DIAGNOSTIC VALUE OF A SENSITIVE NEXT GENERATION SEQUENCING PANEL WITH UNIQUE MOLECULAR IDENTIFIERS (UMIS) FOR EVALUATING ROUTINE EUS-FNA SMEARS OF SOLID PANCREATIC LESIONS

Aims Detection of clonal mutations may be of additional value for EUS-guided FNA. The amount of tissue on smears is often limited. Standard targeted next generation sequencing (NGS) approaches lack sensitivity to detect mutations in little material. The aim of this study was to investigate the diagnostic value of a NGS panel with unique molecular identifiers (UMI-NGS) on smears from solid pancreatic lesions with various cytological gradings according to the Bethesda criteria.

Methods Forty EUS-FNA single slide smears of solid pancreatic lesions were selected retrospectively covering the six categories of the standardized Bethesda terminology for pancreatobiliary cytology.

UMI-NGS analysis (ThermoFisher, Oncomine Colon cfDNA Assay) was performed on all samples. The results of both cytology and NGS analyses were compared with the definite diagnosis after surgery or at least one year of follow-up.

Results The cytological diagnosis was correct, compared to the follow-up, in 63% of the cases. NGS analysis was performed successfully in 83% of the cases based on one smear slide with a UMI-NGS panel. UMI-NGS altered the morphological diagnosis (b5 to b6) in 2 out of 33 cases (6%). For the morphological diagnoses non-diagnostic, benign and atypical, UMI-NGS did not lead to additional malignant diagnosis whereas>50% of these cases proved malignant during follow-up ([Tabel. 1]).

Table 1

Morphology	Non-diagnostic	Benign	Atypical
Number of cases	3	7	3
UMI-NGS panel result	2 insufficient material	3 insufficient material	2 insufficient material
	1 no mutations found	3 no mutations found	1 no mutations found
		1 KRAS mutation only
Follow-up	2 malignant	4 malignant	3 malignant
	1 benign	3 benign

Conclusions In this pilot study UMI-NGS analysis was of limited additional value to the morphological evaluation of a single FNA smear. Non-diagnostic FNA smears all remained non-diagnostic after NGS. Results of UMI-NGS analysis can be helpful in diagnosing pancreatic malignancies when the pathologist is doubtful.

Publication History

Article published online:
14 April 2022