[Cutaneous apudoma. Apropos of a case and review of the literature].

It has been suggested that Merkel Ranvier cells, generally considered as belonging to the Apud system, may be the origin of extremely rare skin tumors. The authors analyse the characteristics of an apudoma in connexion with a case, and compare their findings with those of 58 other cases reported in the literature. With light microscopy techniques, the differential diagnosis is essentially one of a non-differentiated primary or secondary carcinoma, or of a lymphosarcoma. Detection by electron microscopy of neurosecretory granules in the cell cytoplasm, the neuron-specific enolase activity, when this is detectable, the possibility of ectopic polypeptide secretions, and the evolution potential of the tumor, are all features warranting inclusion of this type of tumor in the category of apudomas.