Cytology has a key role in the step-wise diagnostic approach to pancreatic mass lesions. Brush cytology and ultrasound-guided endoscopic fine-needle aspiration provide specimens for diagnosis prior to surgical or conservative therapy. The diagnostic system of the Papanicolaou Society of Cytopathology provides a conceptual framework for reporting these specimens. Cystic lesions represent a particular challenge in pancreatic cytology, as in many instances a purely morphological approach will not result in an adequate diagnostic interpretation. Noteworthy from a conceptual point of view is how the Papanicolaou Society System incorporates non-morphological methods: laboratory chemical (CEA >192 ng/ml) and molecular (KRAS and/or GNAS mutations) findings are part of the formal diagnostic criteria for neoplastic cysts.
The Bern experience shows that such an integrated approach results in a significantly increased diagnostic yield. Among 83 samples analyzed, adequate DNA could be extracted in 79 samples (95%). Next generation sequencing identified pathogenic mutations in 46 cases (58%). Of these, in 35 (76%) a neoplastic cyst could not have been diagnosed by morphology alone.
These findings illustrate a new perspective for diagnostic situations, where morphology alone does allow for a sufficient diagnostic work-up. Along this line of thinking, liquid biopsy should not be regarded as a replacement, but rather an extension of the cytology's diagnostic armamentarium, according to the principle of "doing more with less."