FDG Avid Plugoma Mimicking Recurrent Lymphoma

CASE

Maximum intensity projection (MIP) image [Fig 1a] reveals focal 18F fluorodeoxyglucose (FDG) uptake in the pelvis (black arrow). Axial CT image [Fig 1b] shows a nodular heterogeneous soft tissue density in the right pelvis, at the surgical mesh site (white arrow), measuring about 3.0 cm. Fused axial positron emission tomography/computed tomography (PET/CT) image [Fig 1c] demonstrates 18F FDG uptake (SUV max of 3.5) corresponding to the CT abnormality (white arrow), suggestive of an inflammatory reaction at the site of the mesh plug, consistent with a plugoma. The focus of FDG uptake seen in the right inguinal canal, below the white arrow, was secondary to inflammation from recent surgery, the hernia repair.

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Fig 1:

(a) Whole body MIP image from FDG PET/CT showing focal uptake in the right side of the pelvis, adjacent to the urinary bladder (black arrow). (b) CT image from the PET/CT, at the level of the pelvis, showing a heterogenous 3.0 cm density (white arrow), mimicking an enlarged lymph node. (c) Fused PET/CT image at the level of the pelvis showing FDG uptake in the right pelvic density (white arrow), SUV measuring 3.5.

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Prosthetic mesh, commonly used in inguinal hernia repair, may trigger a chronic foreign body response resulting in a plugoma – a benign granulomatous pseudotumor caused by mesh-induced inflammation and fibrosis. Plugomas, also referred to as “meshoma” or “mesh-related inflammatory pseudotumor”, typically develop weeks to months following hernia repair with prosthetic materials. It represents a rare but increasingly recognized complication, characterized by granulomatous inflammation, fibrosis, and possible soft-tissue mass formation.^[1,2] On computed tomography scans, plugomas typically appear as a localized heterogeneous soft-tissue density at the mesh site. While benign, these masses demonstrate variable fluorodeoxyglucose (FDG) uptake, due to ongoing macrophage and fibroblast activity, and may mimic malignant pathology.^[2-5] In a study of 22 patients, the mean SUV max reported in postoperative FDG uptake was 4.0 ± 2.3.^[4] This uptake may persist for years after surgery, which is particularly problematic among cancer patients undergoing PET-CT surveillance.^[3,4,6-8] In HIV-positive patients with concurrent malignancies, immune system alterations further complicate postoperative monitoring, potentially affecting the development and imaging characteristics of postsurgical complications. Given these overlapping factors, radiologists must exercise caution when evaluating FDG-avid lesions in postoperative oncology patients.

Our case illustrates the diagnostic complexity of evaluating FDG-avid masses at postoperative surgical sites in oncology patients. The hypermetabolic activity of the postsurgical soft-tissue mass seen in our case was concerning for lymphoma recurrence. However, the lesion’s extranodal location at the herniorrhaphy site and the timing of its appearance (3 months postoperatively) favored a benign etiology. Postoperative plugoma should be considered in the differential diagnosis of FDG-avid masses at hernia repair sites in cancer patients undergoing surveillance imaging, including immunocompromised patients with a history of lymphoma. Lymphoma recurrence frequently involves nodal or visceral sites, whereas plugomas localize to surgical beds and should not demonstrate progression or spread.^[4,7-9] Awareness of surgical history, timing of mesh placement, and lesion location is critical for radiologists and clinicians to distinguish plugoma from malignancy and avoid unnecessary biopsies or treatment.