Painful lateral node biopsy: Traumatic neuromas after neck surgery

Issue: October 2012

ByStephanie L. Lee, MD, PhD, ECNU

A 42-year-old female with papillary thyroid cancer with a moderate risk for recurrence presented to the endocrine clinic. She was AJCC stage 1 and her ATA risk was moderate.

When the patient was aged 30 years, a left lobectomy for a thyroid mass showed a well differentiated papillary thyroid cancer (PTC) with extensive lymphovascular and extrathyroidal extension and two metastatic nodes in the paratracheal (level 6) and the left lateral neck (level 2).

Completion thyroidectomy was postponed because of pregnancy. Levothyroxine was started for thyroid-stimulating hormone suppression, but her dose was sequentially reduced and finally stopped because of hyperthyroidism. Two years after her initial surgery, a diagnostic radioactive iodine (RAI) uptake scan showed diffuse right lobe uptake without cold nodule and no extrathyroidal uptake.

Stephanie Lee

The scan and elevated 24-hour uptake of 71% was consistent with Graves’ disease.

The patient refused completion thyroidectomy and she was treated with 15.8 mCi I-131. Six months later, a recombinant human (rhTSH)-stimulated RAI I-123 whole-body scan showed ablation of the thyroid and no metastatic disease.

The patient was lost to follow-up and returned 6 years later.

A simultaneous rhTSH-stimulated RAI whole-body scan and F18-fluorodeoxyglucose (FDG) PET scan showed bilateral iodine non-avid hypermetabolic level 2 nodes. Without biopsy, she had a bilateral level 2 compartment dissection showing benign right level 2 nodes and a traumatic neuroma in left level 2. No metastatic disease was found.

Figure 1. F18-FDG-PET scan. Axial view of the level 2, submandibular area of the cervical neck. The very hypermetabolic node (yellow) was a benign reactive node on cytology with a thyroglobulin on the needle wash of <0.2 ng/mL. The remainder of the isotope seen was physiological excretion in the oropharynx.

Reprinted with permission from: Stephanie L. Lee, MD, PhD

Two years later, she transferred to my care, and repeat rhTSH-stimulated PET/CT scan showed a new left level 2 node with significantly increased metabolic activity, SUV 5.6 (Figure 1). Her current thyroglobulin antibody level had fallen from the initial value of 44 U/mL (normal <20 U/mL) but remained elevated at about 23 U/mL. Because of the interference with the thyroglobulin immunometric assay causing a false-negative result, a thyroglobulin by radioimmunoassay was performed showing a thyroglobulin of 0.9 ng/mL and a thyroglobulin antibody 1.6 U/mL (normal <0.4 U/mL).

Ultrasound in my clinic showed the PET scan positive node corresponded with a morphologically enlarged node measuring 2.8 (L) cm x 1 (D) cm x 1.9 (W) cm in left mid-level 2 that appeared to have an atypical large and star-shaped hilum (Figure 2A) without peripheral vascularity or microcalcification.

Figure 2. Ultrasound of an enlarged node in medial level 2 (submandibular). This node corresponds in location with the FDG-avid nodes on PET scan. The node was 2.8 cm in largest dimension with an oval shape but contained an unusual irregular, large hilum (yellow arrow) seen in the transverse and sagittal sections.

Nearby in the lateral portion of left level 2, a tear-drop shaped hypoechoic mass was seen that measured 1 (L) cm x 0.4 (D) cm x 0.9 (W) cm with hyperechoic linear foci that was avascular. Because of the suspicious nature of both left level 2 nodes, they were biopsied with a 25-g needle. The mid-level 2 node contained benign, mature lymphocytes and a thyroglobulin ,0.2 ng/mL consistent with a benign reactive node. Every time the lateral level 2 node was entered, the patient jumped and cried out in pain. During the second pass, the needle was slowly advanced with direct observation of the tip. The patient immediately complained of pain when the needle tip touched this mass. When the needle was withdrawn 1 mm to 2 mm, the pain stopped and recurred as soon as the needle entered the mass. After two passes in which the needle tip was confirmed within this mass, the biopsy was stopped. The cytology was insufficient because of the lack of cellular material and a thyroglobulin ,0.2 ng/mL.

The painful lateral level 2 mass is traumatic. It has been recently recognized that one or more neuromas occur in our post-thyroidectomy patients after lateral (levels 2, 3, 4 and 5) neck dissection. Interestingly, this patient had evidence of a prior traumatic neuroma in the left level 2 removed at the time of her bilateral level 2 neck dissections performed about 5 years after her initial thyroid surgery.

Figure 3. Ultrasound of a traumatic neuroma in lateral level 2 posterior to the sternocleidomastoid muscle. The mass was teardrop-shaped (yellow arrow) without a hilum, peripheral vascularity or microcalcification. There were subtle short linear hyperechoic foci within the mass (red arrows).

Traumatic neuromas are a non-neoplastic proliferation of nerve tissue that develops at the proximal end of an injured nerve. Most patients have no symptoms. In a recent 2012 review of 202 patients with thyroid cancer after thyroidectomy and lateral neck dissection, 56 traumatic neuromas in 36 patients (17.8%) were found. Fifty-five (98.2%) neuromas showed a direct continuity of a nerve. Traumatic neuromas compared with metastatic nodes were shown to have a smaller short axis (0.36 cm vs. 0.61 cm; P<.001) and a smaller short:long ratio (0.31 vs. 0.61, P<.001). Many of the metastatic nodes, but none of the traumatic neuromas, were located medial to the internal jugular vein. Other important sonographic features of traumatic neuroma include: fusiform shape (P<.001), ill-defined margins (P<.001), mixed echogenicity (P<.001), absence of vascular flow (P<.001) and hyperechoic or hypoechoic lines within the mass. Traumatic neuromas never have a hyperechoic hilar line running parallel with the long length of the node, vascular flow, microcalcification or cystic degeneration.

With the ultrasound probe in the transverse position in the lateral neck, the plexus is located posterior to the sternocleidomastoid muscle in the upper neck (Figure 3) and between the anterior and medial scalene muscle in the lower cervical region. Turning the ultrasound probe in an oblique angle (higher toward the midline), the continuity of the traumatic neuroma with the branches of the cervical plexus can be confirmed by a thin (1 mm to 2 mm AP diameter) hypoechoic linear structure leading into the suspected neuroma. It is important to recognize the sonographic characteristics of traumatic neuromas compared with a metastatic node in the lateral neck to avoid an unnecessary painful biopsy. The pain associated with the biopsy is described as a severe, knife-like or electric pain that occurs as soon as the needle touches or enters the neuroma. A thyroglobulin measured on the needle wash of a traumatic neuroma will be <0.2 ng/mL.

For more information:

Ha EJ. Thyroid. 2011;21:1385-1387.
Ha EJ. Thyroid. 2012;22:820-826.
Kwak JY. J Clin Ultrasound. 2009;37:189-193.

Disclosure:

Lee reports no relevant financial disclosures.