Abstract
Pleomorphic adenoma is a common tumor encountered in major salivary gland and very rarely seen in breast. This matrix producing tumor can be confused with fibroadenoma, phyllodes tumor and metaplastic carcinoma on fine needle aspiration cytology(FNAC). Pre-operative diagnosis of pleomorphic adenoma helps in preventing surgical over or under treatment of the disease. We present an extremely rare case of pleomorphic adenoma of breast diagnosed on FNAC with histopathological confirmation.
Introduction
Pleomorphic adenoma(PA) which is commonly seen in parotid gland can occur very rarely in breast leading to misdiagnosis [1]. It was first described in 1969 by Smith and Taylor [2]. Since then around eighty cases have been published in literature in which very few have described the cytological features of the tumor [3]. PA possibly starts as an intraductal papilloma or adenomyoepithelioma. The myoepithelial cells of the papilloma are extraordinarily stimulated resulting in formation of the characteristic stromal elements [4,5].
Case report
A 39 year old female presented to our hospital with a lump in the right breast for the last three months. The left breast and both axilla were normal. Systemic examination was within normal limits. She was evaluated with Fine Needle aspiration cytology (FNAC). On FNAC, the right breast lump showed monolayered small to medium sized clusters of monotonous epithelial cells with uniform round nuclei in abundant chondromyxoid matrix along with dyscohesive plasmacytoid cells and cyst macrophages [Fig. 1a and b] Cytological diagnosis was given as benign phyllodes/ cystic disease of breast. She subsequently underwent lumpectomy with adequate margins of the breast lump. Grossly, well circumscribed firm mass measuring 20 mm × 10 mm × 8 mm with heterogeneous cut surface having solid whitish areas and semitranslucent bluish areas [Fig. 2a].
Histopathological examination revealed tumor composed of acini and spindle cells embedded in myxoid matrix with foci of ossification and mature cartilagenous tissue [Fig. 2b]. A final diagnosis of pleomorphic adenoma of the breast was made.
Discussion
Benign PAs of the breast have been mistaken for fibroadenoma, phyllodes tumor and metaplastic carcinoma on FNAC. The diagnosis is however usually made post operatively on final histopathological examination [1,3]. As in our present case, most tumors of PA occur in the right breast rather than left and has the tendency to occur in the sub-areolar region, suggesting that it originates from the large duct [6]. From 1969 to the present date, 73 cases have been reported but rarely in Asian individuals. Differences in lactation habits between Asian and western women may be the reason [7]. Pleomorphic adenoma should be considered in the differential diagnosis of breast lesion with both non-cohesive epithelial clusters and large deposits of eosinophilic- red material on FNAC [8]. Plasmacytoid type of myoepithelioma has close resemblance with plasmacytoid cells of PAs. Presence of non-cohesive epithelial clusters helps in differentiating PAs from myoepithelioma [9]. On FNAC of this breast tumor, the appearance of abundant myxoid matrix along with cell clusters composed of monotonous cellular population can be mistaken for matrix producing metaplastic carcinoma and mucinous carcinoma.
Metachromasia seen on Giemsa stain strongly suggest stromal mucin rather than mucin secreted by epithelial cells in case of mucinous carcinoma of breast. So Giemsa stain can be helpful in differentiating this benign tumor from mucinous carcinoma [10]. Histologically, adenomyoepithelioma lacks chondromyxoid stroma. Metaplastic carcinomas are characterized by infiltrating carcinoma admixed with malignant mesenchymal component. Phyllodes tumor lack myoepithelial component in the form of fine reticular pattern or sheets of spindle shaped or plasmacytoid cells [11]. Inadequate surgery of this PA, which is notorious for its pseudopod like extension into adjacent tissue, can results in recurrence [3].
Thus FNA done with adequate sampling from subareolar region can help in proper planning and management of PA and prevent unnecessary mastectomy.