The maximum number of series that the download manager can manage from a single shopping cart is somewhere around 3500. The limit is imposed by Java. To determine how many series are in your basket at a given time, on the left nav at the top (under My Data Basket > View Contents) the number of series in a basket will display.
Questions about the TCGA-related imaging data:
How do I find out additional information about brain tumors?
Please refer to the TCGA-GBM collection as a well-documented collection of of brain-tumor images as described in: https://wiki.cancerimagingarchive.net/display/Public/TCGA-GBM
(This wiki page also links to the wiki pages describing the related research activities and related resources). On this page, in the Related Data section, there is a link to a blank GBM Case Quality Control Form that details the kinds and decriptions of clinical data collected. The data are freely available from the TCGA Data Portal: https://tcga-data.nci.nih.gov/tcga
Once here, the you would click on the link to the Glioblastoma multiforme [GBM] data. Since TCIA does not host the TCGA Data Portal, we do not offer guidance for browsing the Data Portal.