What are the four grades of tumor severity as described in the chapter on the integumentary system?

The four grades of tumor severity are: Grade I, where tumor cells are well differentiated; Grade II, with moderately or poorly differentiated cells; Grade III, where cells are poorly differentiated; and Grade IV, characterized by very poorly differentiated cells.

Tumor grading is based on how closely the tumor cells resemble normal tissue. Grade I tumors have cells that closely resemble the tissue of origin and retain some specialized functions, indicating a good prognosis. Grade II tumors show moderate differentiation, while Grade III tumors have poorly differentiated cells with significant abnormalities. Grade IV tumors are very poorly differentiated, grow rapidly, and have the poorest prognosis.