Tubular variant of mammary adenomyoepithelioma: Diagnostic challenges and cytomorphological correlation in two cases

Abstract

The authors describe the cytomorphologic features of two cases of tubular variant of adenomyoepithelioma of the breast that were first examined by fine-needle aspiration cytology (FNAC) and diagnosed as fibroadenoma. On retrospective review of the cytology, subtle features such as less cohesive epithelial clusters, intimate association of clusters of stromal cells with epithelial elements, a dominant population of plump-epithelioid naked (myoepithelial) cells, and occasional cells with intranuclear inclusions, were noted. Thus, these lesions can be diagnostically challenging and cannot be conclusively differentiated from either fibroadenoma or tubular adenoma cytologically and the pathologist may only be able to give a differential on FNAC. Recognition of the biphasic nature and the characteristic overall architecture of the tumors in combination with immunohistochemistry are essential to establish the correct diagnosis on biopsy. Although most tumors have a benign clinical course, rare instances of local recurrence, malignant transformation, and distant metastases have been reported. A complete excision with adequate margins would lower the chance of local recurrence.

Keywords: Adenomyoepithelioma; breast; fibroadenoma; fine-needle aspiration cytology; tubular adenoma; tubular variant.

Figure 1

(a) Well-circumscribed mass with gray-white homogenous appearance, (b) tubular variant of adenomyoepithelioma - dark staining cuboidal epithelial cells and outer prominent myoepithelial cells with clear cytoplasm (H and E, ×100) (inset – higher magnification shows bland nature of both epithelial and myoepithelial cells (H and E, ×200), (c) Fine-needle aspiration cytology smear with bland round epithelial cells closely admixed with abundant oval-spindled myoepithelial cells. No atypia is present (Pap stain, ×400) (d) Intranuclear inclusion (arrow) in few myoepithelial cells (Pap oil immersion)

Figure 2

(a) Cytokeratin positivity of ductal epithelial cells (cytokeratin, ×100), (b) epithelial membrane antigen positive epithelial cells (EMA, ×100), (c) Calponin positivity in myoepithelial cells (Calponin, ×100), (d) p63 positive staining in myoepithelial cells (p63, ×100)