Cindy Y.L. Khu¹, Sureshni I. Jayasinghe^1,2, Christina Foley³, Stephen B. Fox^4,5

¹Department of Anatomical Pathology, St. Vincent’s Hospital Melbourne, Australia; ²Department of Clinical Pathology, The University of Melbourne, Melbourne, Australia; ³Department of Surgery, St. Vincent’s Hospital Melbourne, Australia; ⁴Department of Pathology, Peter MacCallum Cancer Centre, Melbourne, Australia; ⁵Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Australia

A 73-year-old female presented with a breast mass, diagnosed on core biopsy as an atypical papillary neoplasm. Subsequent excision demonstrated a lobulated infiltrative biphasic tumour of atypical epithelial and myoepithelial components with prominent squamous metaplasia and clear cell change. Triple-negative immunophenotype and >50% Ki-67 proliferative index were found. A diagnosis of M-AME with in-situ and invasive M-AME components was rendered. This was supported by molecular changes including biallelic inactivation of PIK3R1 (p.P70fs and p.1571_K575del) and biallelic activating FGFR2 (p.K659E and p.N549H).

M-AME is defined as AME with carcinoma of either the luminal or myoepithelial component, or of both types, a rare entity with a paucity of data in the literature. It has been proposed to further classify M-AME into M-AME in-situ, M-AME invasive and AME with invasive carcinoma, to reflect their distinct behaviour and guide individualised management. M-AME invasive is likely to behave in a more indolent manner than AME with invasive carcinoma. Metastases have been reported in M-AME with haematogenous spread, and less frequently, via lymphatics. Complete excision is currently recommended for M-AME, and adjuvant therapy has not proven to be effective. M-AME with a distinct carcinoma of luminal component should be managed according to standard breast cancer protocols.

 

1. Rakha E, Tan PH, Ellis I, Quinn C. Adenomyoepithelioma of the breast: a proposal for classification. Histopathology. 2021 Oct;79(4):465-479. doi: 10.1111/his.14380. 

2. Xu J, Tang X, Iida Y et al. Adenomyoepithelioma with carcinoma of the breast: a report of two cases and a review of the literature. Pathol. Res. Pract. 2016; 212; 130–134.

3. WHO Classification of Breast Tumours. 5th Edition. IARC. 2019.

 

Author CYLK conducted the literature review and compiled the abstract. 

Author SIJ reported the case, reviewed the literature and contributed to the content included in the abstract.

Author CF was the clinician involved in surgical care for the patient and contributed to the content included in the abstract.

Author SBF provided second opinion for the original reporting of the case and generated the molecular findings contributed to the content included in the abstract.