IBF as a Formalin Substitute Fixative in Prostate Biopsy Pathology
Bibliographic record
Abstract
To the Editor.—We read with interest the study by Titford and Horenstein,1 who concluded that formalin fixation in comparison with 5 formalin substitutes provided the highest histomorphologic quality for 7 different surgical pathology specimens stained with hematoxylin-eosin. However, fixatives other than formalin are widely used in selected areas of surgical pathology practice because they provide for better evaluation of specific diagnostic criteria in different tissues and tumors (eg, B-Plus Fix in lymphomas).Optimal fixation of prostate biopsies is of utmost importance for biopsy evaluation. Most laboratories fix prostate biopsies in 10% neutral-buffered formalin, which often produces suboptimal, smudged, or blurred nuclear morphology. Nucleus-enhancing fixatives, such as Bouin and Hollande fixatives, are also used for prostate biopsy fixation and contain picric acid, which is biohazardous and potentially explosive when dry.2 Bouin fixative has been reported to decrease the immunoreactivity for cytokeratin.3 Since 1993, we have routinely fixed all prostate biopsies in our institution with IBF fixative (Surgipath, Richmond, Ill), which contains isopropyl alcohol, methanol, barium chloride, and low percent formalin (<3% by weight). Since 2000, we have processed more than 7000 prostate biopsies in IBF through our centralized urologic pathology practice in Calgary, Alberta. Prostate cores are typically placed in 30-mL containers with IBF immediately after the biopsy and are fixed between 3 and 24 hours in IBF, which is followed by routine processing. IBF-fixed prostate biopsies consistently exhibit excellent cellular morphology on hematoxylin-eosin staining. Prostate cancer glands demonstrate crisp nuclear morphology with clearly visible and prominent nucleoli, which is particularly helpful in establishing a diagnosis of high-grade prostatic intraepithelial neoplasia and small foci of prostatic cancer. Since other diagnostic features of prostatic cancer in IBF-fixed biopsies are identical to those seen in formalin-fixed biopsies, having an opportunity to see the nucleoli clearly in the atypical or suspicious glands may resolve pathologists' uncertainty about the presence of the nucleoli, which is often difficult to visualize in formalin-fixed biopsies. We do not find problems comparing the prominent nucleoli in the neoplastic glands with the inconspicuous or delicate nucleoli that may be seen in the adjacent benign glands.Obviously, it is also paramount to deal with other common technical pitfalls, such as thick and overstained sections that obscure the nuclear morphology. High-molecular-weight cytokeratin (34βE12 or keratin 903), which stains the basal cells in prostatic glands, demonstrates variations of sensitivity and specificity, which are dependent on the duration of formalin fixation and the antigen retrieval technique.4 IBF-fixed prostate biopsies demonstrate preserved immunoreactivity for high-molecular-weight cytokeratin (for antibodies 34βE12 and cytokeratin 5/6) and for α-methylacyl-CoA racemase/P504S.5 Sectioning of IBF-fixed biopsies does not require additional time or technical skill in comparison to the similar formalin-fixed small biopsies (eg, liver and lung), and IBF has a comparable cost to formalin. In our experience, in addition to proper handling, processing, sectioning, and staining of the prostate biopsies, fixation in IBF improves the resolution of the cytologic and nuclear detail and preserves the immunoreactivity of the prostate biopsy tissue.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.008 | 0.023 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.002 | 0.003 |
| Scholarly communication | 0.004 | 0.004 |
| Open science | 0.005 | 0.001 |
| Research integrity | 0.009 | 0.016 |
| Insufficient payload (model declined to judge) | 0.003 | 0.005 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".