Cases with manifestation of chemodectoma diagnosed in dogs in Department of Internal Diseases with Horses, Dogs and Cats Clinic, Veterinary Medicine Faculty, University of Environmental and Life Sciences, Wroclaw, Poland.

In the period of 3 years, 9 tumours of chemodectoma were supravitally diagnosed and histopathologically verified in dogs. In this period 15 351 dogs were admitted to the Clinic of Dogs and Cats and 2 145 dogs were examined in the cardiological outpatient clinic for dogs. This tumour is located in a typical place--at the base of the heart. Most frequently the tumour manifested in older boxers. Only in one case such a tumour was diagnosed in another breed of dogs. The tumours ranged in size between 3 and 16 cm in diameter. The principal sign accompanying tumours of cardiac base involved dyspnoea but in 3 cases the tumours yielded no clinical signs. All the diagnoses were additionally verified using immunohistochemical examination. We used antibodies to chromogranin A (clone DAK-A3 1:100), synaptophysin (clone SY38 1:20) and neuron-specific enolase (clone BBS/NC/VI-H14 1:150). An immunohistochemical examination is vital for the diagnosis since it allows to differentiate histologically distinct types of neoplasia which may locate in the same site and may manifest a similar histological pattern.

Possible identification of third stromal component in extraadrenal paraganglioma: myofibroblast in fibrous band and capsule.

Sustentacular and dendritic cells are known as the stromal components of extraadrenal paraganglioma. We identified a third stromal component in such a case. A 66-year-old Japanese woman complained of abdominal pain. The tumor was discovered near the right adrenal gland in the retroperitoneum. Histologically, the tumor consisting of round to oval neoplastic cells with eosinophilic cytoplasm proliferating with a "zellballen" pattern. Sustentacular cells were positive for S-100. Dendritic cells positive for HLA-DR were seen among the neoplastic nests. Additionally, many alpha-smooth muscle actin (ASMA)-positive and hcaldesmon-negative stromal cells, namely, myofibroblasts, were distributed in the capsule and fibrous band. Ultrastructurally, myofibroblasts contained many myofilaments and dense bodies in the cytoplasm. Finally, we identified the third stromal component, namely, myofibroblasts, in the extraadrenal paraganglioma. These myofibroblasts may play a role in the stromal response of host against neoplasm or the regulation of tumor growth.

Extraadrenal paragangliomas. An immunocytochemical and ultrastructural report.

Although the majority of extraadrenal paragangliomas are nonfunctional, some of these tumors are associated with hormone production and clinical symptoms, notably hypertension. The authors have investigated 22 paragangliomas, five of which were diagnosed as clinically functional in a light microscopic immunocytochemical and electron microscopic study (nine cases). Histologically, all the paragangliomas exhibited similar features, with a "Zellballen" pattern of polygonal cells. All 22 cases were strongly immunoreactive to protein gene product 9.5 (PGP 9.5) antisera and moderately reactive to antineuron-specific enolase (NSE) sera. Ten cases (five functional) were focally immunoreactive to antichromogranin sera. Seven cases (four functional) were immunoreactive to neuropeptide Y and enkephalin antisera, and six (five functional) to tyrosine hydroxylase antisera. The clinically functional tumors expressed at least two of the antigens, enkephalin, neuropeptide Y, or tyrosine hydroxylase, whereas none of the 17 nonfunctional possessed more than one of these. Electron microscopic study revealed cells from all the nine cases studied to contain secretory granules. Granule sizes ranged from 100 to 280 nm and the morphologic examination of the secretory granules generally showed a dense core with a membrane-bound halo of variable size. Secretory granules were observed in the five functional cases and these were larger (220-280 nm) than those seen in the nonfunctional tumor cells (100-180 nm). Also, tumor cells from the functional cases contained numerous dilated mitochondrial profiles.