Pathohistologic findings in liver metastases

Metastatic tumors are the most common malignancies of the liver. The frequency distribution of the primary tumor location site closely resembles the frequency distribution of primary cancers in general. Yet, due to the liver's filter function of the portal bloodstream, metastatic tumors of the gastrointestinal tract are overrepresented. Most metastatic tumors show a nodular growth pattern with a demarcation of the tumor by inflammatory or fibrous reactive tissue; a diffuse metastatic tu mor spread within the sinusoids is uncommon. Metastatic liver tumors may be the first clinically detectable manifestation of an unknown primary tumor. In these cases, the histological and immunohistochemical pattern of the metastatic tumor cells may give a clue of the location of the corresponding primary tumor.