Myoepithelial Tumor Pathology in Breast Tissue

Myoepithelial tumours of the breast encompass a spectrum of rare lesions characterised by proliferation of myoepithelial cells, often in conjunction with epithelial elements. These biphasic neoplasms range from benign adenomyoepitheliomas to malignant forms that demonstrate invasive potential and occasional distant metastasis. Histologically, they may assume tubular, lobulated, spindle‐cell or adenosis patterns, with cellular atypia, mitotic activity and necrosis serving as indicators of malignancy. Immunohistochemistry plays a central role in diagnosis, employing markers such as p63, calponin and smooth muscle actin to distinguish myoepithelial components. From a molecular standpoint, adenomyoepitheliomas exhibit genetic heterogeneity: oestrogen receptor‐positive variants frequently harbour PIK3CA or AKT1 mutations, while oestrogen receptor‐negative tumours often feature recurrent HRAS Q61 hotspot mutations co‐occurring with PI3K pathway alterations. Clinical management depends on accurate classification, complete surgical excision with clear margins and, in malignant cases, consideration of adjuvant therapy. Given their rarity and diagnostic complexity, centralised review by specialist pathologists is recommended to guide prognosis and treatment decisions.

Research from Nature Portfolio

Recent studies have elucidated the genetic drivers underpinning adenomyoepithelioma. Whole‐exome and targeted sequencing revealed that oestrogen receptor‐negative lesions harbour highly recurrent HRAS Q61 mutations alongside PIK3CA or PIK3R1 alterations. Functional assays in two‐ and three‐dimensional cell culture demonstrated that introduction of HRASQ61R, particularly in concert with PIK3CAH1047R, induces transformation, myoepithelial marker expression and enhanced AKT signalling. These findings establish HRAS Q61 mutations as probable oncogenic drivers distinct from those seen in common breast cancers and offer a molecular basis for diagnostic stratification and potential targeted interventions.

Myoepithelial Tumor Pathology in Breast Tissue publication trend

The graph below shows the total number of articles in myoepithelial tumor pathology in breast tissue across all publications each year (not limited to Nature Index journals).

Technical terms

Myoepithelial cell: Contractile cell type surrounding ducts and acini in glandular tissue, identified by markers such as p63 and calponin.

Adenomyoepithelioma: Rare biphasic breast tumour with mixed epithelial and myoepithelial proliferation, varying from benign to malignant.

Immunohistochemistry: Laboratory technique that uses antigen–antibody interactions to detect specific proteins in tissue sections, aiding tumour classification.

Hotspot mutation: Recurrent point mutation at a specific codon (e.g. HRAS Q61) implicated in oncogenic activation and tumour development.

References

1. Recurrent hotspot mutations in HRAS Q61 and PI3K-AKT pathway genes as drivers of breast adenomyoepitheliomas. Nature Communications (2018).
2. Adenomyoepithelioma of the breast: a proposal for classification. Histopathology (2021).
3. Triple-negative breast carcinomas of low malignant potential: review on diagnostic criteria and differential diagnoses. Virchows Archiv (2021).