Invasive lobular carcinoma (ILC) is a distinct type of breast carcinoma and represents 5-15% of invasive breast carcinomas in female. However, the occurrence of ILC is exceptional in male breast, and the incidence is 1.5-1.9% of male breast carcinomas. Herein, we report a case of pleomorphic lobular carcinoma in a male breast. A 76-year-old Japanese male with a history of treatment with a progestational agent for prostate cancer presented with a right breast tumor. Magnetic resonance imaging showed gynecomastia of bilateral breasts and an irregular-shaped nodule in his right breast. Histopathological study revealed infiltrative neoplastic growth of discohesive tumor cells arranged in single-filed linear cords or trabeculae. These neoplastic cells had variable-sized large nuclei containing occasional nucleoli. Immunohistochemically, these tumor cells lacked E-cadherin expression. Accordingly, an ultimate diagnosis of pleomorphic lobular carcinoma was made. This is the third documented case of pleomorphic lobular carcinoma of male breast. Our analyses of the clinicopathological features of this type of tumor revealed that patients were middle-aged or elderly men, and all cases were free from lymph node metastases or recurrence. Gynecomastia and a history of hormonal agent intake were present only in the current case. The most commonly proposed risk factor for the development of male breast cancer is elevated level of estrogen, and a possible link between the development of male breast cancer and estrogen therapy for prostate cancer has been suggested. The clinicopathological features of ILC of male breast remains unclear; therefore, additional studies are needed to clarify them.
Keywords: Lobular carcinoma; male breast; pleomorphic variant.