Pancreatoblastoma: Cytologic and histologic analysis of 12 adult cases reveals helpful criteria in their diagnosis and distinction from common mimics

• Authors: Michelle Reid, Emory University; Shristi Bhattarai, Georgia State University; Rondell P. Graham, Mayo Clinic; Burcin Pehlivanoglu, Emory University; Carlie S. Sigel, Memorial Sloan Kettering Cancer Center; Jiaqi Shi, University of Michigan; Anjali Saqi, Columbia University; Maryam Shirazi, Columbia University; Yue Xue, Emory University; Olca Basturk, Memorial Sloan Kettering Cancer Center; Nazmi Adsay, Emory University
• Journal Title: Cancer Cythopathology
• Volume: Volume 127, Number 11
• Publisher: Wiley | 2019-10-03, Pages 708-719
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1002/cncy.22187
• Subjects: Health Sciences, Oncology; Health Sciences, Pathology; Biology, Cell
• Keywords: Science & Technology; Life Sciences & Biomedicine; Oncology; Pathology; cytology; fine-needle aspiration (FNA); pancreas; pancreatoblastoma; Needle aspiration cytology; Neoplasms; Carcinoma; Pancreas; Catenin; Infant

Abstract

BACKGROUND: Pancreatoblastoma (PBL) is a rare malignant pancreatic tumor seen predominantly in childhood, and its cytologic diagnosis remains challenging. METHODS: Twelve fine-needle-aspirations from 11 adults were analyzed. RESULTS: In total, 6 men and 5 women (median age, 45 years; age range, 32–60 years) had tumors measuring a median 5.6 cm (range, 2.5–12 cm) located in the pancreatic head (n = 7) or tail (n = 4), including 3 with familial adenomatous polyposis (FAP)/FAP-related syndromes and 4 with metastasis at diagnosis. The median follow-up was 39.8 months (range, 0.8–348 months), and 5 patients died of disease. The original cytology diagnoses were: PBL (n = 2), neuroendocrine neoplasm (n = 2), poorly differentiated neuroendocrine carcinoma (n = 2), well differentiated neuroendocrine tumor (n = 1), poorly differentiated carcinoma (n = 2), “positive for malignancy” (n = 1), acinar cell carcinoma (n = 1), and epithelioid neoplasm with endocrine and acinar differentiation versus PBL (n = 1). Universal cytopathologic findings included hypercellularity; 3-dimensional clusters; and single, monotonous, blast-like cells that were from 1.5 to 2.0 times the size of red blood cells with high nuclear-to-cytoplasmic ratio, fine chromatin, small, distinct nucleoli, and a resemblance to well differentiated neuroendocrine tumor and poorly differentiated neuroendocrine carcinoma. Branching pseudopapillae (n = 7) and grooved nuclei (n = 3) raised the differential diagnosis of solid-pseudopapillary neoplasm, but with more atypia. Uncommon features included pleomorphism (n = 4) and numerous mitoses (n = 1). Squamoid morules were seen on smears (n = 5) or cell blocks (n = 6) in 70% of patients and were characterized by epithelioid cells with elongated, streaming nuclei, fine chromatin, absent nucleoli, and positive nuclear β-catenin (n = 6 of 8). The median Ki-67 index was 21% (range, 2%−70%), and neuroendocrine marker expression was common (100%), but acinar markers were variable (63%). CONCLUSIONS: A combination of cytologic findings in PBL, including a predominant population of primitive blast-like cells, subtle squamoid morules, frequent neuroendocrine and variable acinar phenotype, should facilitate accurate cytologic diagnosis and distinction from common mimics.