Serum thymidine kinase 1 is a reliable maker for the assessment of the risk of developing malignancy: A case report

With regard to different types of malignancies, thymidine kinase 1 (TK1) is a useful prognostic marker in clinical oncology, both as a serum proliferation marker and in immunohistochemistry. The present study investigated the use of serum TK1 protein (STK1p) for the identification of multiple proliferating diseases linked to the risk of developing cancer, by following one patient during the period of 2003-2014. The patient presented with adenomatous polyps in the stomach in 2003, follicular cervicitis in 2007 and hyperplasia of the breast/fibrocystic breasts in 2010. The breast cysts increased from 4×5 mm in size in 2010 to 8×7 mm in size in 2013, and were assessed as a suspicious malignancy at the end of this period. In parallel, the STK1p values increased from 2.0 to 7.6 pM. Based on this information, a minimally invasive surgery using the Mammotome® Biopsy System was performed. Immunohistochemistry on the cyst tissue showed strong staining of TK1 in the ductal epithelial cells and thus confirmed the abnormal proliferation in the lesion. One week after the surgery, the STK1p value had decreased to almost normal values (1.6 pM), but then fluctuated above 2.0 pM for the next 7 months. After the surgery, the patient was re-examined and small foci with squamous cell hyperplasia and a suspected ulcerated cervix, as well as flat gastric erosive, were identified, but not treated; this may explain why the STK1 P-values did not return to within normal values. The patient is currently being followed up using STK1p analysis combined with imaging/pathology in order to begin therapeutic intervention as early as possible to avoid the risk of developing cancer. Overall, STK1p is useful in health screening to identify individuals at risk of developing premalignancy/malignancy.