I got some very good responses. This is an example of ACINIC CELL CARCINOMA (腺泡细胞癌) of the salivary gland.

Generally, FNA of the salivary gland is very accurate on diagnosing salivary gland neoplasm vs. non-neoplastic lesions and it is good at differentiating high-grade malignant neoplasm vs. low-grade malignant neoplasm. The difficult area is to differentiating a low-grade malignant neoplasm vs. a benign neoplasm. This case at low-power ilustrate a papillary structure (乳头状结构) and on the Diff-Quick stained sldes show some metachromatic matrix-like material, which can be mis-interpretated as the matrix in either benign mixed tumor or more likely a basal cell neoplasm. However, if you look carefully on high power of the Pap stained slide, the neoplastic cells are monotonous and have abundant granular cytoplasm and no significant atypia. The key is monotonous. I guess you can also think about Oncocytoma, but the papillary structure makes it unlikely. Remember, acinic cell carcinoma can be papillary. So, put everything together, the papillary structure with fibrovascular cores (those metachromatic material), the monotonous neoplastic cells with granular to somewhat clear cytoplasm, the clean background, acinic cell carcinoma is the most likely diagnosis. Another possibility is metastatic renal cell carcinoma (papillary renal cell carcinoma), which can look exactly like this. This patient did not have a kidney mass. The FNA cytology diagnosis was " Salivary gland neoplasm, favor acinic cell carcinoma". The surgical resection specimen proved that it is a papillary-cystic variant of acinic cell carcinoma.

Yes, to make a diagnosis on FNA cytology is important. But, sometimes, to get the patients to correct clinical management is more important than diagnosis itself. For most of the benign (except Warthin's tumor) and malignant primary salivary gland neoplasms, surgical resection is the treatment of choice, even it is benign mixed tumor. So, even if you don't know the exact answer, as long as you are sure that it is a salivary gland neoplasm, the surgeons will be happy. If you can provide more imformation regarding the malignancy of the tumor, that is certainly better.

I hope the discussion is helpful.

LC