T1c

T1c is a designation used in the TNM cancer staging system to describe a tumor that falls within the T1 category. The T and N and M components together express the size and extent of the primary tumor, regional lymph node involvement, and distant metastasis. T1c is a subclass of T1, but its exact meaning depends on the organ site and cancer type. In some contexts, T1c conveys a specific size range; in others, it may reflect a particular method of detection rather than size alone.

In breast cancer, for example, T1 is subdivided to reflect tumor size. T1c indicates a tumor greater than 1 centimeter but not more than 2 centimeters in its greatest dimension. This size range helps differentiate early-stage cancers and can influence treatment planning when considered alongside N and M status.

In prostate cancer, T1c has a different meaning: it refers to a tumor that is not palpable during a digital rectal examination and was discovered by needle biopsy, typically prompted by an elevated prostate-specific antigen (PSA). Here, the designation is more about detection method than tumor size.

Because T1c definitions vary by cancer type and edition of the staging guidelines, clinicians rely on site-specific AJCC/UICC criteria. T1c is used together with the N and M classifications to determine overall stage group and guide treatment decisions, prognosis assessment, and research reporting.