Mucinous carcinoma in a male breast.

Male breast cancer is rare as compared to female counterpart. Pure mucinous carcinoma is an extremely rare histological subtype representing less than 1% of male breast cancers. So far very few cases of pure mucinous carcinoma of male breast have been reported in the literature, most of which were diagnosed after surgical resection. Fine-needle aspiration cytology is a well-established procedure for the evaluation of female breast masses but the diagnosis of malignancy in aspirates from male breast masses is rare. We herein present one case of mucinous carcinoma of breast in a 75-year-old male diagnosed by fine-needle aspiration and confirmed by histopathology. After a follow-up of 12 months the patient is free of any recurrence or metastasis.

Introduction

The existing epidemiological data confirms the infrequency of male breast cancer (MBC) which represents approximately 1% of all breast cancers.[12] Overall, the epidemiology of MBC presents similarities with the epidemiology of female breast cancer. Men with BRCA-2 gene mutation are predisposed to develop breast cancer while those with BRCA-1 mutation are at a lesser risk.[3] Important risks in the development of MBC include conditions of estrogen–androgen imbalance such as testicular dysfunction, obesity and liver dysfunction. Environmental factor, such as exposure to ionising radiation, is a well-known risk factor in women as well as men.[45] Recently gynecomastia has been shown not to be a risk factor for MBC in several series.[56]

Case Report

A 75-year-old male presented with a subareolar hard mass in the left breast, fixed to the overlying skin for one-year duration. There was no history of nipple discharge or familial breast cancer. Ultrasonography (USG) breast showed a well-defined hypoechoic lesion with well-defined margins in the left subareolar region. Tumor showed a well-defined lesion on mammography. A diagnosis of benign breast disease was made and fine-needle aspiration cytology (FNAC) was advised. Subsequently FNAC was done using 22G needle. Both Giemsa and Papanicolaou staining were done. Smears showed abundant mucinous stroma in background with atypical cells seen lying in groups and also arranged linearly showing round to oval nuclei, regular nuclear margins and 1–2 prominent nucleoli. Possibility of mucinous carcinoma of breast (pure type) was suggested and biopsy was advised [Figures1a–b].

Figure 1

(a and b): FNAC smears demonstrating abundant mucinous stroma with scattered atypical cells (a: Giemsa, ×100) (b: Giemsa, ×400)

Chest radiograph, ultrasound of the abdomen and routine blood investigations were within normal limit. A left radical mastectomy including left axillary lymph node dissection was performed. Histopathology showed tumor cells arranged in nests and solid pattern floating in abundant extracellular mucin and thus confirmed the diagnosis of mucinous breast carcinoma [Figure 2]. Lymph nodes were free of tumor cells. Immunohistochemical staining for hormonal study were negative for estrogen and progesterone receptors.

Figure 2

Section showing tumor cells in nests and solid pattern floating in abundant extracellular mucin (H and E, x400)

Discussion

MBC constitutes less than 1% of all cancers in men.[1] Men present at an older age than women (median age of 64.5 years) and MBC incidence increases with an advancing age. The most frequent type (about 90%) is invasive ductal carcinoma. Pure mucinous carcinoma of the male breast is an extremely rare neoplasm.[7] Very few cases of primary mucinous carcinoma have been reported in male breast.

Histologically pure mucinous carcinoma can be classified as pure and mixed forms. Pure mucinous carcinoma usually presents as a round and well-circumscribed lesion on the mammography. On breast USG, the tumor has well-defined margins, and it is iso-echogenic relative to the fat surrounding the breast tissue.[8] Microscopically it shows variable amount of extracellular mucin surrounding the tumor cells. Mucinous carcinoma with invasive areas not surrounded by mucin is considered as a mixed mucinous carcinoma. The prognosis of pure mucinous carcinoma is much better than for mixed one.[9] Large studies done on male breast aspirates have found a very good diagnostic accuracy of FNAC in diagnosing male breast carcinoma, reaching more than 90%.[1011]

The main differential diagnoses of mucinous carcinoma are infiltrating lobular carcinoma with signet ring cells and mucocoele-like lesions. Former does not occur in males as males have no lactiferous apparatus.

Surgery remains the cornerstone of MBC treatment. The standard treatment of MBC is modified radical mastectomy combined with axillary lymph node dissection. However some authors suggest that nodal dissection may be unnecessary in pure mucinous carcinoma because of very low incidence of axillary nodal metastasis.[12] Sentinel lymph node biopsy may help to identify the need for axillary dissection. The most important determinants of survival are stage of the disease and lymph node involvement. The use of adjuvant hormonal therapy i.e. Tamoxifen confers a survival advantage in men positive for hormonal receptors. The benefit of adjuvant chemotherapy in MBC is not well established.

MBC seems to have better prognosis as compared to female counterpart.[5] The changes in the male breast may be easier to detect because men have less breast tissue. However the awareness of breast cancer in men is much lower as compared to women, therefore men do not perform regular self examination of breast or talk with their doctor about the disease.

Conclusion

Although pure mucinous carcinoma of the male breast is an extremely rare entity, it remains an important disease which should be recognized and managed timely. Any delay in management can affect the patient's survival. FNAC is a useful tool for diagnosis with a very high sensitivity and specificity but the gold standard is histopathology. More research is needed on MBCs as it is becoming more apparent that it is a different disease than its female counterpart. This recognition will provide better focused treatment strategies and an overall improved survival.