SCC, originally isolated from cervical cancer tissue, is a serine protease inhibitor and a highly specific tumor marker used primarily for the diagnosis of squamous carcinoma. SCC is distributed within squamous epithelial cells in normal tissues throughout the body, and therefore normal peripheral blood contains a range of SCC levels. However, with the malignant proliferation of squamous epithelial cells, intracellular SCC is rapidly released into the blood, thus triggering an increase in peripheral blood SCC. Therefore, SCC is of interest for the diagnosis and monitoring of all cancers of squamous epithelial cell origin. For example, cervical squamous carcinoma, lung squamous carcinoma, esophageal squamous carcinoma, oral squamous carcinoma, nasopharyngeal carcinoma, bladder carcinoma, anal canal carcinoma, and skin carcinoma. For the above tumors that have been detected, there is a close relationship between the changes in SCC concentration and the efficacy of its treatment, the recurrence, metastasis and progression of the disease, as well as the assessment of prognosis: abnormally elevated clinical SCC levels should be taken seriously and alerted to the occurrence of the above tumors: once abnormally elevated SCC levels occur, firstly, repeated blood sampling is needed for further reexamination to exclude the cause of laboratory errors: if it is still high, it If the SCC level is still high, further comprehensive physical examination and imaging, such as enhanced CT examination of the chest, abdomen and pelvis, are needed. An abnormally high SCC often indicates the presence of a lesion, which can be detected at the earliest by PET-CT. Early detection and early treatment will result in better outcomes. Clinically, SCC may appear months before the signs and symptoms, so even if no abnormalities are found on imaging, it is important to monitor the changes of SCC with close follow-up: SCC only indicates the risk of squamous carcinoma in the body, and further confirmation of the diagnosis is needed, which requires imaging and pathology. SCC has the same clinical importance in monitoring tumor recurrence.