Diagnostic value of ascites immunohistochemistry in carcinomatosis of unknown origin

We present the case of a patient diagnosed with carcinomatosis when admitted urgently for an occlusive condition. It is the immunohistochemistry that clarifies which is the primary tumor. Sigma neoplasia was initially suspected to recur due to operative findings. It was surprising that the primary tumor was of pulmonary origin. It became known thanks to the immunohistochemical cytology of the ascetic fluid.