tertiary Gleason grade
tertiary Gleason gradeA term of art referring to the presence of a small component of high-grade (e.g., Gleason grade-5) histological pattern of conventional prostate carcinoma, which is seen in a biopsy or resection of prostate tissue that has lower primary and secondary grades (e.g., Gleason score of 4 + 3 = 7). The significance of a high-grade tertiary component is uncertain, but generally believed to worsen the patient’s prognosis.
Tertiary Gleason is defined as either:
(1) Any small amount of Gleason grade-4 or -5 tissue in a specimen from a patient who otherwise has a Gleason score of 3 + 3 = 6 or lower; or
(2) Any small amount of Gleason grade-5 tissue in a specimen from a patient who otherwise has a Gleason score of 3 + 4 = 7, 4 + 3 = 7, or 4 + 4 = 8.
Patients who have Gleason scores of 9 or 10 can not, by definition, have a clinically significant, tertiary Gleason grade.