At what stage is a squamous cell carcinoma typically classified?

Squamous cell carcinoma (SCC) is typically classified at the stage of either "in situ" or "invasive." This classification is crucial because it indicates the progression of the disease.

When SCC is described as "in situ," it refers to carcinoma that has not penetrated beyond the basal layer of the epidermis. This means the cancerous cells are still confined to their original location and have not invaded deeper tissues. Once SCC penetrates the basement membrane and spreads into the surrounding tissues, it is termed "invasive," reflecting a greater potential for spread and requiring more aggressive management.

The other classifications provided do not fully encompass the range of SCC stages. While localized cases exist, SCC can progress to invasive forms, thus it wouldn't be accurate to exclusively classify it as "localized only." Metastatic classifications indicate further progression beyond the primary site, which is not applicable to all SCC cases, particularly those diagnosed early. The term "precancerous" generally refers to conditions like actinic keratosis which may lead to SCC but does not classify the carcinoma itself.

Ultimately, the classification of squamous cell carcinoma as either "in situ" or "invasive" provides a clearer understanding of its biological behavior, treatment options, and prognosis.