Introduction: Breast cancer (BC) proliferative activity is a significant predictive factor associated with treatment response and can be regarded as a proxy measure of tumor aggressiveness. Aims: The goal of research on atypical breast cancer is to comprehend, identify, and treat uncommon or uncommon breast cancers that differ from their conventional presentations, guaranteeing precise diagnosis and suitable therapy. Materials & Methods: The present study was a Case-Control Study. This Study was conducted from One year. Total 120 patients were included in this study. Result: There was a significant association between high atypical mitoses and high grade, larger tumor size, NST tumor type, the poor prognostic NPI group and TNBC phenotype. A significant association was confirmed between high overall mitotic count (>21 mitoses per 3 mm2) and other parameters characteristic of aggressive tumor behavior including high tumor grade, larger tumor size, NST histological type, the moderate and poor prognostic NPI groups and (TNBC) phenotype. Conclusion: We came to the conclusion that atypical breast tumors are a broad category of uncommon and uncommon cancers that differ from their usual appearances, which complicates diagnosis and treatment.
One significant predictive factor associated with the response to treatment is the proliferative activity of breast cancer (BC), which can be regarded as a surrogate indicator of tumor aggressiveness [1]. The gold standard assessment approach for determining the proliferative status of BC is the visual quantification of mitotic figures in hematoxylin and eosin (H&E) stained BC histological sections, which is known as the mitotic score. Furthermore, it is a crucial part of the Nottingham Grading System [2].
Two types of mitotic figures exist: normal and atypical. Atypical mitosis occurs when there is an odd, dysregulated, and haphazard nuclear material assembly in the dividing cells. This leads to aberrant mitotic morphology, which in turn reflects underlying genetic problems such aneuploidy, chromosomal instability, and telomere dysfunction. It is well accepted that the existence of aberrant mitotic figures is a characteristic of cancer and has predictive significance for some tumor types, including pancreatic and urothelial carcinomas. Validation studies and characterisation of the atypical mitoses score in BC are still missing, despite the fact that certain research using a small number of patients have revealed a link between atypical mitoses and poor outcomes in BC [3].
We postulated in our work that aberrant mitoses in BC have additional prognostic value. Using digitalized whole slide images (WSIs), we have visually quantified atypical mitoses in a large cohort of BC patients in order to evaluate the association between atypical mitoses and patient outcomes. Additionally, we made use of The Cancer Genome Atlas (TCGA) BC dataset's publically accessible RNA sequencing data (RNA-Seq) [4] to relate atypical mitoses to the underlying molecular changes and pathways. The goal of research on atypical breast cancer is to comprehend, identify, and treat uncommon or uncommon breast cancers that differ from their conventional presentations, guaranteeing precise diagnosis and suitable therapy.
Study Type (Design): Case-Control Study.
Study Period: One year.
Sample Size: 120
Inclusion:
Exclusion:
Statistical Analysis:
For statistical analysis, data were initially entered into a Microsoft Excel spreadsheet and then analyzed using SPSS (version 27.0; SPSS Inc., Chicago, IL, USA) and GraphPad Prism (version 5). Numerical variables were summarized using means and standard deviations, while categorical variables were described with counts and percentages. Two-sample t-tests, which compare the means of independent or unpaired samples, were used to assess differences between groups. Paired t-tests, which account for the correlation between paired observations, offer greater power than unpaired tests. Chi-square tests (χ² tests) were employed to evaluate hypotheses where the sampling distribution of the test statistic follows a chi-squared distribution under the null hypothesis; Pearson's chi-squared test is often referred to simply as the chi-squared test. For comparisons of unpaired proportions, either the chi-square test or Fisher’s exact test was used, depending on the context. To perform t-tests, the relevant formulae for test statistics, which either exactly follow or closely approximate a t-distribution under the null hypothesis, were applied, with specific degrees of freedom indicated for each test. P-values were determined from Student's t-distribution tables. A p-value ≤ 0.05 was considered statistically significant, leading to the rejection of the null hypothesis in favour of the alternative hypothesis.
Table 1: Relationship between atypical mitoses, atypical-to-typical mitoses ratio and clinicopathological parameters.
Categories |
Number (%) |
Low atypical mitoses ≤ 4 |
High atypical mitoses > 4 |
X2 P value |
Low ratio ≤ 0.27 |
High ratio > 0.27 |
X2 P value |
Tumor size |
|||||||
≤2 cm |
487 (58%) |
289 (59%) |
198 (41%) |
22.4 |
267 (55%) |
220 (45%) |
10.2 |
>2 cm |
359 (42%) |
154 (43%) |
205 (57) |
<0.00 01 |
157 (44%) |
202 (56) |
<0.00 01 |
Tumor grade |
|||||||
Grade 1 |
75 (9%) |
73 (97%) |
2 (3%) |
229.3 |
66 (88%) |
9 (12%) |
126.3 |
Grade2 |
191 (23%) |
168 (88%) |
23 (12%) |
<0.0001 |
142 (74%) |
49 (26%) |
<0.0001 |
Grade 3 |
580 (68%) |
202 (35%) |
378 (65%) |
216 (37%) |
364 (63%) |
||
Histologic types |
|||||||
No special type (NST) |
639 (75%) |
268 (42%) |
371 (58%) |
115.4 |
269 (42%) |
371 (58%) |
71 |
Lobular |
53 (6%) |
44 (83%) |
9 (17%) |
<0.00 01 |
34 (64%) |
19 (36%) |
<0.00 01 |
Other special types |
116 (14%) |
102 (88%) |
14 (12%) |
93 (80%) |
23 (20%) |
||
Mixed NST |
38 (5%) |
29 (76%) |
9 (24%) |
28 (74%) |
10 (26%) |
||
Molecular subtype |
|||||||
Luminal |
380 (46%) |
293 (77%) |
87 (23%) |
117.5 |
260 (68%) |
120 (32%) |
93.4 |
Triple negative |
324 (40%) |
92 (28%) |
232 (72%) |
<0.0001 |
108 (33%) |
216 (67%) |
<0.0001 |
HER2+ |
116 (14%) |
44 (38%) |
72 (62%) |
45 (47%) |
71 (53%) |
||
Lymph node status |
|||||||
Negative |
533 (63%) |
285 (54%) |
248 (46%) |
0.6 |
273 (51%) |
260 (49%) |
0.6 |
Positive |
312 (37%) |
158 (51%) |
154 (49%) |
0.43 |
151 (48%) |
161 (52%) |
0.4 |
Lymphovascular invasion |
|||||||
Absent |
576 (68%) |
305 (53%) |
271 (47%) |
0.3 |
304 (53%) |
272 (47%) |
5.1 |
Present |
270 (32%) |
138 (51%) |
132 (49%) |
0.6 |
120 (44%) |
150 (56%) |
0.02 |
Nottingham Prognostic index |
|||||||
Good prognostic group |
160 (19%) |
149 (93%) |
11 (7%) |
132.3 |
133 (83%) |
27 (17%) |
86.1 |
Moderate prognostic group |
524 (62%) |
231 (44%) |
293 (56%) |
<0.0001 |
226 (43%) |
298 (57%) |
<0.0001 |
Poor prognostic group |
161 (19%) |
63 (39%) |
98 (61%) |
65 (40%) |
96 (60%) |
Fig. 1: Association Of Atypical-To-Typical Mitosis Ratio with Outcome
There was a significant association between high atypical mitoses and high grade, larger tumor size, NST tumor type, the poor prognostic NPI group and TNBC phenotype. A significant association was confirmed between high overall mitotic count (>21 mitoses per 3 mm2) and other parameters characteristic of aggressive tumor behavior including high tumor grade, larger tumor size, NST histological type, the moderate and poor prognostic NPI groups and (TNBC) phenotype. High atypical-to-typical mitoses ratio showed similar associations with clinicopathological parameters. Logistic regression analysis showed that overall mitoses and atypical mitoses are independently associated with tumor size and histologic tumor type regardless of the degree of tubule formation and pleomorphism score.
A significant association was confirmed between the overall mitoses score, but not atypical mitoses, and patient outcome in terms of shorter BCSS (p = 0.04) and DMFS (p = 0.03). However, when the ratio was considered, high atypical-to-typical mitotic ratio showed a strong association with poor outcome (p = 0.013).
Atypical mitoses are believed to represent genetic defects that underpin aggressive behavior and malignant phenotypes. They are distinguished by aberrant sister chromatid separation and aberrant mitotic spindle symmetry [5]. A thorough description of atypical mitoses in BC has yet to be established, nonetheless. The current investigation used two sizable, well-characterized cohorts to assess the molecular relevance and prognostic implications of atypical mitoses in BC. We postulated that predictive information from atypical mitoses, which are easily evaluated in routine histology specimens, is comparable to or superior to more expensive morphological and molecular prognostic indicators.
In a preliminary study of BC, we found that atypical mitoses are sparse in BC with low overall mitotic score[6], so in the current study, we sought to enrich our local cohort with cases rich in mitotic figures including BC cases that show mitotic grading scores 2 and 3. In the TCGA cohort, the whole cohort was assessed; therefore, the median number of overall mitoses was higher in the Nottingham cohort. Also, to avoid comparing BC with high atypical mitoses against BC with low overall mitoses scores that may bias the results as the findings may represent the mitotic activity rather than the atypicality of mitosis, we analyzed not only atypical mitoses but also the atypical-to-typical mitoses ratio. In this study, although atypical mitosis and overall mitosis showed strong associations with the histologic grade, which is expected as mitosis score is one of the grade components, our results showed that atypical mitoses had independent association with tumor size and histologic tumor type regardless the degree of tubule formation and pleomorphism score of the tumor. This highlights the clinical and biological importance of identification of atypical mitoses in BC.
Our findings demonstrated a strong correlation between a high atypical mitoses score and other parameters that are indicative of aggressive tumor behavior. They also showed that the atypical-to-typical mitoses ratio—which is particularly significant in the context of this study—as well as the overall mitotic score and the atypical mitoses score provide significant prognostic value. Since a cut-off point of 8–12 is typically used to distinguish score 1 from 2 overall mitoses based on the currently used microscopes, pathologists may be hesitant to use only 4 atypical mitoses for prognostic stratification of BC. Here, we show a cut-off point of 4 segregated atypical mitoses into low and high groups. For this reason, the atypical-to-typical mitoses ratio may be more practical, pragmatic, and reflective of the intrinsic proliferative and genomic molecular phenotype of the tumor.
Although atypical mitoses in and of themselves did not appear to be associated with outcome in the entire BC cohort, they did separate luminal BC subtypes into two different prognostic groups when the cohort was stratified into molecular sub-classes. In fact, a prior study demonstrated that the identification of atypical mitoses is a poor prognostic sign in BC, however it was carried out on a small cohort with scant clinical data [3]. Crucially, prognostic stratification was found in the TNBC subtype as well as in the luminal BC class and the entire cohort when the atypical-to-typical mitoses ratio was taken into account. Neither as a continuous variable nor as scores, the overall mitoses were not predictive in TNBC. The increased proliferative activity of TNBC and the combination of the tumors' genetic abnormalities and proliferative activity may be reflected in the ratio of atypical to typical mitoses.
Shorter survival was linked to BC with high total mitoses or high atypical-to-typical mitoses ratio in the chemotherapy-naïve group when the cohort was stratified by adjuvant treatment. In patients receiving chemotherapy, this connection vanished. This is probably due to the fact that BC with high proliferative activity responds better to chemotherapy, producing results that are comparable to those with low proliferation. Our findings demonstrated that, when BC was categorized according to molecular classifications, TNBC patients with low atypical-to-typical mitoses ratios fared significantly better with chemotherapy than those with high ratios. The results of TNBC patients with low atypical-to-typical mitoses ratios who did not undergo chemotherapy were identical to those of BC patients with high ratios. Patients with low ratios reacted effectively to chemotherapy and had noticeably higher life times than those with high ratios. When the total number of mitoses in this molecular class of BC patients was taken into account, this observation was not found. According to these results, individuals with high-risk TNBC who have a high ratio of atypical to typical mitoses have a limited response and, if at all possible, should be administered further medication.
There are elements to take into account, even if the use of molecular-based assays for prognostication in women with BC is still receiving a lot of interest and is probably going to continue for some time. The atypical-to-typical mitoses ratio, a morphological feature offered by the current study, can be used in conjunction with other established prognostic and predictive criteria to improve risk classification in BC and even replace the costly molecular assays. The evaluation of aberrant mitoses and their integration into prognostic and predictive AI-based algorithms is anticipated to offer a cost-effective risk assessment tool in the age of digital pathology and artificial intelligence. Furthermore, when precisely evaluated using reliable techniques, the actual performance of the available molecular tests is quite comparable to the known morphological and clinicopathological characteristics. When evaluated in well-fixed samples, a head-to-head comparison of the molecular assays in BC revealed comparable concordance values to those reported for histological grade and mitotic scores (Kappa scores = 0.39–0.55), with discordant results being noted in 41% of individuals [7]. Although an ideal test has not yet been found, it is now believed that molecular diagnostics are probably cost-effective. Furthermore, in contrast to morphological features like the one described in this study, the majority of widely accessible molecular tests are used on the uncertain risk BC group and perform poorly in the TNBC and HER2 positive subtypes. Furthermore, morphological and clinicopathological factors continue to be the primary prognostic indicators utilized in low- and middle-income nations due to financial constraints. Lastly, the available data suggests that the most effective strategy for achieving the best stratification is to combine genomic testing with clinicopathological factors, like the one described in this work [8].
The study found that 77% of the differentially expressed genes (DEG) were greater in tumors with atypical mitoses. These DEGs were linked to biological processes and mechanisms that included DNA breakdown, centrosome spindle and microtubule, chromosomal location and segregation, and micro-RNA. These results are in line with recent research that links aberrant mitoses to chromosomal abnormalities, aneuploidy, telomere malfunction, and genomic instability. According to certain research, the primary causes of atypical mitoses in cancer are chromosomal instability and telomere malfunction, and atypical mitosis may be regarded as a morphological indicator of chromosomal instability [9]. Furthermore, it was suggested that the occurrence of atypical mitotic figures is brought on by particular centrosomal changes in every tumor and might be regarded as a unique occurrence that could play a role in the development of cancer. One of the prevalent characteristics of cancer cells is aneuploidy, which is linked to poor clinical outcomes [10]. A malfunction in the mitotic process, which is necessary to separate duplicate chromosomes into daughter cells, could be the fundamental cause of aneuploidy in cancer. An important morphological indicator of the underlying chromosomal instability and aneuploidy of tumor cells may be atypical mitosis.
We came to the conclusion that atypical breast tumors are a broad category of uncommon and uncommon cancers that differ from their usual appearances, which complicates diagnosis and treatment. For a correct diagnosis, early detection using sophisticated imaging and biopsy procedures is essential. It is easier to create efficient treatment plans when one is aware of the unique clinical, histological, and genetic traits of these cancers. To improve patient outcomes and provide tailored therapy for individuals affected by these atypical forms of breast cancer, more research and better diagnostic methods are needed.