interdigitating plasma membranes and desmosomes. The clinical, light and electron microscopic features were consistent with a functional neoplasm of parathyroid tissue origin.