Ikram Asad, Rehman Anis
University of New Mexico
District Endocrine/Sentara Northern Virginia Medical Center
Paraganglia are groups of neural crest-derived neuroendocrine cells classified as adrenal or extra-adrenal. Paragangliomas, rare and highly vascular tumors, originate from sympathetic or parasympathetic extra-adrenal autonomic paraganglia. Some refer to them as extra-adrenal pheochromocytomas, while others might designate a pheochromocytoma as an intra-adrenal paraganglioma. About 86% of paragangliomas located outside of the head and neck are sympathetic, secreting norepinephrine, unlike the more differentiated intraabdominal adrenal medulla tumors neuroblastoma and pheochromocytoma which primarily secrete epinephrine. Associated symptoms are episodic hypertension, tachycardia, headache, and diaphoresis. Sympathetic paragangliomas arise anywhere along the sympathetic chain, from the skull base to the bladder and prostate. Most commonly, they occur at the vena cava and the left renal vein junction or the aortic bifurcation near the take-off of the inferior mesenteric artery known as the organ of Zuckerkandl. Tumors originating from parasympathetic origin are usually asymptomatic and inactive, predominantly located in the neck and skull base along the distribution of the vagus and glossopharyngeal nerves. Most parasympathetic paragangliomas arise from the carotid body (see Carotid Artery Tumor), but some originate from the jugulotympanic and vagal paraganglia. Rarely one originates from the laryngeal paraganglia. Only about 5% of tumors in the neck and skull base secrete catecholamines. Jugulotympanic paragangliomas and carotid body paragangliomas comprise approximately 80% of the paragangliomas in the head and neck. Paragangliomas commonly present as a single, benign, unilateral tumor, but 1% of sporadic and 20% to 80% of familial cases may have multiple tumors. Instances of malignancy and metastasis are rare. Early identification leading to complete surgical resection is often curative and carries a favorable prognosis. Detecting distant metastases is the only reliable way to assess the biological aggressiveness of paragangliomas. Paragangliomas are primarily sporadic, although 30% to 50% of cases are familial. Some familial forms may be associated with genetic syndromes, such as variations in the genes encoding different subunits of the succinate dehydrogenase (SDH) enzyme, Carney-Stratakis dyad, neurofibromatosis type 1 (NF1), von Hippel-Lindau (VHL), and multiple endocrine neoplasia types 2A and 2B (MEN2). A surgical biopsy performed during resection is the gold standard for confirming the diagnosis. However, it does not distinguish between pheochromocytomas and paragangliomas. Typically, clinical correlation suffices for diagnosis, aided by imaging and pathological findings of the lesion.
副神经节是神经嵴衍生的神经内分泌细胞群，分为肾上腺性或肾上腺外性。副神经节瘤是罕见的高血管性肿瘤，起源于交感或副交感肾上腺外自主神经节。有些人将其称为肾上腺外嗜铬细胞瘤，而另一些人可能将嗜铬细胞瘤指定为肾上腺内副神经节瘤。位于头颈部以外的副神经节瘤约86%是交感神经的，分泌去甲肾上腺素，这与分化程度更高的腹内肾上腺髓质肿瘤神经母细胞瘤和嗜铬细胞瘤不同，后者主要分泌肾上腺素。相关症状为发作性高血压、心动过速、头痛和多汗。交感神经副神经节瘤可出现在交感神经链的任何部位，从颅底到膀胱和前列腺。最常见的是，它们发生在腔静脉和左肾静脉交界处或肠系膜下动脉起始处附近的主动脉分叉处，即所谓的祖克坎德尔器。起源于副交感神经的肿瘤通常无症状且不活跃，主要位于颈部和颅底，沿迷走神经和舌咽神经分布。大多数副交感神经副神经节瘤起源于颈动脉体（见颈动脉肿瘤），但有些起源于颈静脉鼓室和迷走神经节。很少有起源于喉神经节的。颈部和颅底的肿瘤中只有约5%分泌儿茶酚胺。颈静脉鼓室副神经节瘤和颈动脉体副神经节瘤约占头颈部副神经节瘤的80%。副神经节瘤通常表现为单个、良性、单侧肿瘤，但1%的散发性病例和20%至80%的家族性病例可能有多个肿瘤。恶性和转移情况罕见。早期识别并导致完整手术切除通常可治愈且预后良好。检测远处转移是评估副神经节瘤生物学侵袭性的唯一可靠方法。副神经节瘤主要是散发性的，尽管30%至50%的病例是家族性的。一些家族性形式可能与遗传综合征有关，如编码琥珀酸脱氢酶（SDH）不同亚基的基因变异、卡尼 - 斯特拉塔基斯二联征、1型神经纤维瘤病（NF1）、冯·希佩尔 - 林道病（VHL）以及2A和2B型多发性内分泌腺瘤病（MEN2）。切除术中进行的手术活检是确诊的金标准。然而，它无法区分嗜铬细胞瘤和副神经节瘤。通常，临床相关性结合病变的影像学和病理学发现足以进行诊断。
