Functional cardiac paraganglioma associated with a rare SDHC mutation.

Paragangliomas are catecholamine-secreting tumors external to the adrenal glands, most commonly arising in the head and neck, followed by the abdominal and thoracic cavities. The heart is a rare location for paragangliomas to originate from, with fewer than 50 cases as described in the literature. Functional paragangliomas of the right atrium are even more unusual, with only five cases reported to date. The investigations and therapies of a 41-year-old male presenting with a clinically functional cardiac paraganglioma are discussed. We performed a detailed pathology review of the primary cardiac tumor and a lung nodule to examine morphologic changes, along with an immunohistochemical profile (chromogranin A, tyrosine hydroxylase, MIB-1, and succinate dehydrogenase subunit B (SDHB)) of both tumors. Genetic testing of germline mutations in SDH genes was also completed. Both the 9.5-cm cardiac mass and 0.5-cm lung nodule were positive for chromogranin A and tyrosine hydroxylase and showed a global loss of SDHB expression. The MIB-1 labeling index of the smaller lesion and the bulk of the larger lesion was <5 %, but there were cellular foci of the larger lesion that had a labeling index of 10%. Genetic testing yielded an intronic frameshift mutation in the SDHC gene, c.IVS 5 + 1, G > A. We report the first case of a functional cardiac paraganglioma associated with an intronic frameshift SDHC gene mutation.