Final Diagnosis -- Malignant Adenomyoepithelioma

FINAL DIAGNOSIS

Malignant Adenomyoepithelioma.

DISUCSSION

Adenomyoepitheliomas (AMEs) are rare, biphasic neoplasms containing both luminal epithelial cells and myoepithelial cells (1-5). They exist in the spectrum of biphasic breast neoplasms, which also include pleomorphic adenomas and adenoid cystic carcinomas (1-5). These neoplasms typically present as a painless breast mass, with the average age of diagnosis in the 60th decade (1-5). These neoplasms can also rarely occur in men (6). As in normal breast parenchyma, the luminal epithelial cells of AMEs stain with epithelial immunohistochemical stains, such as cytokeratin 7 and epithelial membrane antigen, whereas the myoepithelial cells stain with myoepithelial markers, such as p63, S-100, and smooth muscle myosin heavy chain (1-6).

They typically exhibit benign behavior but either the epithelial or mesenchymal components can undergo malignant transformation into an epithelial carcinoma, a myoepithelial carcinoma, or an epithelial-myoepithelial carcinoma (1-7). Malignant AME is a synonym for AME with carcinoma. Histologic evidence of malignancy includes cellular pleomorphism, mitotic activity, necrosis, overgrowth of either myoepithelial or epithelial component and invasion at the periphery of the tumor (8). The majority of AMEs can be treated by local excision, even though local recurrence may occur. In some cases, metastases to lymph nodes and to the lungs have been reported (6,7). A carcinoma arising in a malignant AME should be managed as any other type of breast carcinoma of similar grade and stage.

The patient had subsequent sentinel axillary lymph node biopsies, which showed benign lymph nodes. She underwent adjuvant chemotherapy with four cycles of adriamycin and cyclophosphamide with pegfilgrastim, followed by weekly paclitaxel, which she tolerated well.

REFERENCES

1. Tavassoli FA. Myoepithelial lesions of the breast. Myoepitheliosis, adenomyoepithelioma, and myoepithelial carcinoma. Am J Surg Pathol. 1991 Jun;15(6):554-68.
2. Rosen PP. Adenomyoepithelioma of the breast. Hum Pathol. 1987 Dec;18(12):1232-7.
3. Kim MJ, Kim CS, Ju MJ, Park YS. Malignant adenomyoepithelioma of the breast: A rare case report. Int J Surg Case Rep. 2019;59:111-114. doi:10.1016/j.ijscr.2019.04.045
4. Ito R, Ota D, Ando S, Mori M, Fukuuchi A. A case of adenomyoepithelioma with myoepithelial carcinoma of the breast. Clin Case Rep. 2019;7(5):930-934. Published 2019 Mar 30. doi:10.1002/ccr3.2100
5. Baum, Jordan E., et al. Mammary Epithelial-Myoepithelial Carcinoma: Report of a Case With HRAS and PIK3CA Mutations by Next-Generation Sequencing. Int J of SurgPath. 2019; 27(4): 441-445. doi:10.1177/1066896918821182.
6. Zhong E, Cheng E, Goldfischer M, Hoda SA. Papillary Lesions of the Male Breast A Study of 117 Cases and Brief Review of the Literature Demonstrate a Broad Clinicopathologic Spectrum. Am J Surg Pathol. 2019 Aug 9. doi: 10.1097/PAS.0000000000001340.
7. Trojani M, Guiu M, Trouette H, De Mascarel I, Cocquet M. Malignant adenomyoepithelioma of the breast. An immunohistochemical, cytophotometric, and ultrastructural study of a case with lung metastases. Am J Clin Pathol. 1992 Dec;98(6):598-602.
8. Syed A. Hoda, Edi Brogi, Fred Koerner, Paul Peter Rosen. Rosen's Breast Pathology, 4th edition. Lippincott Williams & Wilkins, Feb 5, 2014.

Contributed by Terri E. Jones, MD and Jing Yu, MD, PhD