Answer: E. Paraganglioma

Sections show an epithelioid neoplasm arranged in discrete small nests abutting the aorta. The cells are eosinophilic with speckled chromatin and there are numerous large multinucleated hyperchromatic cells. The morphology is the typical “zellballen” appearance of a paraganglioma, the term used for tumors arising from extra-adrenal autonomic tissue. This diagnosis is critical not to overlook because tumors often produce catecholamines leading to dangerous episodes of hypertension which may be exacerbated by surgical manipulation of the tumor. This entity has a very high correlation with germline genetic syndromes and genetic counseling is recommended for all patients. Screening for a subset of syndromes can be achieved with immunohistochemistry for SDH-B, which should be lost if the tumor has mutations in any of the subunits of the SDH complex. Abnormal SDH immunostaining should be confirmed with germline genetic testing but patients invariable harbor germline mutations in one of the SDH subunits. Adrenal cortical carcinoma typically lacks this nested appearance, but there can be morphologic overlap. This tumor occurred outside the adrenal, but a panel of SF1, GATA3, and chromogranin should reliably distinguish pheochromocytoma/paraganglioma from adrenal cortical lesions should the need arise. Both entities typically lack keratin expression and are frequently synaptophysin positive so these stains are not useful in their distinction. Olfactory neuroblastoma shares a nested and lobulated architecture with paraganglioma and has a very similar immunoprofile – both express neuroendocrine markers and lack keratin expression, but the former entity is restricted to the area around the cribriform plate. Alveolar soft part sarcoma is an epithelioid, eosinophilic tumor but has the cytologic monotony associated with translocation tumors, lack expression of neuroendocrine markers and GATA3 and would harbor TFE3 rearrangement.