[Anorectal anaplastic cancer (neuroendocrine)].

An extensive case of undifferentiated neuroendocrine carcinoma with small cells of the anorectal region is reported. The carcinoma is related to pulmonary anaplasia and quite rare in the colonic and rectal region. Its aggressivity is considerable with a strong propensity for hematogenous and lymphatic metastases and with a disastrous prognosis: 0% survival over 1 year. The incidence, the characteristic features, the histogenesis, and the anatomical pathology of this rare neoplasm are mentioned. Furthermore, the case illustrates a radiological pattern typical for major lymphatic dissemination with an intra- and extraparietal component. The mechanism of dissemination is explained by the "lymphatic block" theory. The absolute necessity of obtaining an histology in radiologically unusual and/or extensive cases is mentioned.