IMMUNOCYTOCHEMICAL IDENTIFICATION OF OXYPHILIC MITOCHONDRION-RICH CELLS

Mitochondrion-rich oxyphilic cells and related tumors are recognizable morphologically. However, oxyphilic properties are unspecific because , in some instances, they are related to intra-cytoplasmic accumulatio n of organelles other than mitochondria, and the cytological typing do es not correspond to the ultrastructural one. Moreover, the extent of oxyphilic transformation in some cases might not be so prominent, and the typical features of large granular eosinophilic cytoplasm might be missing. This is true especially in poorly differentiated oxyphilic t umors, as observed in some Hurthle cell carcinomas and in composite tu mors in which the oxyphilic cell population is admired with other cell types (e.g., kidney and thyroid carcinomas). A commercially available monoclonal antibody (clone 113-1), which recognizes a mitochondrial a ntigen, was evaluated by immunohistochemistry in formalin-fixed, paraf fin-embedded tissues with an oxyphilic cell component and in a series of oncocytic tumors. A working dilution of 1:100 was chosen for immuno peroxidase staining: this allowed marking of selectively mitochondrion -rich cells and tumors but not normal tissues, non-oxyphilic carcinoma s, or tumors with oxyphilic properties unrelated to mitochondria. In s ome tumors, especially in thyroid and kidney neoplasms, oxyphilic appe arance has been linked to a unique biological behavior. The marker her e tested can be useful to reach more definite and reproducible criteri a for the definition of mitochondrion-rich oxyphilic cells.