Pseudopapillary and micropapillary-like changes in classical renal angiomyolipoma: a multi-institutional series of 60...

Area of Science:

• Uropathology
• Oncologic Pathology
• Renal Neoplasms

Background:

• Classical renal angiomyolipoma (AML) can exhibit pseudopapillary- and micropapillary-like morphologic patterns.
• These patterns may lead to diagnostic confusion with renal cell carcinoma or urothelial carcinoma.
• The incidence and clinical significance of these less-recognized AML morphologies require further investigation.

Purpose of the Study:

• To evaluate the incidence of pseudopapillary- and micropapillary-like changes in a multi-institutional cohort of classical renal angiomyolipoma (AML).
• To determine the association of these morphologic patterns with clinicopathologic features, particularly fat content.
• To emphasize the importance of recognizing these features for accurate diagnosis and to avoid misdiagnosis.

Main Methods:

• Retrospective analysis of a multi-institutional cohort of 60 patients diagnosed with classical AML.
• Genitourinary pathologists reviewed cases, recording tumor characteristics including fat assessment and the extent of pseudopapillary/micropapillary-like changes.
• Chi-square tests were used to assess associations between morphologic patterns and tumor subtype.

Main Results:

• Pseudopapillary/micropapillary changes were identified in 19 out of 60 cases (32%).
• These changes were significantly more frequent in fat-poor AML (57%) compared to non-fat-poor AML (7%; p < 0.001).
• No recurrences or tumor-related deaths were observed during a median follow-up of 11 months.

Conclusions:

• Pseudopapillary- and micropapillary-like changes are underappreciated morphologic patterns in classical renal angiomyolipoma (AML).
• These features occur significantly more often in fat-poor AML, a critical distinction for diagnosis.
• Recognition of these patterns, especially in biopsy specimens, is crucial to prevent misdiagnosis as other renal malignancies.