Reporting Pancreatic FNAC using the Papanicolaou System: Still a Diagnostic Challenge

Abstract

Introduction: The Papanicolaou Society of Cytopathology System for reporting Pancreaticobiliary Cytology (PSCPC) is a reliable method to classify pancreatic fine needle aspiration cytology (FNAC) smears. However, it is not without practical problems which can diminish the diagnostic accuracy of the cytological diagnosis.

Aims and objectives: To determine the diagnostic pitfalls while reporting cytomorphology of pancreatic lesions according to PSCPC on correlating FNAC findings with histopathology.

Materials and methods: Retrospective analysis of pancreatic FNAC smears received in the Department of Pathology of our tertiary care institute over a period of 2 years was done. The cytological diagnoses were classified according to the Papanicolaou Society of Cytopathology system of reporting pancreaticobiliary cytology and correlated with histopathology. The reasons of cyto-histological discordance were analyzed.

Results: Out of 50 cases in which both FNAC and biopsy of pancreatic lesions were done, 34 cases were positive/malignant (Category VI), eight cases were suspicious for malignancy (Category V), three cases were neoplastic (Category IV), two cases were atypical (Category III), two cases were negative for malignancy (Category II), and one case was non-diagnostic (Category I). Out of 50 cases, histopathology was non-diagnostic due to inadequate material in six cases. The cytological diagnoses were compared with histopathology in the remaining 44 cases. Categories III, IV V, and VI were considered as positive for neoplastic pathology. The sensitivity of FNAC to predict neoplastic pathology was 97.5%, while the specificity was 25%. The positive predictive value was 92.9%. Two cases reported as atypical (Category III) turned out to be adenocarcinoma on histopathology. One case reported as neuroendocrine tumor and two cases reported as adenocarcinoma on cytology displayed features of chronic pancreatitis on histology. One case reported as neoplastic mucinous cyst (Category IV) turned out to be adenocarcinoma on histology (limited concordance).

Conclusion: The cytopathologist needs to be wary of the potential pitfalls to improve the diagnostic accuracy of FNACs.

Keywords: FNAC; Papanicolaou; malignant; neoplastic; pancreatic.

Figure 1

Discordant cases – a) Case reported Category IV- Neoplastic, Neuroendocrine tumor – small to medium sized cells having salt and pepper chromatin (PAP 400x); b) H and E section showing only acini with areas of fibrosis and lymphocytes – chronic pancreatitis (100x); c) Cytology reported as Category IV- Neoplastic - Solid pseudopapillary neoplasm. Photomicrograph shows a papillaroid cluster with cells lying away from fibrovascular core-. (PAP 400x); d) H and E section showing tumor cells having monomorphic nuclei with salt and pepper chromatin, arranged in cords, rosettes, and nests – proven on IHC as pancreatic neuroendocrine tumor (100x); e) Category VI- Positive or Malignant on cytology. Giemsa stain showing clusters of atypical cells (400x); f) H and E section showing distorted ducts with reactive atypia of lining epithelium and periductal chronic inflammation – chronic pancreatitis (400x)

Figure 2

Concordant cases- a) Category VI- Positive or Malignant – H and E smear showing a cohesive cluster of atypical cells exhibiting marked anisonucleosis (4:1) with irregular nuclear contours -Adenocarcinoma (400x) b) H and E section of trucut biopsy pancreas showing tumor arranged in glandular configuration extracellular mucin- Adenocarcinoma. (400x); c) Category VI- Positive or Malignant. Papanicolaou stain showing singly scattered medium-sized atypical lymphoid cells having high N/C ratio, fine chromatin, and scant cytoplasm- Lymphoma (400x); d) H and E section showing sheets of atypical lymphoid cells having vesicular nuclei, coarse nuclear chromatin, and scanty cytoplasm along with brisk atypical mitosis. (400x) Inset showing membranous positivity for c myc on IHC - Burkitt’s Lymphoma