Invasive micropapillary carcinoma of the male breast masked by bilateral gynecomastia: a multimodality imaging case report

Abstract Background Male breast lesions are uncommon and may present diagnostic challenges, particularly in the setting of concomitant gynecomastia, which can obscure or mimic underlying pathology. Multimodality imaging plays a key role in lesion detection and characterization. Case presentation We report the case of a 60-year-old man presenting with bilateral breast enlargement. Ultrasound demonstrated typical features of gynecomastia in the left breast, characterized by retroareolar glandular proliferation with a dendritic pattern. In the right breast, a hypoechoic solid mass measuring 11 × 19 mm was identified in the peri-areolar region of the upper inner quadrant, with irregular and lobulated margins, and was classified as BI-RADS 4. Color Doppler revealed mild intralesional vascularity. Breast MRI demonstrated a corresponding lesion with heterogeneous intermediate signal intensity on T2-weighted SPAIR images, intermediate signal intensity on T1-weighted images, and early heterogeneous contrast enhancement. Dynamic contrast-enhanced imaging showed a type III kinetic curve. Diffusion-weighted imaging demonstrated high signal intensity of the lesion. On contrast-enhanced thoraco-abdomino-pelvic CT, the lesion was poorly conspicuous and only retrospectively identified, whereas bilateral gynecomastia was noted. Core needle biopsy established malignancy preoperatively. Final pathology after bilateral mastectomy revealed a 2-cm invasive micropapillary carcinoma of the right breast with equivocal HER2 expression (immunohistochemical score 2 +), while the left breast showed gynecomastia without evidence of malignancy. Conclusions This case highlights the diagnostic value of multimodality imaging in male breast lesions, especially in the presence of gynecomastia. Ultrasound remains essential for lesion detection and characterization, while MRI provides valuable complementary information. CT may fail to depict small breast lesions, emphasizing the importance of dedicated breast imaging and radiologic–pathologic correlation.