Squamous cell carcinoma in situ

by Jason Wasserman MD PhD FRCPC
December 17, 2023

Squamous cell carcinoma in situ

Squamous cell carcinoma in situ is a non-invasive type of cancer made up of squamous cells. It is called non-invasive because the abnormal cells have not spread into any of the surrounding tissues. If left untreated, this condition can turn into a type of invasive cancer called squamous cell carcinoma.

Squamous cell carcinoma in situ can develop anywhere in the body where squamous cells are normally found including the skin, oral cavity, esophagus, and lungs. This condition can also develop in areas of the body where squamous cells are not normally found but where they arise after periods of long-standing inflammation from a process called squamous metaplasia.

What causes squamous cell carcinoma in situ?

The cause of squamous cell carcinoma in situ varies based on the tumor’s location. Long-term and excessive exposure to UV radiation, usually from the sun, causes most skin tumors. Tobacco smoke is a common cause of tumors in the oral cavity, larynx, esophagus, and lungs. Additionally, medications or immune disorders that suppress the immune system increase the risk of developing this condition in both the skin and internal sites.

What does squamous cell carcinoma in situ look like under the microscope?

Under the microscope, this non-invasive type of cancer is made up of large abnormal-looking squamous cells that replace the healthy squamous cells normally found in the epidermis (for skin tumours) or the epithelium (for tumours in other parts of the body). The tumour cells often have large atypical (abnormal) shaped nuclei. that may be described as hyperchromatic (darker than normal) or pleomorphic (varying in shape and size). Mitotic figures (cells dividing to create new tumour cells) are also commonly seen.

squamous cell carcinoma in situ

About this article

Doctors wrote this article to assist you in reading and comprehending your pathology report. Feel free to reach out to us with any questions about this article or your pathology report. To get a comprehensive introduction to your pathology report, read this article.

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