A Rare Case of Iliopsoas Muscle and Retroperitoneal Lesion Secondary to Malakoplakia.

Malakoplakia is a rare, benign granulomatous inflammatory disorder caused by a defect in the phagolysosomal function of macrophages, which often mimics neoplastic or severe infectious processes. We present a case of a 43-year-old immunocompetent woman with abdominal and right inguinal pain, in whom imaging studies identified a solid retroperitoneal pelvic mass and focal involvement of the right iliopsoas muscle, highly suggestive of metastatic malignancy. Initial and definitive histopathological examination following laparoscopic resection confirmed the diagnosis by demonstrating infiltration by foamy macrophages (von Hansemann cells) with pathognomonic basophilic intracytoplasmic inclusions (Michaelis-Gutmann bodies) and positive CD68 staining. The patient had a favorable clinical course following surgical intervention and prolonged antibiotic therapy with agents exhibiting high intracellular penetration. Retroperitoneal and iliopsoas involvement in immunocompetent patients represents an exceedingly rare presentation. Timely histopathological diagnosis is essential to guide multidisciplinary management and rule out malignancy.