A rare benign tumour—granular cell tumour of the larynx

Granular cell tumours (GCTs) are usually benign neoplasms, believed to originate from Schwann cells. They can occur in any part of the body, with approximately 50% arising in the head and neck region, and 3–10% of cases involving the larynx.^1,2 Adults have a 5–16% risk of multifocal disease, with higher rates reported in patients with respiratory tract involvement.^2,3 The mean age at diagnosis is 45 years, with a slight female predominance (female-to-male ratio of 3:2).¹ Malignant GCTs are very rare, but when present they tend to metastasise and carry a poor prognosis.² We present a case of this rare tumour and discuss its management in the New Zealand context.

Case

A 42-year-old woman was referred to the ear, nose and throat outpatient clinic with a 1-year history of dysphagia and dysphonia, with no weight loss. Head and neck examination was unremarkable. Endoscopic evaluation revealed a smooth, white mass over the right arytenoid. Contrast-enhanced computed tomography (CT) of the neck demonstrated a solid, well-defined 1cm lesion just superior to the arytenoid cartilage, with no abnormal cervical lymphadenopathy.

The patient underwent laryngoscopy and biopsy. Histology confirmed a GCT without malignant features. Pseudoepitheliomatous hyperplasia of the squamous epithelium was noted, and S100 immunostaining was strongly positive in the granular cells. Given the small biopsy sample, a sinister lesion could not be absolutely excluded.

View Figure 1–3.

The patient proceeded to definitive excision with CO₂ laser. The lesion was excised from the arytenoid cartilage, and Kenacort A40 was injected locally at the surgical site. Histology revealed the tumour extended to a cauterised deep and peripheral margin that was located at the posterior glottic commissure. The risks of posterior glottic stenosis were discussed, and the patient preferred initial monitoring. This approach was also supported by the very low risk of laryngeal recurrence reported in the literature, with recurrence rates reported to be less than 2% in all cases, including in cases with positive margins.² The patient was followed up in similar manner to an early treated glottic malignancy, 2-monthly for 4 months, then 4-monthly. Recurrence was identified with clinical follow-up and CT at 18 months post-operatively. The case was reviewed at a head and neck multidisciplinary meeting, with advice sought from a subspecialist laryngologist out of the region. After discussion with the patient, the decision was made to proceed with re-excision. The patient underwent CO₂ laser excision with intraoperative frozen section and post-cricoid advancement flap (Figure 2). Frozen sections were negative for residual tumour. Two weeks later, she returned to theatre for injection of Kenacort A40 and topical mitomycin to reduce fibrosis. At 4 months post-operatively, the operative site had healed well and there was no evidence of recurrence (Figure 3). The patient’s voice improved after the initial excisional biopsy and remained stable after thereafter. The patient is under ongoing clinical surveillance.

Discussion

Eighty-five percent of GCTs present with dysphonia.² Other symptoms include dysphagia, cough, haemoptysis, dyspnoea and stridor.^1,2 Endoscopically, lesions are typically firm, polypoid or nodular, and range in colour from yellow to grey or white. In adults, about 50% of GCTs arise from the true vocal fold, 11% at the arytenoid region and 5% at the posterior commissure.² Children are more likely to get subglottic involvement.¹ Mur et al. reported that 49% of paediatric GCTs were subglottic.⁴ These findings suggest that a cautious approach may be warranted for GCTs in children, as subglottic involvement may increase the risk of airway obstruction.

Diagnosis of a GCT requires a biopsy. Characteristic histological findings include large polygonal cells with eosinophilic granular cytoplasm. Pustulo-ovoid bodies of Milian present in 66–76% of cases, and pseudoepitheliomatous hyperplasia are present in 33–65% of cases. Immunohistochemistry is strongly positive for S100 and CD68. Eleven percent of cases are initially misdiagnosed as squamous cell carcinoma.² Although generally benign, GCTs may show features such as infiltrative growth, perineural invasion and vascular invasion.³ Mobarki et al. reported that 2–11% of GCTs of different anatomical sites (including larynx) could be classified as malignant, with distant metastasis occurring in approximately 2% of cases.^3,5,6

There is no established treatment guideline for GCTs. Surgical excision is the primary treatment option, as GCTs are generally resistant to radiotherapy and chemotherapy. A systematic review of 200 patients found 70% of patients received simple surgical excision. Additional surgical treatment included laryngectomy, tracheostomy, neck dissection, tracheal resection, pharyngectomy and cricothyrotomy. Four patients received radiation and three received chemotherapy; half had malignant disease.²

Reported recurrence rates range from 2% overall, with average follow-up time of 36 months, to as high as 20% in GCTs excised with positive margins at other anatomical sites.^2,3 In paediatric patients, recurrence has been reported in 15% of cases with a median follow-up time of 12 months.⁴ Long-term follow-up is therefore essential to detect recurrence early, as it will reduce functional compromise from bulky lesions requiring more aggressive surgery.^4,7–13 In summary, GCTs in the larynx are rare and there are no current treatment guidelines. Although typically benign, they can affect laryngeal function and carry a risk of recurrence if not completely excised. Careful surveillance is therefore essential for early detection and to facilitate timely surgical intervention and minimise long-term functional morbidity.