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Difficulty: HardPathology and Biopsy Interpretation

A 67-year-old man presents to the urology clinic to discuss the results of a recent 12-core transrectal ultrasound-guided prostate biopsy. The biopsy was performed after two consecutive elevated prostate-specific antigen (PSA) measurements (most recently 6.8 ng/mL) and a normal digital rectal examination. The pathology report confirms invasive prostatic adenocarcinoma in two cores from the right peripheral zone. The multidisciplinary tumor board is reviewing the histopathologic architecture to determine the International Society of Urological Pathology (ISUP) Grade Group, which is critical for deciding whether the patient is a candidate for active surveillance or requires definitive therapy. Which of the following microscopic architectural patterns specifically define a Gleason pattern 4 tumor? (Select all that apply)

  1. A
    Discrete, well-formed individual acini separated by abundant intervening stroma
  2. Cribriform proliferations presenting as large cellular nests with multiple punched-out luminaAnswer
  3. Irregularly fused microacinar structures that merge together without intervening stromaAnswer
  4. Small, poorly formed glands composed of ill-defined cellular clusters with rare luminaAnswer
  5. E
    Solid sheets and cords of atypical cells without any attempt at glandular lumen formation

Answer

The architectural patterns that define a Gleason pattern 4 tumor are cribriform proliferations, irregularly fused glands, and poorly formed glands.
Gleason grading of prostate adenocarcinoma is based purely on the architectural pattern of the neoplastic glands rather than nuclear atypia. Pattern 4 is characterized by loss of discrete glandular architecture, presenting in three main forms: 1) Cribriform glands, which are large cellular nests containing multiple punched-out lumina without intervening stroma; 2) Fused glands, where adjacent acini merge irregularly; and 3) Poorly formed glands, consisting of small, ill-defined clusters of cells. Identifying any of these features warrants at least a secondary pattern 4 assignment, upgrading the tumor to a minimum of ISUP Grade Group 2, which typically shifts the management recommendation away from active surveillance toward definitive local therapy.

Step-by-Step Solution

1
Analyze the clinical scenario and the specific diagnostic task required.
The scenario requires identifying the microscopic features that differentiate a Gleason pattern 4 prostate adenocarcinoma from other patterns to determine the ISUP Grade Group.
Accurate pathologic grading is the most critical prognostic factor and dictates management (e.g., active surveillance vs. definitive therapy) for localized prostate cancer.
2
Review the defining histopathologic criteria for Gleason pattern 4.
Gleason pattern 4 is characterized by three main architectural features: cribriform glands, fused glands, and poorly formed glands.
Recognizing these specific patterns differentiates grade 4 from grade 3 (discrete, well-formed glands) and grade 5 (solid sheets, comedonecrosis, or single cells).
3
Evaluate each option against the established Gleason grading criteria.
Cribriform proliferations, fused microacinar structures, and small poorly formed glands match pattern 4. Discrete individual acini match pattern 3. Solid sheets match pattern 5.
Applying the exact architectural definitions ensures accurate grading.

Key Concept

Gleason Grading System for Prostate Adenocarcinoma
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Topics

Pathology and Biopsy Interpretation

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