11] Our immunohistochemical analysis revealed that the tumor was positive for Chromogranin A, S-100, cytokeratin negative and Ki67 index <2% with a characteristic zellballen pattern on histopathology, thus providing a basis for a correct diagnosis of nonchromaffin
paraganglioma of the retroperitoneum in the patient arising from pancreas.
Neoplasms of these cells are termed chemodectomas or nonchromaffin
paragangliomas (JOHNSON, 1968; CAPEN, 2002), and are frequently described in the aortic and carotid bodies of domestic animals (CAPEN, 2002).
Lack of malignancy is determined only by the absence of spread of the tumor to nonchromaffin
tissues over time.
Paragangliomas traditionally are divided into chromaffin paragangliomas (associated with the sympathetic nervous system) and nonchromaffin
paragangliomas (associated with the parasympathetic nervous system and derived from structures presumed to function as chemoreceptors).