What is a neuroma, particularly in a patient with a history of recent right lower lobe segmentectomy (surgical removal of a lung segment) and persistent postoperative pain?

What is a Neuroma?

A neuroma is a benign, non-neoplastic proliferative mass of disorganized nerve tissue that forms after peripheral nerve injury, commonly occurring following trauma, surgery, or amputation, and can cause debilitating neuropathic pain. 1, 2

Pathophysiology and Formation

• Neuromas develop when axons from the proximal nerve stump attempt to regenerate after nerve transection or partial disruption but grow in a disorganized manner, becoming embedded in connective tissue and scar 1, 3
• The regenerative process involves inflammation and collagen remodeling that creates a bulbous mass at the injury site, which is why they are also called "traumatic neuromas," "amputation neuromas," or "stump neuromas" 1, 3
• In neuroma-in-continuity lesions, internal neuronal elements are partially disrupted with variable damage to endoneurium and perineurium, while the epineurium typically remains intact 4

Clinical Context: Post-Thoracic Surgery

In patients with persistent pain after right lower lobe segmentectomy, neuromas can form from intercostal nerve injury during surgical dissection or rib retraction. 5

• Post-thoracotomy pain syndrome is a recognized complication where nerve injury during chest wall manipulation leads to neuroma formation 5
• The intercostal nerves are particularly vulnerable during thoracic procedures, and resulting neuromas can cause chronic neuropathic pain in the surgical distribution 5, 2

Diagnostic Criteria

To diagnose symptomatic neuroma, patients must meet specific criteria based on history, examination, and confirmatory testing. 6

Required Criteria (All 3 Must Be Present):

• Pain with at least 3 neuropathic characteristics (burning, stabbing, electric-shock-like, shooting, or lancinating quality) 6
• Symptoms in a defined neural anatomic distribution corresponding to the injured nerve 6
• History of documented or suspected nerve injury (surgical, traumatic, or chronic compression) 6

Confirmatory Findings (At Least 2 of 4 Required):

• Positive Tinel sign on examination at or along the suspected nerve injury site 6
• Focal tenderness or pain on palpation at the suspected injury location 6
• Positive response to diagnostic local anesthetic nerve block 6
• Ultrasound or MRI confirmation showing a focal nerve mass 1, 6

Imaging Characteristics

• Ultrasound is the first-line imaging modality, showing a hypoechoic or mixed-echogenicity mass in continuity with or at the end of a nerve 1
• MRI provides superior soft tissue characterization and can differentiate neuromas from true nerve sheath tumors or local tumor recurrence in oncologic patients 1
• The combination of US and MRI allows safe characterization of neurogenic lesions with significant impact on treatment planning 1

Common Pitfalls in Post-Surgical Patients

In oncologic patients with prior surgery, neuromas can mimic local tumor recurrence, making imaging differentiation critical. 1

• Neuromas appear as focal masses along the nerve distribution and may enhance on MRI, potentially causing diagnostic confusion with recurrent malignancy 1
• The key distinguishing feature is the neuroma's direct continuity with an identifiable nerve and history of surgical nerve manipulation 1
• Electrodiagnostic testing showing denervation in the distribution of the affected nerve supports neuroma diagnosis over tumor recurrence 4

Clinical Significance

• Symptomatic neuromas cause substantial morbidity through both neuropathic pain and functional deficits from the underlying nerve injury 2
• The pain is often described as constant burning or intermittent shooting sensations, with hypersensitivity to touch or pressure over the neuroma site 2, 6
• Cold intolerance is a common associated symptom that helps distinguish neuroma pain from other post-surgical pain syndromes 6