Bilateral male breast cancer is very rare, and the incidence is reported to be only 1.5% to 2% of all male breast cancers. The incidence of metachronous breast cancer is higher than that of synchronous breast cancer [6
]. Literature reviews on synchronous bilateral male breast cancer, using PubMed until August 2011, were performed, and 24 cases were searched [3
]. Sporadic single case reports of synchronous bilateral male breast cancer, associated with male potential hypogonadism, hyperprolactinemia, hormonal therapy due to prostate cancer, long standing gynecomastia, and chromosomal abnormality (XXY or 45,X/46,XY mosaic karyotype), have been reported [8
The most common presenting symptoms of male breast cancer are a painless lump, bloody nipple discharge, and nipple retraction. The most common sign of breast cancer in men is a firm, non-tender mass located in the subareolar area. Nipple discharge is more common in malignant rather than benign disease in men [4
Various risk factors for male breast cancer have been identified, including familial and genetic factors (BRCA2), radiation exposure, Klinefelter's syndrome (47, XXY), hormonal imbalance, obesity, and testicular disease (undescended testis, orchitis, orchectomy) [1
]. About 4% to 16% of male breast cancers are reported to be associated with BRCA2 mutation in population-based series [4
]. However, the role of BRCA1 mutation has not been clearly defined with regard to male breast cancer. Chromosomal studies revealed a normal male karyotype of 46XY, and genetic analyses for BRCA1/2 genes were normal in the case of our subject.
Undescended testis has been investigated as a risk factor for male breast cancer. According to one report, there is a 12-fold increased risk of breast cancer in patients with undescended testis [8
]. This may be the result of a hormonal imbalance caused by testicular dysfunction [12
]. Unilateral undescended testis usually does not induce abnormal level of LH and FSH due to compensatory growth of the remaining gonad [13
]. The elevated gonadotropin level in this case may have been due to hypogonadism caused by testicular dysfunction. Other testicular disorders, including mump orchitis, orchiectomy and testicular injury, have also been mentioned as risk factors for male breast cancer [12
Obesity in postmenopausal women and men has been considered a risk factor for breast cancer, due to conversion of testosterone to estradiol and androstenedione to estrone in peripheral adipose tissue. Several studies indicate that mean estradiol levels were higher in male breast cancer patients than in controls [1
]. The slightly elevated level of estrogen in this case might be attributed to the patient's mildly increased BMI. However, we cannot conclude that bilateral breast cancer developed due to this hormonal imbalance.
Accessory breasts, or polymastia, occur in 0.4% to 6% of females and 1% to 3% of males [14
]. A case of bilateral accessory breasts in the axilla, with nipples, in a male patient with bilateral synchronous breast cancer has not been described before. The clinical significance of accessory breasts in male breast cancer is unknown.
Male breast cancer is more prone to test positive for hormonal receptors, but less likely to show c-erbB-2 over-expression [15
]. Of the 24 cases of bilateral synchronous male breast cancer reported in the literature, 20 cases, including our case, were analyzed for hormonal receptors and c-erbB-2 status. The hormonal receptor (ER or PR) was positive in 14 out of 16 cases (87.5%), while c-erbB-2 was negative in all of the 7 cases that were analyzed [3
]. Unilateral and bilateral breast cancer in men showed similar hormonal status [4
]. There is no data comparing the outcomes of male breast cancer with regard to differences between unilateral and bilateral cases.
In conclusion, the rarity of bilateral breast cancer in men often makes us overlook the importance of examination of the contralateral breast. We should take into account the possibility of synchronous breast cancer in male breast cancer patients, especially in patients with an undescended testis and elevated estrogen levels. A thorough physical examination is recommended in such cases.