Adenomyoepithelioma of the breast with unusual confounding diagnostic feature: a case report

Abstract

Background: Adenomyoepithelioma of the breast is an uncommon subtype of breast neoplasm that occurs in adults over a wide age range but most commonly in middle-aged and older adults. It usually presents as a solitary palpable mass or is detected on breast radiographic images. Histologically, it is a biphasic tumor with proliferation of both the epithelial and myoepithelial components of the glands, with variable types of tissue metaplasia.

Case presentation: A 64-year-old Saudi woman who underwent regular breast screening (mammogram) presented to our hospital following radiographic detection of a suspicious grouped microcalcification in the upper outer quadrant of her right breast on the mammogram. A wide local excision of the right breast lump was performed. Following histopathological examination of the breast lump, the final diagnosis was breast adenomyoepithelioma with mucoepidermoid/divergent differentiation, with no evidence of malignancy. About two years after the operation, a clinical follow-up conducted outside our hospital showed the development of ductal carcinoma in situ in the same breast.

Conclusion: Although the prognosis and the plan of treatment remains the same, our case highlights the complexities in making an accurate diagnosis between the various types of metaplasia within adenomyoepithelioma on one hand and the presence of mucoepidermoid differentiation in adenomyoepithelioma on the other.

Keywords: Adenomyoepithelioma; Metaplasia; Mucoepidermoid; Myoepithelial.

Fig. 1

The breast mammogram (cranio-caudal view) showing an interval development of a suspicious grouped microcalcification in the upper outer quadrant of the right breast, Breast Imaging-Reporting and Data System 4C. A Anterior, P Posterior

Fig. 2

Breast magnetic resonance imaging showing non mass-like clumped progressive enhancement of microcalcification in the right breast. RAH Right, LPF Left

Fig. 3

a Adenomyoepithelioma showing well-circumscribed nodule of proliferating glands (hematoxylin & eosin staining, magnification ×4). b Glands composed of bi-layered tubules with inner cuboidal luminal epithelial cells, and outer myoepithelial cells (hematoxylin & eosin stain, magnification ×200). c Sebaceous and apocrine metaplasia with occasional mucin-producing cells within the lesion (hematoxylin & eosin stain, magnification ×200). d Mucicarmine special stain demonstrates positive reactivity in the cytoplasmic mucin (mucicarmine special stain, magnification ×200)