Topic summaries related to a selection of text in an electronic document may be generated and presented. A topic summary application receives the user-selected text and identifies entities in the text using natural language processing. Using natural language processing, the summary application also identifies related entities and associated text phrases in a remaining portion of the electronic document. The remaining portion may be a portion of the document that precedes the user-selected text, so that a summary generated therefrom may be used to refresh the memory of the user while not revealing information that the user has not yet encountered. In addition, the summary application determines semantically important text phrases using text analytics and generates a summary, presented to the user in a pop-up window, of most frequently correlated related entities along with text phrases that are semantically important.