Pitfalls in the diagnosis of prostate adenocarcinoma from holmium resection of the prostate.

Purpose: Holmium laser resection of the prostate (HoLRP) provides tissue for histologic analysis that was not possible using previous coagulative laser prostatectomies. It was assumed that these tissue specimens would yield the same histologic information as specimens obtained by transurethal resection of the prostate and would be adequate for diagnosis of cancer. However, tissue subjected to laser treatment may sustain thermal injury, resulting in artifactual change. The aim of this study was to define the histologic characteristics of prostate tissue after holmium laser prostatectomy and the influence of thermal change on diagnosis of malignancy.

Materials and methods: All prostate tissue was examined after HoLRP. Examination included prostate-specific antigen (PSA) staining and immunostaining for high-molecular-weight cytokeratins. Histologic features are described.

Results: Thermal injury after HoLRP was more extensive than previously believed. Artifacts observed under low power consisted of glandular distortion and contraction with crowding. Higher magnification revealed clumping of the chromatin of the nucleus, resulting in hyperchromasia and irregularity of the nucleus and loss of polarity. These changes may be mistaken for malignant change. It will be difficult to detect malignancy in areas involved by thermal injury. When prostate cancer exists, grading of cancer will be affected by these artifacts. Uptake of immunohistochemical staining with PSA and high-molecular-weight cytokeratins is nonspecific in areas of injury, reducing their usefulness in these cases.

Conclusions: Detection of malignancy may be compromised by thermal injury occurring after HoLRP. Preliminary preoperative transrectal ultrasound-guided biopsies may still be necessary for diagnosis of malignancy.