[Surgical management of a retrorectal tumor with consideration of a rare differential diagnosis].

We present a case of a retrorectal space occupying lesion diagnosed as an adenocarcinoma of unknown primary origin by preoperative histopathology. Localization slightly above the anal sphincter would have required extirpation of the rectum. Rectal palpation, endosonography and radiological imaging, however, suggested a retrorectal tumor or a metastasis of an adenocarcinoma. Both entities would have required local resection. We applied a surgical algorithm including frozen biopsy allowing a stepwise choice of operative procedure from the spectrum in question. The operation performed was thus tailored to the entity of the tumor.