Mucinous and secretory carcinomas of the breast are uncommon and indolent tumors.[7
] A conservative surgical approach for treatment is advocated because of their better prognosis. Morphological identification on FNAC is an important step in the workup.
In this study, we quantified the secretions in aspirates from breast carcinomas on a 3-point scale as minimal, moderate and extensive. Both mucinous and secretory carcinomas had extensive secretions. As noted by others, while these were extracellular in mucinous carcinomas,[1
] secretory carcinomas were characterized by predominantly intracellular secretions.[3
] Thus, quantifying the secretions and characterizing their location appears to be useful in separating these two lesions.
Extracellular secretions have been described in mucinous carcinoma and some IDC.[2
] Mucinous carcinoma is characterized by poorly cellular, abundant mucoid aspirate, extensive extracellular secretion, thin-walled vessels and few single and small clusters of cells floating in the secretions.[1
] We observed that the cell clusters comprised uniform cells with rounded contours reminiscent of those seen in tissue sections. Conversely, IDC with extracellular secretions, often mistaken for mucinous carcinoma,[2
] showed at least some cell clusters with irregular margins as in conventional IDC. Besides, the secretions in IDC were minimal to moderate compared to extensive in mucinous carcinoma. High nuclear grade in IDC with extracellular mucin has been used to differentiate mixed IDC and mucinous carcinoma.[2
] We propose that a careful search for the characteristic irregular margins of cell clusters is necessary and should be used as an additional distinguishing feature of IDC.
Mucocoele-like tumors need to be distinguished from mucinous carcinoma; however, being benign lesions, these are outside the scope of this study. In the literature, they are described as being characterized by an abundance of mucin and poor cellularity; the cells are present as monolayered sheets of epithelial cells.[1
Intracellular secretions have been described in secretory carcinoma,[3
] lobular carcinoma[5
] and some IDC. Though the morphological features on histopathology suggest that the secretions in secretory carcinoma are extensive in both extracellular and intracellular locations,[7
] in cytopathology smears there are predominantly intracellular secretions with minimal mucoid material in proximity to epithelial cells, and mucous globular structures.[3
] As visualized by transmission electron microscopy,[19
] the secretions are intracellular, within intracytoplasmic lumens, or present in extracellular lumens which are several times larger than the intracellular lumens. The latter are probably the mucous globular structures seen in cytology smears. In both our patients with secretory carcinoma, we observed small cellular clusters and single cells appearing to be strung on capillaries, probably caused by disintegration of papillary structures while smearing.
Intracytoplasmic lumens have also been described in lobular carcinoma and IDC.[20
] We did not encounter a single case of lobular carcinoma. Poor cellular yield, small hyperchromatic nuclei and nuclear molding have been described to characterize lobular carcinoma.[5
] In contrast, IDC are cellular, with high nuclear grade (nuclear enlargement and pleomorphism), and distinct cytoplasm.[5
None of our cases of mucinous and secretory carcinomas had necrosis. However, necrosis was encountered in four cases of high-grade ductal carcinomas with secretions. These observations are not unexpected as mucinous and secretory carcinomas are low-grade tumors.
To conclude, secretions are seen in a range of breast cancer that includes invasive ductal carcinoma, mucinous carcinoma and secretory carcinoma. Evaluation of the quantity and location of secretions and the contours of the cell clusters complement cell morphology, and could improve diagnostic cytopathological criteria. Small cellular clusters and single cells appearing to be strung on capillaries should be considered additional distinguishing features of secretory carcinoma.