How to count and measure features on slides

This review describes how to count and measure features of interest to diagnostic pathologists on microscopic slides. The description of counting focuses on mitotic counts in tumour pathology but also describes some other forms of counting, such as Johnsen counts in testicular biopsies, Ki67 proliferation index, oestrogen receptor counts and fluorescent in situ hybridization (FISH) counting. The description of measurement focuses on linear measurement, particularly the use of the Breslow system in cutaneous melanoma. The final sections describe two specialized uses of histomorphometry in skeletal muscle biopsies and in metabolic bone biopsies.