How should I evaluate and manage an adult with an unexplained fibroinflammatory mass?

Evaluation and Management of Fibroinflammatory Masses in Adults

Initial Risk Stratification

Any adult presenting with an unexplained fibroinflammatory mass requires urgent evaluation to exclude malignancy, as these lesions clinically and radiologically mimic malignant neoplasms and cannot be reliably distinguished without tissue diagnosis. 1, 2, 3

High-Risk Features Requiring Immediate Work-Up

• Duration ≥ 2 weeks without significant fluctuation mandates urgent malignancy evaluation 1, 4
• Size > 1.5 cm in greatest dimension 1, 4
• Firm or hard consistency on palpation 1, 4
• Fixation to adjacent structures suggesting capsular invasion 1, 4
• Absence of infectious signs (no fever, erythema, warmth, rapid onset, recent URI, or dental problems) 1, 4

Diagnostic Algorithm

Step 1: Contrast-Enhanced Cross-Sectional Imaging

Obtain CT with IV contrast (or MRI with contrast if CT contraindicated) immediately for any mass meeting high-risk criteria. 1, 4, 5

• CT provides superior characterization of mass architecture, relationship to adjacent structures, and presence of concerning features like rim enhancement or central necrosis 5
• MRI is particularly useful for deep-seated lesions and provides better soft tissue characterization 1, 5
• Do not proceed to tissue sampling without imaging first, as cross-sectional imaging guides subsequent biopsy approach and surgical planning 5

Step 2: Targeted Physical Examination

Perform or refer for visualization of the larynx, base of tongue, and pharynx to exclude occult primary malignancy before any tissue sampling. 1, 4

• This is critical because fibroinflammatory masses can represent metastatic disease, particularly cystic metastases from oropharyngeal primaries 1, 5
• In patients over 40 years, cystic neck masses carry an 80% malignancy rate 5

Step 3: Tissue Diagnosis

Fine-needle aspiration (FNA) is the preferred initial tissue sampling method, offering 94-96% diagnostic accuracy. 1, 4

• Perform FNA under ultrasound guidance to maximize yield 1, 4
• If initial FNA is nondiagnostic, repeat under image guidance before considering open biopsy 1, 4
• For suspected lymphoma, core-needle biopsy provides superior sensitivity (92% vs 74% for FNA) 4
• Never perform open surgical biopsy before completing imaging, FNA, and endoscopic evaluation, as this impairs staging and treatment 1, 4, 5

Step 4: Examination Under Anesthesia (If Diagnosis Remains Uncertain)

If malignancy cannot be excluded after imaging and FNA, perform examination of the upper aerodigestive tract under anesthesia before any open biopsy. 1, 4

• This helps locate occult primary sites and prevents compromising subsequent cancer treatment 4

Specific Considerations for Fibroinflammatory Lesions

Inflammatory Myofibroblastic Tumor (IMT)

• IMTs are locally aggressive neoplasms that can occur in soft tissue, viscera, head and neck, and mesentery 1, 6, 7
• On imaging, IMTs appear as homogeneous or heterogeneous masses with variable enhancement on delayed CT/MRI acquisitions due to fibrosis 7
• T1 and T2-weighted MRI typically shows low signal intensity reflecting fibrotic tissue 7
• ALK fusions occur in 50-60% of IMTs, with response rates >80% to crizotinib in ALK-positive cases 1
• NTRK fusions occur rarely in ALK-negative IMTs and may respond to TRK inhibitors 1
• Complete surgical resection is curative but local recurrence occurs in 25% of pediatric cases 1

Tumefactive Fibroinflammatory Lesion (TFIL)

• TFIL is a rare idiopathic fibrosclerosing disorder that clinically mimics malignancy or infection 2, 3
• These lesions are histologically benign but present as tumor-forming masses 3
• Repeated biopsies may be necessary to establish diagnosis, as initial biopsies are often non-revealing 2
• Corticosteroid therapy produces prompt response once diagnosis is confirmed 2

Mesenteric Fibromatosis

• Locally aggressive benign proliferative process that may occur sporadically or with familial adenomatous polyposis 6
• Manifests as focal mesenteric mass simulating lymphoma, metastatic disease, or soft-tissue sarcoma 6

Retroperitoneal Fibrosis

• FDG-PET/CT is useful for assessing disease activity, particularly in asymptomatic patients with elevated acute phase reactants 1
• Abnormal FDG uptake in retroperitoneal tissue involving the abdominal aorta indicates active inflammation 1

Critical Pitfalls to Avoid

• Never assume a cystic-appearing mass is benign without definitive diagnosis, as malignancies (papillary thyroid carcinoma, lymphoma, oropharyngeal carcinoma) frequently present cystically 1, 4, 5
• Avoid empiric antibiotics unless clear bacterial infection signs are present (fever, warmth, erythema, rapid onset), as this delays malignancy diagnosis and promotes resistance 1, 4, 5
• Do not rely on imaging alone to exclude malignancy, as fibroinflammatory lesions radiologically mimic malignant neoplasms 2, 3, 7
• Partial resolution with antibiotics does not exclude malignancy, as infection may coexist with underlying malignancy 4

Follow-Up Protocol

• If a trial of antibiotics is given for suspected infection, re-evaluate within 2 weeks 4
• If the mass has not completely resolved, initiate full malignancy work-up immediately 4
• After complete resolution, follow-up at 2-4 weeks to monitor for recurrence 4
• For confirmed benign fibroinflammatory lesions, surveillance intervals depend on specific diagnosis and treatment response 2