Morphological and molecular changes of oestrogen receptor-positive breast cancer following bridging endocrine therapy: a United Kingdom multicentre study.

AIMS: Standard neoadjuvant endocrine therapy (NAET) is used for 6-9 months to downstage hormone-receptor-positive breast cancer. Bridging ET was introduced during the COVID-19 pandemic to delay surgical intervention. There are no data in the literature on the effect of short course therapy on tumour response. We aimed to analyse the effect of bridging ET and validate the previously proposed neoadjuvant ET pathological reporting criteria. METHODS AND RESULTS: This was a multicentre cohort of 256 patients who received bridging ET between March and October 2020. Assessment of paired pre- and post-NAET hormone receptors and HER2 and posttherapy Ki67 expression was done. The median duration of NAET was 45 days. In all, 86% of cases achieved partial pathological response and 9% showed minimal residual disease. Histological response to ET was observed from as early as day 6 posttherapy. Central scarring was noted in 32.8% of cases and lymphocytic infiltrate was seen in 43.4% of cases. Significant changes associated with the duration of ET were observed in tumour grade (21%), with downgrading identified in 12% of tumours (P < 0.001), progesterone receptor (PR) expression with switch to PR-negative status in 26% of cases (P < 0.001), and HER2 status with a switch from HER2-low to HER2-negative status in 32% of cases (P < 0.001). The median patient survival was 475 days, with an overall survival rate of 99.6%. CONCLUSIONS: Changes characteristic of tumour regression and significant changes in PR and HER2 occurred following a short course of NAET. The findings support biomarker testing on pretreatment core biopsies and retesting following therapy.

Pathological Changes Following Neoadjuvant Endocrine Therapy (NAET): A Multicentre Study of 391 Breast Cancers.

Oestrogen receptor (ER)-positive breast cancer (BC) is generally well responsive to endocrine therapy. Neoadjuvant endocrine therapy (NAET) is increasingly being used for downstaging ER-positive tumours. This study aims to analyse the effect of NAET on a well-characterised cohort of ER-positive BC with particular emphasis on receptor expression. This is a retrospective United Kingdom (UK) multicentre study of 391 patients who received NAET between October 2012 and October 2020. Detailed analyses of the paired pre- and post-NAET morphological changes and hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) expression were performed. The median duration of NAET was 86 days, with median survival and overall survival rates of 380 days and 93.4%, respectively. A total of 90.3% of cases achieved a pathological partial response, with a significantly higher rate of response in the HER2-low cancers. Following NAET, BC displayed some pathological changes involving the tumour stroma including central scarring and an increase in tumour infiltrating lymphocytes (TILs) and tumour cell morphology. Significant changes associated with the duration of NAET were observed in tumour grade (30.6% of cases), with downgrading identified in 19.3% of tumours (p < 0.001). The conversion of ER status from positive to low or negative was insignificant. The conversion of progesterone receptor (PR) and HER2 status to negative status was observed in 31.3% and 38.1% of cases, respectively (p < 0.001). HER2-low breast cancer decreased from 63% to 37% following NAET in the paired samples. Significant morphological and biomarker changes involving PR and HER2 expression occurred following NAET. The findings support biomarker testing on pre-treatment core biopsies and post-treatment residual carcinoma.

Caesarean section operation is not associated with myometrial hypertrophy-a prospective cohort study.

Maternity statistics of England in 2020 showed rise in Caesarean Section (CS) rate to 31%. Some studies correlated adverse gynaecological symptoms e.g. menstrual irregularities and pelvic pain to 'niche' formation at CS scar site. Niche formation was speculated to cause myometrial hypertrophy aggravating these symptoms. This was a prospective comparative histological study including 52 consecutive benign hysterectomy specimens which were categorised into 2 groups: (i) specimens with CS scar (n = 22), (ii) specimens with no CS scar (n = 30). Median (IQ range) uteri weight was 97.2grms (43.5-226) and 91.7grms (35.7-201.7) in study and control groups, respectively (p = .991). Mean (±SD) thickness of anterior myometrial wall was 18.7 mm (±3.6) and 19.4 mm (±4.5) in study and control groups, respectively (p = .58). Mean (±SD) thickness of posterior myometrial wall was 19.1 mm (±3.7) and 18.7 mm (±3.9) in study and control groups, respectively (p = .78). The assumption that CS scar causes myometrial hypertrophy was not demonstrated in this study.IMPACT STATEMENTWhat is already known on this subject? Maternity statistics world-wide show a continuous rise in the rate of Caesarean Section (CS) operation. The CS scar is assumed to be related to adverse clinical gynaecological symptoms such as intermenstrual bleeding, dysmenorrhoea, dyspareunia and chronic pelvic pain; however, the mechanism of this association is not clear. Further, little is known about the effects of CS scar on uterine wall morphology and function.What do the results of this study add? This study was the first prospective series in the literature to compare the uteri with scar with those without in respect of weight and myometrial wall thickness. It was not able to demonstrate the association between having CS scar and myometrial hypertrophy which was hypothesised to be the cause of adverse gynaecological symptoms. However, the microscopic examination of the CS scar revealed adenomyosis, haemorrhage and/or chronic inflammation in most cases.What are the implications of these findings for clinical practice and/or future research? The clinical implication of the histological changes shown in the CS scar requires large comparative clinical studies.

Malignant phyllodes tumour of the breast mimicking endometriosis.

A 63-year-old woman presented with a clinically malignant mass. Core biopsy showed features resembling endometriosis. The glands were GATA3 and oestrogen receptor positive consistent with mammary origin and had no myoepithelial layer. The excision also showed a fibroepithelial component with stromal overgrowth, frequent mitoses and invasive margin consistent with a malignant phyllodes tumour. KMT2D and SETD2 mutations were present in both the conventional phyllodes tumour and endometriosis-like areas and are also described in endometriosis raising interesting questions about these lesions. This unusual pattern is a potential diagnostic pitfall, so it is helpful to be aware of it.