Gonadal MRI in Complete Androgen Insensitivity Syndrome: Pathologic Correlation and Low-Risk Features.

CONTEXT: In complete androgen insensitivity syndrome (CAIS), gonadectomy is increasingly deferred until after puberty, creating a need for imaging-based strategies that distinguish low-risk gonads from those warranting surgical intervention. OBJECTIVE: To define multiparametric MRI features associated with absence of clinically relevant macroscopic gonadal neoplasia in postpubertal individuals with molecularly confirmed CAIS. METHODS: We retrospectively evaluated 32 gonads from 16 postpubertal individuals with molecularly confirmed CAIS who underwent preoperative pelvic MRI, including diffusion-weighted imaging, followed by bilateral gonadectomy. MRI findings were reviewed by expert radiologists and correlated with gonadal volume and histopathologic assessment. RESULTS: Macroscopic neoplasia was identified in three patients and included seminoma with adjacent germ cell neoplasia in situ, a large-cell calcifying Sertoli cell tumor, and a serous borderline tumor of Müllerian type. Homogeneous MRI signal and absence of diffusion restriction were each associated with absence of macroscopic neoplasia and yielded a negative predictive value of 100% in this cohort. Gonadal volume also separated benign from neoplastic lesions: all non-neoplastic gonads measured ≤21.9 cm3, whereas all neoplastic lesions measured ≥116.4 cm3. False-positive diffusion restriction occurred only in small gonads and corresponded histologically to Leydig cell hyperplasia. CONCLUSION: In postpubertal CAIS, homogeneous signal, absence of diffusion restriction, and low gonadal volume may identify gonads at low risk for macroscopic neoplasia and support conservative surveillance in selected individuals. Diffusion-weighted imaging on MRI should be interpreted cautiously, particularly in small gonads, where Leydig cell hyperplasia may mimic neoplasia.