Searching for an intrinsic neuroendocrine cell in the kidney - An immunohistochemical study of the fetal, infantile and adult kidney

The pathogenesis of primary renal carcinoid tumor is unknown. One hypothesi s has implied derivation from a yet unrecognized intrinsic neuroendocrine c ell in the renal parenchyma/hilum either as a minute endocrine-paracrine co nstituent or resulting from entrapped/misplaced progenitor cells of the so- called dispersed neuroendocrine system during organogenesis, Immunohistoche mical staining for chromogranin and serotonin was systematically performed on a whole-mount and geographically mapped normal adult kidney, kidneys fro m 15 fetuses (age range: 15 to 38 weeks), and renal specimens from 18 infan ts/children (age range: 7 days to 123 months). Minute paraganglion nests (c omposed of chromogranin positive/serotonin negative chief cells and S-100 p rotein positive dendritic cells) were incidentally detected within the rena l hilum primitive stroma (unilaterally) of two fetuses at 22 and 26 weeks. Sequestration and persistence of such paraganglion nests during renal growt h and maturation would offer a basis for the rare occurrence of extra-adren al paraganglioma involving the renal hilum/pedicle. Otherwise, no neuroendo crine cell was detected within the renal parenchyma or hilum, therefore not validating/sustaining the aforementioned hypothesis in the pathogenesis of renal carcinoid tumor.