Abstract: SA-PO0960
Papillary Epithelial Proliferations in Inherited Cystic Kidney Diseases: A Clinicopathologic Consecutive Series Evaluation
Session Information
- Pathology: Updates and Insights
November 08, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Pathology and Lab Medicine
- 1800 Pathology and Lab Medicine
Authors
- Tanaka, Kara, University of California San Francisco, San Francisco, California, United States
- Wu, Douglas, Stanford University, Stanford, California, United States
- Williamson, Sean R, Cleveland Clinic, Cleveland, Ohio, United States
- Chan, Emily, Stanford University, Stanford, California, United States
- Sangoi, Ankur, Stanford University, Stanford, California, United States
Background
Small intracystic epithelial proliferations (hereafter referred to as “papillary epithelial proliferations” (PEP)) have been described in concert with other atypical renal cysts (ARC) or neoplastic renal lesions, however, complete clinicopathologic assessment and incidence of PEP in hereditary polycystic kidney disease is not yet known.
Methods
Consecutive nephrectomies for autosomal dominant (ADPKD) or autosomal recessive polycystic kidney disease (ARPKD) were reviewed for evaluation of PEP, defined as tufted or papillary intracystic growths covered by a single layer of cuboidal cells with minimal amphophilic cytoplasm and low-grade nuclei [Fig. 1]. Lesions with clear cells or multilayering were excluded. Features of PEP were recorded: number of cysts with PEP, size of most prominent PEP per case (height, width, size of cyst containing PEP), architecture, and cytology.
Results
49 nephrectomies (34 ADPKD, 15 ARPKD) from 29 patients (20 bilateral) demonstrated PEP in 60% (28/47) of kidneys, with higher incidence in ADPKD (84%, 27/32) vs ARPKD (7%, 1/15). Architectural patterns included tufted (97%), papillary (73%), hobnail (63%), micropapillary (63%), and hierarchical branching (10%). Amphophilic (97%) and eosinophilic cytoplasm (37%) were seen. The most well-developed PEP per case measured on average 0.3 x 2.1 mm (height x width) and were present in cysts averaging 3 mm in diameter.
Conclusion
PEP are common microscopic findings in nephrectomies from patients with ADPKD and, less frequently, ARPKD. While a subset of kidneys with PEP also showed neoplastic lesions (2/29, 7%) or ARC, we hypothesize that PEP are likely reactive rather than neoplastic. Immunohistochemical and molecular characterization is ongoing to further evaluate PEP.