Because the technique of specimen processing impacts on the incidence of positive surgical margins, a standard technique using 2-3 mm sections has been described by True in the hope of improving the likelihood of detecting positive margins. A positive surgical margin is defined as the presence of tumor cells at the inked surgical margin of resection. The margin extent is classified as focal, extensive or equivocal. A focal margin is defined as a margin present in only one step section and involving one gland in that section. Involvement greater than this is classified as an extensive margin. An equivocal margin is used to describe tumor cells in contact with ink in the absence of periprostatic tissue. This phenomenon occurs at the site of hemostatic clips and sharp dissection close to the capsule.9
The location of the positive surgical margin is classified as apical, anterior, bladder neck, posterolateral or posterior. Bladder neck or apical margins are identified as being present if tumor is in contact with ink in the respective zones. The posterior surface represents the concave aspect of the gland in contact with the rectal surface. The anterior surface describes the corresponding width of the gland anteriorly. Remaining lateral aspects of the gland are designated as posterolateral, lying between these two surfaces. The posterolateral segment includes the area next to the neurovascular bundles.
Extracapsular perforation is defined as the presence of neoplastic cells in contact with periprostatic fat, connective tissue, or into adjacent bladder or skeletal muscle, which may be associated with positive surgical margin. If the positive surgical margin occurs in an area without periprostatic tissue, this is designated a positive surgical margin.
The positive margin rate is highly dependent on the technique the pathologist uses to process and evaluate the radical prostatectomy specimen. For example, different methods of processing the apical region may result in varying incidences of positive surgical margins.10 Voges etal. made the distinction between positive surgical margins due to incision into the prostate versus those due to capsular penetration.11 They found that positive apical margins arising from small volume tumor (less than 4 cm3) were more frequently the result of incision into the prostate, and those arising from large volume tumors (greater than 12 cm3) were mostly due to capsular penetration. Capsular incision exposing benign tissue has not been associated with biochemical failure.12
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