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Changes in mitotic rate and cell cycle fractions caused by delayed fixation
K Donhuijsen1, U Schmidt, H Hirche
1Department of Pathology, University of Essen, West German Tumor Center.
Human Pathology
|July 1, 1990
Summary
Delayed fixation of tumor biopsies significantly reduces accurate mitosis counts, impacting cancer diagnosis and prognosis. Early fixation is crucial for reliable assessment of malignancy grading.
Area of Science:
- Oncology
- Cell Biology
- Pathology
Background:
- Mitosis frequency and DNA content are vital for diagnosing and prognosticating malignant neoplasms.
- The impact of delayed biopsy fixation on these parameters remains unclear.
Purpose of the Study:
- To investigate the effect of delayed fixation on mitotic activity and DNA content in human soft-tissue sarcoma xenotransplants.
- To determine the optimal fixation time for accurate assessment of tumor cell proliferation.
Main Methods:
- Human soft-tissue sarcoma xenotransplants were fixed at varying intervals post-biopsy (5 minutes to 12 hours).
- Mitotic activity was assessed by counting mitotic figures, and DNA content was analyzed using flow cytometry.
- Two independent observers performed mitosis counts to ensure reproducibility.
Main Results:
- Mitotic counts decreased significantly with delayed fixation, averaging 10-13% lower after 3 hours and 39-46% lower after 12 hours.
- The reduction in mitosis counts was more pronounced in tumors with higher initial mitotic activity.
- Flow cytometry data showed only a minor increase in the G2 + M-phase fraction, with minimal changes in DNA content.
Conclusions:
- Delayed fixation, particularly beyond 3 hours, leads to a substantial underestimation of mitotic activity in soft-tissue sarcomas.
- While some decrease may be due to cell cycle completion, reduced identifiability of pyknotic figures is a major factor.
- Early fixation of tumor biopsies is essential for accurate mitosis counting and reliable grading of malignancy.