Pseudogliomatous growth pattern of anaplastic small cell carcinomas metastatic to the brain

Carcinomas metastatic to the brain usually grow very well circumscribed, wi th sharp delineation. Radiosurgery takes advantage of this fact by using th e gamma knife for definitive treatment of small metastases. We report a sys tematic study of the growth pattern of cerebral metastases, focusing on tum or delineation. In 26 cases of 66 metastatic anaplastic small cell carcinom as and in one case of adenocarcinoma, we observed poorly defined borders an d a highly diffuse pattern of invasion. Infiltrating carcinoma cells change d to an elongated shape adapting to preexisting tissue structures. This pse udogliomatous growth pattern of some brain metastases - apparently most lik ely in neuroendocrine carcinomas - is of potential importance for therapeut ic strategies in the treatment of brain metastases, especially when conside ring treatment with radio-surgery and gamma knife.