Prognostic markers play an important role in our understanding of
tumors and how to treat them.
Thymidine kinase 1 (TK1), a proliferation marker involved in DNA repair, has been shown to have independent prognostic potential. This prognostic potential includes the novel concept that upregulation of serum TK1 levels is an early event in
cancer development. This same effect may also be seen in
tumor tissue. In order to demonstrate that TK1 upregulation is an early event in
tumor tissue formation, tissue arrays were obtained and stained for TK1 by immunohistochemistry. Using a progressive breast tissue array, precancerous tissue including
breast adenosis, simple
hyperplasia, and atypical
hyperplasia stained positive for TK1 expression. Different stages of
breast carcinoma tissue also stained positive for TK1 including nonspecific infiltrating duct, infiltrating lobular, and infiltrating duct with
lymph node metastasis carcinomas. This indicates that TK1 upregulation is an early event in
breast carcinoma development, and may be useful in identifying precancerous tissue. Further work is needed to better understand the differences seen between TK1 positive and negative tissues.