Nodular Histiocytic Aggregates of the Greater Omentum Mimicking Peritoneal Carcinomatosis on Imaging

Nodular histiocytic/mesothelial hyperplasia (NHMH) is a benign reactive process characterized by the proliferation of histiocytic cells and scattered mesothelial cells. We report a case of NHMH of the greater omentum in a 56-year-old HIV-positive male who presented with paraumbilical swelling and multiple omental nodules on imaging. The preoperative assessment of the patient reveals an inverted CD4/CD8 ratio. The patient underwent herniorrhaphy and an excisional biopsy of the greater omentum. Pathological examination reveals mesothelial-lined fibroadipose tissue containing nodular aggregates of histiocytic cells, with immunohistochemical staining for CD68 and CK7 confirming the histiocytic and mesothelial nature of the lesional cells, respectively. The patient received antiretroviral therapy and antibiotics and was discharged in good condition. This is the first case report presenting the occurrence of NHMH in an HIV-positive patient. Although it is a benign lesion, it can mimic malignancy on imaging. The diagnosis was made based on histopathological examination along with immunohistochemical staining. In our case report, NHMH presents with diffuse infiltration of the greater omentum on imaging. This emphasizes the importance of recognizing this pathological entity along with clinicopathological correlation to avoid misdiagnosis that may adversely affect patient outcomes.