Pattern 1: circumscribed nodule, uniform well-formed medium-sized glands, with minimal adjacent stromal infiltration (key is circumscription).
- Using strict criteria, this pattern is exceedingly rare and controversial in current practice. (be wary in making diagnosis)
- Most described earlier (pre-immunohistochemistry era) were likely atypical adenomatous hyperplasias (AAH or adenosis).
- Also rare, usually seen in transition zone; seen incidentally and usually seen with other higher grades.
- Because of the need to appreciate the entire nodular or circumscribe growth, diagnosis of patterns 1 and 2 are rarely, if ever, made in needle biopsy; diagnosis made only in TUR or prostatectomy specimens.
- Glands in pattern 1 and 2 are larger than in pattern 3.