hTERT expression in melanocytic lesions: an immunohistochemical study on paraffin-embedded tissue Background: Telomerase plays a role in the immortalization of cells and carcinogenesis. Previous studies have yielded conflicting results on whether human telomerase RNA (hTER) expression differs in nevi, atypical nevi and melanomas using polymerase chain reaction-based telomeric repeat amplification protocol or in situ hybridization assays. The aim of this study was to evaluate human telomerase reverse transcriptase (hTERT) staining in melanocytic lesions on paraffin- embedded tissues. Methods: Paraffin-embedded sections from 12 acquired nevi, seven dysplastic nevi, 11 Spitz nevi, eight primary invasive melanomas, and three metastatic melanomas were studied for staining intensity (0–3þ) and percentage of labeled cells with anti-hTERT. Results: hTERT staining was observed in most cells (>75%), in all but three lesions, and was of greater intensity in the nucleus, especially the nucleolus, compared with the cytoplasm. Spitz nevi tended to have weaker hTERT staining (mean ¼ 1.7) compared with acquired nevi (mean ¼ 2.2), dysplastic nevi (mean ¼ 2.4), primary melanomas (mean ¼ 2.4), or metastatic melanomas (mean ¼ 3). Conclusions: Although telomerase activity was weaker in Spitz nevi, there was overlap with other nevi and primary invasive melanomas in our small series. Thus, hTERT expression does not appear to be a reliable adjunct to the histological diagnosis of primary melanocytic lesions. Fullen DR, Zhu W, Thomas D, Su LD. hTERT expression in mela- nocytic lesions: an immunohistochemical study on paraffin-embedded tissue. J Cutan Pathol 2005: 32: 680–684. # Blackwell Munksgaard, 2005. Douglas R. Fullen 1,2 , Weijian Zhu 1 , Dafydd Thomas 1,3 and Lyndon D. Su 1,2 1 Department of Pathology, 2 Department of Dermatology, and 3 Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, MI, USA Douglas R. Fullen, MD, M3261, Medical Sciences I, Department of Pathology, University of Michigan Medical Center, 1301 Catherine, Ann Arbor, MI 48109-0602, USA Tel: þ1 734 764 4460 Fax: þ1 734 764 4960 e-mail: dfullen@umich.edu Accepted for Publication March 14, 2005 Telomeres are composed of tandem nucleotide repeats (TTAGGG)n and are located on the termini of chromosomes in all vertebrates. The role of telo- meres is to protect chromosomes from degradation and aberrant recombination during replication. 1–5 Telomerase is a ribonucleoprotein DNA polymerase that is responsible for maintaining the length of telomeres on the end of chromosomes. 6,7 This enzyme is repressed in human somatic cells, with a few exceptions, resulting in progressive loss of telomeres and shortening of the chromosome with successive cell divisions. Eventually, chromosomes reach a critical length at which cell division ceases, senescence begins, and the cell ultimately undergoes apoptosis or cell death. 8,9 In contrast, telomerase activity is detectable in germline cells, somatic cells during fetal development, germinal centers of lymph nodes, regenerative epithelium of the gastrointest- inal tract, proliferative endometrium, the bulge region of hair follicles, and stem cells of the epider- mis. 10–15 Immortalized cell lines of a vast array of human cancers, such as breast, colorectal and ovarian can- cer, and melanoma, for example, have been shown J Cutan Pathol 2005: 32: 680–684 Copyright # Blackwell Munksgaard 2005 Blackwell Munksgaard. Printed in Singapore Journal of Cutaneous Pathology 680