The anatomical distribution and morphology of extraadrenal chromaffin tissue (abdominal paraganglia) in the dog

Imaging features of retroperitoneal extra-adrenal paragangliomas in 10 dogs

Retroperitoneal paragangliomas are rare tumors of the neuroendocrine system. Only a few canine case reports are available with rare descriptions of their imaging features. The objectives of this multi‐center, retrospective case series study were to describe the diagnostic imaging features of confirmed retroperitoneal paragangliomas and specify their location. Medical records and imaging studies of 10 affected dogs with cytological or histopathologic results concordant with retroperitoneal paragangliomas were evaluated. Dogs had a median age of 9 years. Four of them had clinical signs and laboratory reports compatible with excessive production of catecholamines. Six ultrasound, four CT, four radiographic, and one MRI studies were included. The paragangliomas did not have a specific location along the aorta. They were of various sizes (median 33 mm, range: 9–85 mm of length). Masses had heterogeneous parenchyma in six of 10 dogs, regardless of the imaging modality. Strong contrast enhancement was found in all CT studies. Encircling of at least one vessel was detected in six of 10 masses, clear invasion of a vessel was identified in one of 10 masses. In five of 10 cases, the masses were initially misconstrued as lymph nodes by the on‐site radiologist. Retroperitoneal paragangliomas appear along the abdominal aorta, often presenting heterogeneous parenchyma, possibly affecting the local vasculature, and displaying strong contrast enhancement on CT. Clinical signs can be secondary to mass effects or excessive catecholamine production. Underdiagnosis and misdiagnosis of this tumor are suspected as they can be silent, of small size, or confused with other structures.

Subcutaneous ureteral bypass for treatment of bilateral ureteral obstruction in a cat with retroperitoneal paraganglioma

CASE DESCRIPTION A 7-year-old female domestic shorthair cat was referred for evaluation of azotemia and unilateral hydronephrosis. CLINICAL FINDINGS Abdominal ultrasonography revealed right-sided hydronephrosis and dilation of the proximal aspect of the ureter; the left kidney was small with irregular margins. A highly vascular, irregular retroperitoneal mass, not clearly associated with the ureteral obstruction, was also visualized. Surgical exploration confirmed a retroperitoneal mass involving the caudal mesenteric artery and both ureters, with hydroureter on the right side. TREATMENT AND OUTCOME A subcutaneous ureteral bypass (SUB) device was surgically implanted to treat right ureteral obstruction, and the mass was biopsied. Shortly after surgery, progressive azotemia and hyperkalemia were detected; ultrasonographic examination revealed left-sided hydronephrosis and hydroureter, which was suspected secondary to inflammation of the mass causing a left-sided ureteral obstruction. A second surgery was performed to place an SUB device for the left kidney and remove the retroperitoneal mass; both ureters were ligated at the mid- and distal aspects and then transected and removed with the mass. A neuroendocrine paraganglioma was identified by histopathologic evaluation of the mass. Hydronephrosis improved (right kidney) or resolved (left kidney) after surgery, and azotemia improved. Chemotherapeutic intervention was declined. Markers of renal function were static during the 14-month follow-up period. At the last follow-up evaluation, the patient was reportedly doing well, and both SUB devices were patent. CLINICAL RELEVANCE This was the first report of retroperitoneal paraganglioma in a domestic cat causing bilateral ureteral obstruction. Bilateral SUB device placement enabled en bloc mass resection and provided long-term relief of ureteral obstruction.

From proliferation to target innervation: signaling molecules that direct sympathetic nervous system development

The sympathetic division of the autonomic nervous system includes a variety of cells including neurons, endocrine cells and glial cells. A recent study (Furlan et al. 2017) has revised thinking about the developmental origin of these cells. It now appears that sympathetic neurons and chromaffin cells of the adrenal medulla do not have an immediate common ancestor in the form a "sympathoadrenal cell", as has been long believed. Instead, chromaffin cells arise from Schwann cell precursors. This review integrates the new findings with the expanding body of knowledge on the signalling pathways and transcription factors that regulate the origin of cells of the sympathetic division of the autonomic nervous system.

Extra-adrenal retroperitoneal paraganglioma in a dog

An extra-adrenal retroperitoneal paraganglioma was observed in a 10.5-year-old male Boxer dog. Additionally, the dog had an aortic base tumor, multiple thyroid adenomas, multiple testicular interstitial cell tumors, bilateral nodular adrenal cortical hyperplasia, and parathyroid gland hyperplasia. The hypothesis that the retroperitoneal mass represents a primary extra-adrenal paraganglioma rather than metastatic mass from the aortic body tumor is considered. Either primary or metastatic extra-adrenal retroperitoneal paragangliomas are rarely reported in dogs.

Morphological observations of small granule-containing (chromaffin) cells in the celiac ganglion of the guinea pig, with emphasis on cell contacts

Utilizing electron microscopic observation, several contacts between small, granule-containing cells (SGC) and postganglionic neurons (PGN) in the celiac ganglion of the guinea pig have been observed. A SGC in very close association with a PGN was seen to receive a distinct synaptic contact that contained many vesicles with dense cores. This contact was morphologically unlike cholinergic synapses previously reported on chromaffin cells. Because the SGC and PGN were clearly separated by a thin rim of satellite cell cytoplasm mutual to both cells, it is not known how or if the SGC would possibly exert a synaptic or paracrine effect on the PGN. Also, intraganglion SGC existed as large well-vascularized islands within the celiac ganglion. These intraganglion clusters sometimes contained more than 50 cells and perhaps could be considered to function as localized neuroendocrine components within the ganglion by secreting granule products into the nearby blood vessels for local or distant effects, although this certainly is not known. This work reports a unique synaptic ending upon a single-occurring SGC, which, in turn, closely approximates a ganglion neuron in a soma-somatic relationship. In addition, a very close association (but no actual contact) was observed between granule-containing processes, presumably emanating from the intraganglion clusters, and PGN. Whatever the function of ganglionic SGC may be, the exact relationship between SGC and PGN presumably would be of great interest and potential importance.

Mitotic cell division in the extraadrenal chromaffin system of various species

Mitotic activity often has been reported in embryonic and fetal sympathetic neuroblasts, principal sympathoblasts, and primitive sympathetic cells in various species at different stages of development. Postnatal adrenal medullary cells also are known to undergo mitosis, but such dividing capabilities rarely have been observed in the true postnatal extraadrenal chromaffin system. Although few in number, this work nevertheless has clearly identified such cells in varying stages of the mitotic cycle in the young dog, Syrian hamster, mouse, rabbit, and rat. The dividing cells were noted in paraaortic chromaffin organs, paraganglia, and within the inferior mesenteric ganglion as well. They displayed the morphological character usually associated with their adrenal medullary catecholaminergic counterparts, including numerous dense-cored vesicles known to be the harbingers of catecholamines and various peptides. Nerve endings were not noticed upon the mitotic cells. The phenomenon of dividing extraadrenal chromaffin cells augments existing data and perhaps suggests that these cells are more endocrine than neural in type and subservient to the adrenal medulla in its classic endocrine function.

Pre- and postnatal development of rat retroperitoneal paraganglia

The prenatal and postnatal development of the rat retroperitoneal paraganglia were studied using the formaldehyde-induced catecholamine fluorescence (FIF) method. In addition, the transmitter composition of the paraganglionic cells of the newborn rat was analyzed by immunohistochemical demonstration of the catecholamine-synthesizing enzymes. The first fluorescent preaortic cells were detected in the 13.5-day-old embryos. One day later these cells constituted a distinct organ with moderately fluorescent cells, and in 15.5-day-old embryos this organ consisted cranially of moderately fluorescent and caudally of brightly fluorescent cells. The organ reached its largest size at birth and afterwards fibrous material increased between the fluorescent cells. In 4-week-old animals, only small clusters of fluorescent cells were observed in the preaortic area although many small paraganglia were situated cranially near the coeliac ganglion. In the organ of the newborn rat, many cells showed bright FIF. In addition, some cells with only slight or moderate fluorescence as well as non-fluorescent cells were detected. The analysis of immunoreactivity to the catecholamine-synthesizing enzymes showed that there was a cell population with intense reactivity to both tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH). These cells were considered as paraganglion-type cells. Some of them were also immunoreactive to phenylethanolamine N-methyltransferase (PNMT). In addition, there were cells with weak to moderate reactivity to TH and DBH but not to PNMT. Also totally negative cells were constantly seen. These findings were confirmed by using consecutive sections for the localization of different enzymes and by using the Tramu method to elute previous staining and by restaining the same sections with the other antibodies. It is concluded that the retroperitoneal paraganglia of newborn rat consist of many paraganglion-type cells containing noradrenaline, some of them containing also adrenaline, a few neuron-like cells with TH and DBH immunoreactivity, and cells containing no catecholamines.

Location and size of carotid body-like organs (paraganglia) revealed in rats by the permeability of blood vessels to Evans blue dye

We determined the number, distribution size, and morphology of paraganglia near the glossopharyngeal, vagus, and sympathetic nerves of rats. The location of paraganglia was revealed by a method that takes advantage of the comparatively high permeability of their blood vessels to Evans blue dye. Rats were fixed by vascular perfusion of glutaraldehyde 2 min after receiving an intravenous injection of Evans blue dye. Paraganglia appeared as circumscribed, intensely blue structures that were readily distinguished from unstained nerves associated with them. Similarly, some groups of small intensely fluorescent (SIF) cells in autonomic and sensory ganglia were surrounded by Evans blue at a time that other portions of the ganglia contained little detectable dye. An average of 92.5 (range 41-134) paraganglia and 41 (range 17-68) blue spots in ganglia were found in the neck, thorax and abdomen of each of 10 rats. Carotid bodies had a mean length of 601 +/- 123 micrometer, width of 275 +/- 65 micrometer, and volume of 25.1 +/- 11.2 micrometer 3 X 10(6). Other paraganglia had an average length of 168 +/- 108 micrometer, width of 77 +/- 41 micrometer, and volume of 0.87 +/- 1.55 micrometer 3 X 10(6). The total volume of paraganglion tissue averaged 128 micrometer 3 X 10(6) (range 62-215 micrometer 3 X 10(6)), 59% of which was due to paraganglia other than the carotid bodies. By using fluorescence microscopy, we verified that small catecholamine-containing cells, visible because of their yellow-green fluorescence induced by formaldehyde gas, were located in regions along nerves and within ganglia that contained extravascular dye, visible because of its red fluorescence. Electron-microscopic studies confirmed that blue-stained organs (presumptive paraganglia) associated with the superior laryngeal nerve and other branches of the vagus nerve contained cells morphologically similar to glomus cells of the carotid body. Celiac ganglia contained, in addition, some cells similar to chromaffin cells of the adrenal medulla. Paraganglia (but not in SIF cells in ganglia) were encapsulated by layers of perineurium, which may constitute a barrier to diffusion. Tortuous thin-walled blood vessels, some with a fenestrated endothelium, were present in all paraganglia examined and were near most groups of SIF cells in ganglia. Neural connections of the small catecholamine-containing cells varied. Most nerve terminals on cells in paraganglia resembled sensory nerve endings on glomus cells of the carotid body, although some were morphologically similar to preganglionic nerves on chromaffin cells of the adrenal medulla.