GH1 and neoplasm: 6a). The proliferation index was very low with approximately 3% of cells showing immunoreactivity against MiB-1 (fig. 6b). Parts of the tumour cells showed immunopositivity for prolactin in peripheral parts of cytoplasm (fig. 6c). However, no immunoreactivity was present that provided an antibody against the human growth hormone (fig. 6d).