Review ArticlesThe Morphologic and Molecular Characteristics of Pilocytic Astrocytomas and the Role of MAPK Pathway What Does Not Kill You Makes You StrongerAktas, Ozge N. MSc; Tihan, Tarik MD, PhDAuthor Information Department of Pathology, Division of Neuropathology, University of California, San Francisco, San Francisco, CA The authors have no NIH funding or conflicts of interest to disclose. Reprints: Tarik Tihan, MD, PhD, Department of Pathology, Division of Neuropathology, University of California, San Francisco, San Francisco, CA 94132-0102 (e-mail: [email protected]).All figures can be viewed online in color at http://www.anatomicpathology.com. Advances In Anatomic Pathology: March 2014 - Volume 21 - Issue 2 - p 144-150 doi: 10.1097/PAP.0000000000000007 Buy Metrics Abstract In recent years, substantial progress has been made in the pathologic and molecular aspects of pilocytic astrocytomas. The advances in the pathologic characterization identified a variant that is currently considered WHO grade II, whereas the classic pilocytic astrocytoma is a WHO grade I neoplasm. Recognition of additional and rare histologic patterns also allowed us to better recognize some tumors that will do “well” in the long run. From a molecular pathologic perspective, recognition of the importance of MAPK pathways in these tumors allowed us to better understand tumors with spontaneous regression or dormant behavior, and tumors that become aggressive, especially those after radiation treatment. As the nature of this highly complex pathway is uncovered, we hope that the findings will allow us to better help the patients with this “chronic” disease. © 2014 by Lippincott Williams & Wilkins.