Rossi F, Gonzalez C. Studying tumor growth in Drosophila using the tissue allograft method. Nat Protoc. 2015 Oct;10(10):1525-34. PMID: 26357008.
From the abstract: "This protocol describes a method to allograft Drosophila larval tissue into adult fly hosts that can be used to assay the tumorigenic potential of mutant tissues. The tissue
of interest is dissected, loaded into a fine glass needle and implanted
into a host. Upon implantation, nontransformed tissues do not overgrow
beyond their normal size, but malignant tumors grow without limit, are
invasive and kill the host. ... This method also provides an operational definition of hyperplastic, benign and malignant growth. ..."
See also a post at The Node on this 80-year-old technique: