Atraumatic Breast Fat Necrosis Mimicking Malignancy in End-Stage Renal Disease: A Case Report.

BACKGROUND Breast fat necrosis is a benign process in which fat undergoes aseptic saponification by blood and tissue lipase. It commonly occurs due to trauma or surgery and can mimic malignancy. We present an unusual case of atraumatic fat necrosis caused by extensive breast arterial calcifications in a woman with underlying diabetes mellitus and end-stage renal disease (ESRD). CASE REPORT A 61-year-old woman presented with a painful left breast lump for 3 days. Her medical history included hemodialysis-dependent ESRD, diabetic nephropathy, and poorly controlled tertiary hyperparathyroidism. Initial mammography revealed extensive arterial wall calcifications with no discrete mass, while ultrasound showed a poorly defined heterogeneous, predominantly hyperechoic mass. The lesion enlarged over 5 months, prompting surgical excision. Histopathological examination revealed extensive fat necrosis and widespread vascular calcification affecting variably sized vessels in a Mönckeberg sclerosis-like pattern. The calcification was severe enough to cause focal complete vascular occlusion with resultant infarction of breast fat. CONCLUSIONS This case highlights a rare and unusual presentation of atraumatic fat necrosis of the breast mimicking breast malignancy, both clinically and radiologically. Unlike the more common post-traumatic or post-surgical fat necrosis, this instance occurred in the absence of any known injury or intervention, making the diagnosis more challenging. It underscores the importance of considering fat necrosis in the differential diagnosis of breast masses in patients with ESRD, who often exhibit severe calcific vasculopathy, which can lead to tissue ischemia. Awareness of this potential mimic will be helpful in avoiding unnecessary interventions and guiding appropriate management.