REVIEW 5 major objections 5 minor 15 references
A bag of tricks for real-time Mitotic Figure detection
T0 review · 5 major / 5 minor · reviewed 2026-08-05 · deepseek-v4-flash
Pith's one-line read A compact detector reaches F1 0.81 for mitotic figures across unseen domains
desk verdict Honest engineering note with one real but underspecified external result: F1 0.81 on MIDOG 2025 preliminary, yet the supporting ablations and protocol details are missing. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing mechanism is the three-level hierarchical sampling weight w(x_i)=w_D(d_i)·w_I(m_i)·w_C(c_i). Each factor is an inverse-frequency weight: dataset level, slide level, and class level (MF vs NMF), so every mini-batch draws roughly equally from all six sources, from different slides, and at a 1:1 mitotic/non-mitotic ratio. Around this, RTMDet-S is the compact real-time single-stage detector backbone; hard-negative mining adds extracted patches from necrotic and debris tissue as false-positive examples, and four EMA-smoothed weight copies are ensembled at inference with test-time augmentation.
What would settle it
Ask for the exact slide-level fold assignment and MIDOG submission identifiers, then check whether any specimen appears in both training and test folds; alternatively, rerun the same pipeline on the released final MIDOG 2025 test labels and compare the reproduced F1 to 0.81.
Extended reading notes
Core claim
On its own terms, the paper's central claim is that RTMDet-S, a small single-stage detector with a 64×64 anchor tuned to mitotic figures, reaches F1 0.81 on the MIDOG 2025 preliminary test set and F1 0.78–0.84 in grouped 5-fold cross-validation, outperforming larger RTMDet variants, Swin-L and ConvNeXt backbones, and a two-stage verification pipeline. The authors attribute the result to a three-level sampling weight that balances datasets, slides, and mitotic versus non-mitotic patches, plus HSV augmentation and hard negatives mined from necrotic and debris-labeled regions. They interpret the performance as evidence that careful training-data curation matters more than model capacity for dom
Load-bearing premise
The evaluation assumes the grouped fold split and the MIDOG test set never share a slide or patient with the training data; if they do, the reported F1 range overstates how well the model generalizes.
Editorial extensions
If this is right
- At 20–30 ms per 1920×1280 patch on an RTX 3090, a whole slide can be processed in minutes, making mitotic counting practical in a clinical workflow.
- Larger models and two-stage verification add cost without improving F1, so a well-trained small one-stage detector is enough for this task.
- Hard negatives from necrosis and debris reduce false positives, directly addressing the confounders that plague mitosis counting in real slides.
- The negative results for mosaic augmentation, stain normalization, and a second-stage classifier suggest that domain coverage and balanced sampling are the main levers for domain generalization here.
Reading between the lines
- The same recipe likely extends to other small-object histopathology detection tasks, such as counting other cell types, whenever domain shift and class imbalance dominate; that is an extrapolation, not a paper claim.
- The reported F1 of 0.81 rests on the preliminary MIDOG 2025 leaderboard; if the final test set reassigns labels or adds harder domains, the number could shift.
- Publishing the exact slide-level fold IDs would let others verify that no specimen overlaps train and test, and would make the 0.78–0.84 range reproducible.
- Hard-negative mining could be iterated: run the trained model on unlabeled clinical slides, harvest confident false positives, and retrain, potentially removing the need for manually annotated negative tissue.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes a 'bag of tricks' for real-time mitotic figure detection using the RTMDet-S single-stage detector. The main ingredients are: training on several public mitotic figure datasets spanning scanners, species, and tumor types; a three-level hierarchical sampling strategy balancing datasets, slides, and MF/NMF classes; targeted hard-negative mining from necrotic and debris regions; HSV jitter and geometric augmentation; an ensemble of EMA-smoothed models; and test-time augmentation. The authors report per-fold F1 scores between 0.78 and 0.84 in a grouped 5-fold cross-validation and an F1 of 0.81 on the preliminary MIDOG 2025 test set, with inference at roughly 20-30 ms per 1920x1280 patch on an RTX 3090. They also report negative results for mosaic augmentation, stain normalization, and a two-stage detector.
Significance. If fully substantiated, the result is practically significant: it would show that a compact one-stage detector, trained with carefully balanced multi-domain data and hard negatives, can match or exceed larger models on mitotic figure detection under domain shift while remaining real-time. The negative findings are also potentially useful to the community. However, the paper currently provides almost no quantitative ablation support for its own 'bag of tricks', and the headline external leaderboard result is described with insufficient protocol detail to be verified. The work is therefore best viewed as a challenge-report-level claim that needs substantial additional evidence before it can be accepted as a scientific paper.
major comments (5)
- [Abstract and Section IV] The central claim 'F1 of 0.81 on the MIDOG 2025 preliminary test set, outperforming larger models' is not verifiable from the manuscript. The paper does not define the challenge protocol: matching threshold, per-patch vs per-slide F1 computation, number of submitted entries, date of the leaderboard snapshot, or how 'larger models' are defined. No code, weights, predictions, or leaderboard excerpt are provided. Because the leaderboard is 'preliminary', the number is time-indexed and may change. Please provide the full protocol, the exact leaderboard table with ranks and total entries, and release code/weights or a reproducible inference script.
- [Section III, Hierarchical Sampling and Section IV, Results] The paper asserts that ablations showed the balanced sampling strategy was 'important', that larger RTMDet variants and Swin/ConvNeXt backbones were 'on par or slightly worse', and that mosaic augmentation, stain normalization, and a second-stage classifier were ineffective. None of these claims is accompanied by a single number, table, or error bar. For a paper whose contribution is a 'bag of tricks', the contribution of each trick is the central scientific content. Please provide an ablation table with mean and per-fold F1, precision, and recall for each component (e.g., sampling strategy, hard negatives, augmentation, EMA ensemble, TTA) and a comparison table of architectures.
- [Section IV, Evaluation and Results] The 'grouped, stratified 5-fold cross-validation' is under-specified. 'Grouped' is not defined; the paper does not state the grouping unit (slide, specimen, patient), how stratification was performed, or the number of specimens/slides in each fold. Without assurance that no specimen or patient appears in both training and test folds, the F1 range 0.78-0.84 cannot be interpreted as generalization to unseen slides. Please specify the grouping unit, report the fold compositions, and list per-fold F1, precision, and recall.
- [Section III, Hard Negative Mining] The hard-negative mining procedure is self-bootstrapping: the model's own low-confidence detections on necrotic/debris regions are selected as new NMF training examples. While the labels are derived from region annotations, the selection criterion is model-dependent and could reinforce the model's existing false-positive modes. The paper reports no ablation comparing mined vs random negatives and no details on the number of mined patches or potential overlap with the training set. Please provide this information and discuss how the self-selection affects the error profile.
- [Section III, Methods] The paper describes RTMDet as a 'one-stage anchor-based detector' and states that an 'appropriate anchor size (64×64 pixels)' was used. In its original formulation, RTMDet is an anchor-free detector. This is a substantive mischaracterization that affects reproducibility. Please clarify whether a non-standard anchor-based head was implemented, or whether 'anchor size' refers to a label-assignment prior; if the standard RTMDet was used, correct the description.
minor comments (5)
- [Section III, Eqs. (2)-(3)] The formulas for w_D and w_I include a summation over all datasets/images that does not depend on the current d or m; they reduce to a constant divided by |d| or |m|. If the intent is inverse-frequency weighting, write the normalized form and explain how the product of weights in Eq. (1) is converted into sampling probabilities.
- [Section IV, Inference Speed] The inference speed of 20-30 ms per patch is reported without measurement conditions. Please specify batch size, inference precision (FP32/FP16), framework, and whether preprocessing/TTA is included in the timing.
- [Datasets and References] The MIDOG 2025 challenge is not cited or described. Please add a citation or URL to the challenge specification, including the definition of Track 1 and the evaluation metric.
- [Throughout] Text formatting issues: '112.923 patches' uses a decimal-style separator; the abstract uses 'MItosis' with irregular capitalization; '1920×1280' appears inside a sentence without units. These should be corrected.
- [Section III, Augmentation] The augmentation ranges are given as 'e.g. ±10% hue variation, ±20% saturation, ±20% brightness'; 'e.g.' indicates the exact final values are not specified. Please state the exact ranges and any clipping applied.
Circularity Check
No significant circularity: the central F1=0.81 result is an external challenge score, and the proposed training tricks do not reduce to their inputs.
full rationale
The paper's central claim—F1=0.81 on the MIDOG 2025 preliminary test set—is an external benchmark result, not a quantity derived from the method's own equations or fitted parameters. The grouped 5-fold cross-validation (F1 0.78–0.84) is also evaluated on held-out slides, and the paper does not use those folds as training data for the final model. The training techniques described (Eqs. 1–4 balanced sampling, HSV/geometric augmentation, EMA ensembling) are standard and do not encode the evaluation metric or the test set. The hard negative mining step does use a trained RTMDet-S model to propose candidate patches from SPIDER and NCT-CRC-HE-100K, but the resulting examples are labeled as NMF only because they fall in regions annotated as necrotic or debris by those external datasets; the model supplies locations, not ground-truth labels, and these patches are not part of the MIDOG 2025 test set. This is a self-bootstrapping training loop, but it is not a circular prediction chain. Self-citations (refs 1, 2, 4, 6, 7, 8, 9, 12, 13) are dataset sources, prior baselines, or a sampling inspiration; none is a load-bearing uniqueness theorem or a forced ansatz. The paper does omit procedural details for the MIDOG 2025 leaderboard (metric definition, cohort composition, error bars) and does not define what 'grouped' means in the CV, but these are reproducibility/verification gaps, not circular reductions. No equation or fitted parameter is reused as a prediction, so I find no significant circularity.
Assumptions & free parameters
free parameters (7)
- anchor size =
64x64 pixels
- training patch size =
1920x1280 pixels
- training iterations =
25,000
- EMA decay rates =
1e-3, 5e-4, 2.5e-4
- hard negative confidence threshold =
0.25
- MF:NMF batch ratio =
1:1
- augmentation ranges =
±15 deg rotation; HSV ±10/20/20%; flips 50%
assumptions (4)
- domain assumption Mitotic figures are roughly constant in size across domains such that a 64x64 anchor at 40x magnification captures them.
- domain assumption Necrotic and debris patches from SPIDER and NCT-CRC-HE-100K contain no true mitotic figures.
- domain assumption The 'grouped' cross-validation split preserves slide/patient independence.
- domain assumption The MIDOG 2025 preliminary test set is an unbiased sample of unseen domains.
Cite this review
Pith. "Pith review of A bag of tricks for real-time Mitotic Figure detection." pith.science (2026). https://pith.science/paper/UZ5KVV7M
@misc{pith2026250819804,
author = {Pith},
title = {Pith review of: A bag of tricks for real-time Mitotic Figure detection},
year = {2026},
howpublished = {\url{https://pith.science/paper/UZ5KVV7M}},
note = {Machine review of arXiv:2508.19804}
}
read the original abstract
Mitotic figure (MF) detection in histopathology images is challenging due to large variations in slide scanners, staining protocols, tissue types, and the presence of artifacts. This paper presents a collection of training techniques - a bag of tricks - that enable robust, real-time MF detection across diverse domains. We build on the efficient RTMDet single stage object detector to achieve high inference speed suitable for clinical deployment. Our method addresses scanner variability and tumor heterogeneity via extensive multi-domain training data, balanced sampling, and careful augmentation. Additionally, we employ targeted, hard negative mining on necrotic and debris tissue to reduce false positives. In a grouped 5-fold cross-validation across multiple MF datasets, our model achieves an F1 score between 0.78 and 0.84. On the preliminary test set of the MItosis DOmain Generalization (MIDOG) 2025 challenge, our single-stage RTMDet-S based approach reaches an F1 of 0.81, outperforming larger models and demonstrating adaptability to new, unfamiliar domains. The proposed solution offers a practical trade-off between accuracy and speed, making it attractive for real-world clinical adoption.
Reference graph
Works this paper leans on
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Mitosis domain generalization in histopathology images–the midog challenge
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Reviewed August 5, 2026 · model on record in the stance chip above.
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