Ultrasound Features and Rate of Upgrade to Malignancy in Atypical Apocrine Lesions of the Breast

[Apocrine lesions of the breast]

Apocrine breast lesions encompass a spectrum of histopathological abnormalities, ranging from benign apocrine metaplasia to invasive apocrine carcinomas. Their defining feature lies in cells with abundant eosinophilic cytoplasm and round nuclei with prominent nucleoli. These cells strongly express the androgen receptor while lacking estrogen receptor-alpha and progesterone receptor expression. Benign lesions, frequently associated with mammary cysts or papillomas, lack nuclear and architectural atypia. In contrast, atypical apocrine lesions exhibit significant nuclear and structural abnormalities, posing diagnostic challenges when distinguishing them from apocrine ductal or lobular carcinoma in situ. Diagnosis relies on the extent of atypia and the presence of tumor necrosis. Invasive apocrine carcinomas are rare, accounting for less than 1% of all breast cancers, and predominantly occur in postmenopausal women. Histologically, they are often grade 1 or 2 tumors. Approximately 50% exhibit HER2 amplification and overexpression. Immunohistochemically, they are characterized by positivity for FOXA1 and GATA3, and negativity for FOXC1 and SOX10, and variable expression of TRPS1. These carcinomas belong to the molecular apocrine carcinoma family, which includes HER2-enriched tumors driven by HER2 addiction and androgen receptor-positive luminal tumors, a subtype of triple-negative breast cancers. The latter are defined by androgen receptor pathway activation and are frequently associated with PI3K pathway alterations and cell cycle dysregulation, suggesting potential therapeutic targets.

Radiomics analysis combining gray-scale ultrasound and mammography for differentiating breast adenosis from invasive ductal carcinoma

Objectives

To explore the utility of gray-scale ultrasound (GSUS) and mammography (MG) for radiomic analysis in distinguishing between breast adenosis and invasive ductal carcinoma (IDC).

Methods

Data from 147 female patients with pathologically confirmed breast lesions (breast adenosis: 61 patients; IDC: 86 patients) between January 2018 and December 2022 were retrospectively collected. A training cohort of 113 patients (breast adenosis: 50 patients; IDC: 63 patients) diagnosed from January 2018 to December 2021 and a time-independent test cohort of 34 patients (breast adenosis: 11 patients; IDC: 23 patients) diagnosed from January 2022 to December 2022 were included. Radiomic features of lesions were extracted from MG and GSUS images. The least absolute shrinkage and selection operator (LASSO) regression was applied to select the most discriminant features, followed by logistic regression (LR) to construct clinical and radiomic models, as well as a combined model merging radiomic and clinical features. Model performance was assessed using receiver operating characteristic (ROC) analysis.

Results

In the training cohort, the area under the curve (AUC) for radiomic models based on MG features, GSUS features, and their combination were 0.974, 0.936, and 0.991, respectively. In the test cohort, the AUCs were 0.885, 0.876, and 0.949, respectively. The combined model, incorporating clinical and all radiomic features, and the MG plus GSUS radiomics model were found to exhibit significantly higher AUCs than the clinical model in both the training cohort and test cohort (p<0.05). No significant differences were observed between the combined model and the MG plus GSUS radiomics model in the training cohort and test cohort (p>0.05).

Conclusion

The effectiveness of radiomic features derived from GSUS and MG in distinguishing between breast adenosis and IDC is demonstrated. Superior discriminatory efficacy is shown by the combined model, integrating both modalities.

Challenges and Clinical Relevance of Modern Breast Pathology Reporting: Your Questions Answered

BACKGROUND

Breast pathology reporting, especially for breast cancer, has evolved through the years, from terse succinct diagnostic conclusions with scant histological details to the current comprehensive reporting guidelines issued by major pathology colleges and bodies, including the International Collaboration on Cancer Reporting. Pathology elements included in reporting guidelines are evidence based and contribute significantly to individualised and personalised patient management.

SUMMARY

This article is based on the lively interactive question and answer session that followed the breast pathology segment in the symposium jointly organised by the British Association of Urological Pathology, British Association of Gynaecological Pathologists, British Society of Gastroenterology and the Association of Breast Pathology, in November 2022, titled "Personalised histopathology reporting for personalised medicine."

KEY MESSAGES

The breast pathology session emphasised the clinical utility of breast pathology data items, incorporating a case-based approach by highlighting the relevance of pathology information in various clinical scenarios. This review included clinico-pathological discussion points on florid lobular carcinoma in situ, atypical apocrine adenosis, post-neoadjuvant chemotherapy reporting, atypical ductal hyperplasia presenting at the margin, flat epithelial atypia versus columnar cell change, papilloma on core needle biopsy, margin status, mucocele-like lesion, total duct excision/microdochectomy specimen, and anterior and nipple margins in skin-sparing mastectomy. Effective communication and regular involvement of pathologists in breast multidisciplinary tumour boards are crucial.

Apocrine lesions of the breast

Apocrine change is recognised in benign, atypical and malignant lesions of the breast. Apocrine metaplasia, a frequent finding in the breast of women over the age of 25 years, is most commonly seen in benign cysts with a simple or papillary configuration. Apocrine change is also recognised in other benign lesions including sclerosing adenosis, now known as apocrine adenosis. Apocrine atypia usually refers to cytological atypia in which there is at least threefold variation in nuclear size but architectural atypia may also occur. The distinction between atypical apocrine hyperplasia and non-high-grade apocrine ductal carcinoma in situ may be difficult due to the relative rarity of these entities and the lack of validated diagnostic criteria. Lobular carcinoma in situ (LCIS) with apocrine change is considered to be a variant of pleomorphic LCIS. An apocrine variant of encapsulated papillary carcinoma is also recognised. Apocrine change is described in invasive carcinoma, including no special type, lobular, micropapillary and mucinous variants. The recent WHO 2019 update recognises 'carcinoma with apocrine differentiation' as a special type breast carcinoma based on the presence of apocrine morphology in at least 90% of the tumour. Tumours with apocrine morphology are usually but not always hormone receptor negative. Human epidermal growth factor receptor 2 (HER-2) status is variable. Molecular studies have identified breast tumours with apocrine features and high expression of androgen receptor mRNA including 'luminal androgen receptor tumours' and 'molecular apocrine tumours'. The term 'pure apocrine carcinoma' has been proposed to describe an invasive carcinoma with apocrine morphology that is oestrogen and progesterone receptor negative and androgen receptor positive. HER-2 status may be positive or negative. This article reviews the pathology of benign, atypical and malignant apocrine lesions of the breast, with emphasis on diagnostic criteria including an approach to evaluation of apocrine lesions on needle core biopsy, and recent advances in our understanding of invasive apocrine carcinoma.