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Adenomyoepithelioma of the breast with squamous and sebaceous metaplasia.

Sir, Adenomyoepithelioma is an uncommon tumour which has been reported in the salivary gland, breast and skin. It is characterised by proliferation of both epithelial and myoepithelial components of glandular tissue. Tavassoli proposed three histological categories based on the microscopic appearance: spindle-cell, tubular and lobulated variants. Pia-Foschini and colleagues recently described adenomyoepitheliomas of the breast under a spectrum of salivary gland-like tumours, with possible low grade malignant behaviour. We report a case of adenomyoepithelioma in the right breast of an elderly Chinese woman, with accompanying squamous and sebaceous metaplasia histologically observed concurrently within the epithelial elements, an extremely rare occurrence. An 86-year-old woman presented to her medical practitioner with the complaint of recent increase in size of a right breast lump which apparently had been present for the past 20 years. There was associated non-cyclical pain and tenderness over the right breast. Physical examination disclosed a large mass occupying almost the entire right breast that was clinically suspicious of malignancy. No mammography was carried out. She was advised to undergo surgical excision. A trucut biopsy was performed with intraoperative frozen section consultation, for which a diagnosis of an atypical epithelial proliferative lesion with possible apocrine features was made. Due to the large size of the mass, a surgical decision was made to carry out a simple mastectomy without axillary clearance. The right mastectomy specimen received by the pathology laboratory contained an overlying ellipse of skin and a small axillary tail. The nipple was everted and grossly unremarkable. Sectioning the breast revealed a large haemorrhagic cyst measuring 8 cm (medial-lateral)68 cm (supero-inferior)65 cm (antero-posterior) straddling the central region of the specimen and extending close to the superior and inferior radial margins. Contained within the cystic cavity were large amounts of friable and necrotic haemorrhagic material together with a pale yellow, firm, irregular tumour measuring 2.5 cm (medial-lateral)64 cm (supero-inferior)63 cm (antero-posterior). The tumour was attached to the cyst wall. Also received was a detached piece of tumour tissue measuring 36261 cm, which had likely separated from the main tumour. Microscopically, the trucut core biopsy sections from the right breast showed a proliferative epithelial lesion composed of bilayered tubules that were closely apposed. No convincing apocrine metaplasia was observed. The right mastectomy showed a large cyst that demonstrated focal areas of haemorrhage, haemosiderophages and organising haematoma in its fibrotic wall (Fig. 1A). Attached to the cyst wall was a solid, well-circumscribed tumour composed of almost back-to-back tubules that were lined by an inner secretory cuboidal cell layer and bounded by an outer myoepithelial layer, similar to that observed on the trucut biopsy (Fig. 1B). The nuclei of the luminal epithelial cells