Case 4 -

Paraganglioma Ricardo V. Lloyd and Arie Perry

Clinical History A 37-year-old woman had a retroperitoneal mass and mild hypertension. The mass was excised and reported to be keratin and chromogranin negative. The tumor was large (10 x 8 x 6 cm) and was located in the region of the bifurcation of the aorta. Cut section was hemorrhagic with some firm, tan areas. Case 4 - Figure 1 Case 4 - Figure 2 Case 4 - Figure 3 Microscopic Description The tumor grew in sheets with focal areas showing cell nests. Mitotic activity was moderate, and there were focal areas of necrosis. Repeat stains for keratin were negative, but synaptophysin and a repeat chromogranin were positive. S100 protein was negative. In situ hybridization for chromogranin A + B mRNA was positive with variable cytoplasmic staining. Discussion Paragangliomas are part of the diffuse or dispersed neuroendocrine system (DNES). They can be divided into two groups—paraganglia in the head and neck region including the aorticopulmonary paraganglia which have a close alignment with the parasympathetic nervous system and the paraganglia of the sympathoadrenal neuroendocrine system. Most paragangliomas are positive for general neuroendocrine markers such as chromogranin and synaptophysin. Although most paragangliomas are negative for keratin, some paragangliomas from along the neuraxis such as the ones from the cauda equina region may be positive. The diagnosis of malignant paraganglioma is difficult to make without metastatic disease [1, 2, 3, 4, 5] . Retroperitoneal paragangliomas such as this case have the highest rate of malignancy (24-50%). Features most frequently associated with malignancy include extra-adrenal location, coarse nodularity of the primary tumor, confluent tumor necrosis, and absence of hyaline globules. Malignant tumors are larger, have a higher mitotic rate, and a higher rate of vascular invasion, but these features were not prognostically significant in one study [4]. Some studies have suggested that malignant paragangliomas are less likely to express S100 protein in sustentacular cells [5]. Immunohistochemical detection of chromogranin A have been very useful in the characterization of neuroendocrine tumors [6, 7, 8, 9, 10] . Since chromogranin A protein is associated with secretory granules, neuroendocrine cells and tumors with few secretory granules may be falsely negative for chromogranin A. Several approaches can overcome this potential pitfall including using other broad spectrum neuroendocrine markers such as synaptophysin [8] and proconvertases [11, 12] using a cocktail of other markers of the chromogranin secretogranin family such as chromogranin A, chromogranin B, and secretogranin II [13, 14, 15, 16, 17, 18] (Table 1) or performing ISH to detect the mRNA for chromogranin A which is not associated with secretory granules Table 1. Chromogranin/Secretogranin Family Designation Molecular Mono (kDa) mRNA Chromosomal Location Proteolytic Products Chromogranin A 49 2.1 14 Pancreastatin Parastatin Chromostatin Chromogranin B 75 2.5 20 GAWK CCB Secretogranin II 68 2.5 --   Secretogranin III (B1075) 57 2.3 9 Secretoneurin Secretogranin IV HISL-19 NA NA NA -- Secretogranin V 7B2 21 1.35 15 -- We recently developed a probe cocktail combining chromogranin A and B oligonucleotides for ISH [10]. The present case was positive for chromogranin A + B mRNAs, in spite of the negative staining for chromogranin A protein. An increasing number of reports have shown a discordance between ISH and immunohistochemical staining in the workup of endocrine neoplasms or neoplasms with endocrine differentiation in a small percentage of cases [19, 20, 21, 22, 23, 24, 25, 26] (Table 2). Table 2. Detection of mRNA by ISH when Proteins are not Detected by Immunohistochemistry Diagnosis Product Reference GH Adenoma GH [19, 20] Neuroendocrine Tumors Chromogranin [16, 17, 18, 26] Medullary Thyroid CA Calcitonin -- Small Cell Lung Carcinoma Bombesin, Chromogranin A [21, 22, 25] Gastrinoma Gastrin, POMC [23] Pheochromocytoma with Cushing's POMC/ACTH -- Breast Carcinoma Estrogen Receptor [24] The most common explanation for a positive ISH and a negative immunohistochemistry result is that the tumor is rapidly secreting but not storing the protein product, while the mRNA is almost always present intracellularly [27]. Other possible explanations include decreased translational processing of the gene product or marked differences between sensitivities of specific antibodies and probes. The detection of estrogen receptor mRNA and protein in breast carcinomas has been discordant in previous studies with a higher percentage of cases expressing the mRNA [24]. However, the clinical significance of these findings in terms of clinical management of patients with breast carcinomas remains uncertain. References Kimura N, Sasano N, Yamada R, Satoh J. Immunohistochemical study of chromogranin in 100 cases of pheochromocytoma, carotid body tumor, medullary thyroid carcinoma, and carcinoid tumour. Virchows Arch A Pathol Anat Histopathol 1988;413:33-38 Johnson TL, Zarbo RJ, Lloyd RV, Crissman JD. Paragangliomas of the head and neck: immunohistochemical, neuroendocrine, and intermediate filament typing. Mod Pathol 1988;1:216-223 Lack EE, Cubilla AL, Woodruff JM, Lieberman PH. Extra-adrenal paragangliomas of the retroperitoneum: a clinicopathologic study of 12 tumors. Am J Surg Pathol 1980;4:109-120 Linnoila RI, Lack EE, Steinberg SM, Keiser HR. Decreased expression of neuropeptides in malignant paragangliomas: an immunohistochemical study. Hum Pathol 1988;19:41-50 Lloyd RV, Blaivas M, Wilson BS. 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