Introduction: Malignant Adenomyoepithelioma (MAME) of the breast is a rare neoplasm characterized by proliferation of both epithelial and myoepithelial cells with malignant transformation of one or both components. Case: An 85-year-old female presented with an enlarging right sided breast mass. Ultrasound and mammography was suspicious and core needle biopsy suggested atypical AME so a wide local excision was performed. Histology demonstrated a 28mm MAME with malignant myoepithelial transformation. Margins were clear but narrow anteriorly. Immunohistochemistry was negative for ER/PR/HER2. Ki67 was up to 20% and there were frequent mitoses (20 per 10 HPF). The patient underwent adjuvant radiotherapy for narrow margin and high-risk factors after discussion in a multidisciplinary meeting. She remains disease-free at six months. Discussion: the morphological heterogeneity of MAME makes it difficult to rule out malignancy pre-operatively with biopsy alone so any biphasic neoplasm should undergo excision. Adequate margins reduces the risk of local recurrence and metastatic dissemination. Management of the axilla remains controversial because lymph node involvement is rare as it is thought to spread haematogeneously. There is inadequate evidence to suggest routine adjuvant therapy but it can be considered in patients with high-risk features. MAME has the potential for recurrence and metastasis so long-term surveillance is recommended, particularly if the lesion is greater than 20mm such as in ours. Conclusion: Its biological behaviour is not well understood and management remains controversial. Multidisciplinary approach is encouraged to formulate a unique individualized treatment plan for this rare malignancy.