Colorectal paragangliomas with immunohistochemical deficiency of succinate dehydrogenase subunit B.

Recent progress in paraganglioma (PGL) revealed genotype-phenotype relationship, especially succinate dehydrogenase complex subunit B (SDHB) gene mutation-related to the extra-adrenal origin and metastasis. SDHB-immunohistochemistry can detect all types of SDH-subunit mutations, and is a useful tool to detect SDH-mutation tumors. PGLs usually occur along with sympathetic, and parasympathetic chains, however, colorectal paraganglioma is extremely rare. We have experienced one sigmoid colon PGL and one rectal PGL. These colorectal PGLs: a sigmoid colon PGL measuring 25 mm associated with a gastrointestinal stromal tumor (GIST) of the stomach, and a rectal PGL measuring 75 × 45 mm with elevated norepinephrine level were analyzed by immunohistochemistry for INSM1, chromogranin A, synaptophysin, tyrosine hydroxylase, dopamine-beta-hydroxylase, and SDHB and SDHA. The tumors were strongly positive for above markers, however, negative for SDHB. Both PGLs negative for SDHB immunohistochemistry were defined SDHB-deficient PGLs. Histologic grading of the PGLs by GAPP was well differentiated in sigmoid PGL versus poorly differentiated in rectal PGL. Although these PGLs were the same Stage II of TNM classification, the patient with sigmoid colon PGL had neither recurrence nor metastasis for 5 years after the operation, however, the patient with rectal PGL suffered the recurrent multiple metastases and expired 5 years after the operation. Herein, we compared these colorectal PGLs in regard to the patients' prognostic factors. Patient prognosis with these colorectal PGLs was mostly related to the tumor size and histologic grade under the same situation of SDH-deficiency.