Any cellular protein catabolic process that takes place in a lysosome. [ GOC:PARL GOC:bf GOC:TermGenie http://purl.obolibrary.org/obo/go/references/0000062 http://www.ncbi.nlm.nih.gov/pubmed/24334770 ]
Synonyms: cellular protein breakdown in lysosome cellular protein catabolic process in lysosome lysosomal protein degradation lysosomal protein catabolism cellular protein degradation in lysosome cellular protein catabolism in lysosome