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The PSC has developed a set of guidelines for the terminology and nomenclature of pancreatobiliary disease [28]. The proposed terminology recommends a six-tiered system comprising non-diagnostic, negative, atypical, neoplastic (benign and other), suspicious, and positive (Table 3).

Non-diagnostic specimens are those that provide no diagnostic or useful information. This may be due to technical or sampling issues. Absence of epithelial cells should not be presumed to be non-diagnostic as sampling from pancreatic pseudocysts and mucinous cysts can be acellular. Clinical and radiographic information is helpful in these instances. In the presence of any cellular atypia, the non-diagnostic category should not be used. Cytological interpretation can be limited by the amount of material aspirated or by preparation artifact such as tissue entrapped in a blood clot precluding cytological evaluation. The presence of only gastrointestinal contaminants or normal pancreatic tissue in the context of a well-defined pancreatic mass are some examples that should be included in this category.

A negative cytology is a sample that contains adequate tissue to define a lesion that is identified on radiology. It may indicate benign entities like acute, chronic, and autoimmune pancreatitis, pseudocyst, ectopic, and intrapancreatic splenule and lymphoepithelial cyst.

Atypical categories include cases with features that are more than reactive changes, low cellularity, premalignant (dysplastic) changes, and cases assigned due to observer caution. The cytological specimen may contain cells with morphological features beyond recognizable normal or reactive changes. An atypical diagnosis raises the possibility of a neoplasm, especially a low-grade neoplasm. The “neoplastic” category is separated into “benign,” which includes neoplasms such as serous cystadenoma, and “other,” which includes premalignant lesions such as mucinous cysts, IPMN, and low-grade malignant tumors such as PanNETs and SPN.

The PSC guidelines use the term “suspicious for malignancy” to cover a range of atypias falling just short of that necessary for a definitive diagnosis of malignancy. These specimens lack sufficient diagnostic features for a definitive diagnosis. Other information, such as clinical, imaging, or ancillary test findings, must be correlated with the cytologic findings before surgical intervention can be undertaken.

The positive category includes malignant neoplasms such as PDAC, ACC, poorly differentiated neuroendocrine carcinomas, pancreatoblastoma, lymphoma, and metastases. This category is used when unequivocal features of malignancy are identified.

Table 3. Standardized terminology for pancreatic cytology by the PSC