[Mucocele-like lesion of the breast-histopathology and fine needle aspiration cytology changes]

To elucidate the histopathology and fine needle aspiration cytology (FNAC) features of mucocele-like lesion (MLL) of the breast, and to establish the criteria in separating MLL from mucinous carcinoma on the basis of pre-operative FNAC.

Seven cases of MLL (5 benign and 2 malignant) were reviewed. The histology and FNAC features were compared with 14 cases of mucinous carcinoma examined in the same period.

All cases of MLL presented with breast lumps (1 case was detected by doctor after abnormal mammogram) and MLL patients are much younger (mean age 34.8 years for MLL and 67.9 years for mucinous carcinoma). Histologically, MLL are characterized by mucinous cysts which may rupture and discharge their contents into the surrounding tissue. The lining epithelium is bland and epithelial cells are rare in the mucin pool. Malignant MLL shows associated in-situ carcinoma. In contrast, mucinous carcinoma is formed by large mucin pools devoid of lining epithelium and contains mumerous tumor cells in the mucin pools. In all cases, grossly visible jelly-like mucous was obtained from FNA. Cytologically, all smears showed abundant mucous in the background. The most important fratures distinguishing benign MLL from mucinous carcinoma were scant cellularity, rare intact single tumor cell and tumor cells arranged in cohesive monolayered clusters lacking significant nuclear atypia.

Mucinous lesions of the breast can be divided into MLL and mucinous carcinoma based on the FNAC changes. Operative therapy can be performed for definite cases of mucinous carcinoma without further biopsy. However, excisional biopsy is advised in MLL for further separation into benign and malignant categories.