GRANULAR CELL TUMOUR OF THE LARYNX – A CASE REPORT

Granular cell tumours (GCTs) are benign tumours rarely found in the larynx even though they are common in the head and neck region. The laryngeal tumour may be asymptomatic but typically patients present with hoarseness of voice, stridor, haemoptysis and dysphagia. The lesion can mimic squamous cell thus deep biopsy must be taken with adjacent normal tissue to confirm this pathology. Immunohistochemical staining is also used. Complete surgical resection of this tumour is the treatment of choice. We present a 25 year old woman with a laryngeal granular cell tumour involving the right vocal cord diagnosed after direct laryngoscopy and biopsy. She was treated by right cordectomy via a laryngofissure approach. We present the case due to the rarity of the laryngeal granular cell tumour and the need to highlight the importance of taking deep biopsies. If biopsies are superficial, an inexperienced pathologist would mistake it for well differentiated carcinoma.


INTRODUCTION
Granular cell tumor is one whose histology had been a matter of controversy until they were found to be of neuroectodermal origin as demonstrated by immunophenotypic and ultrastructural evidence. 1hese tumours occur commonly in the tongue though they can occur in any part of the body.Granular cell tumours (GCTs) may be benign or malignant though the latter versions are rare (2% of all such tumours).Laryngeal granular cell tumours are rare constituting about 3% to 10% of all cases. 2 We present a case of a granular cell tumor in the larynx and a literature review.

CASE REPORT
This is a 25 year old woman who presented at the Ear, Nose and Throat Clinic of the Cape Coast Teaching Hospital with progressive unremitting hoarseness of voice of a year's duration.The patient had been apparently well until the onset of the hoarseness of voice, which had been, treated on several occasions at various health facilities with no improvement.She thus reported to our clinic.She had been having occasional expectoration of blood-stained sputum and episodes of easy fatigability.She had no associated weight loss, dysphagia, odynophagia or dyspnoea.She occasionally took alcohol and had not been smoking.
On examination, she was a well looking young woman.She was afebrile, anicteric and not pale or dehydrated.Her chest was clinically clear.Her pulse was 90 beats per minute, regular and of good volume.She was conscious and normal.Ears and nose were normal.Oropharyngeal examination was also normal.
Indirect laryngoscopy showed a pale, lobulated mass on the right vocal cord.Both vocal cords moved in abduction and adduction.No neck nodes were palpated.A provisional diagnosis of a right vocal cord tumour was made and patient worked up for direct laryngoscopy.Finding at direct laryngoscopy was an exophytic mass on the posterior half of the right vocal cord as seen in Figure 1.ncision biopsy was taken and sent for histopathology.Histopathology report was as follows: "Sections show a tumour lined in areas by squamous epithelium.The tumour showed plump fibroblast-like cells with granular cytoplasm alternating with areas of homogenous eosinophilic stroma.No evidence of malignancy seen.Diagnosis: Granular Cell Tumour" Patient subsequently had elective tracheostomy followed by laryngofissure and right cordectomy.
Patient had nasogastric tube feeding for 5 days and was decannulated after 7 days.She subsequently recovered well with normal feeding but had an initial weak voice.At six months follow-up, flexible nasolaryngoscopy was done and no evidence of tumour recurrence was found.She has also started speech therapy to improve her voice, which is still hoarse.

DISCUSSION
GCTs were initially thought to be degenerative diseases of mature striated cells thus called myoblastoma by Abrikossoff in 1926. 1 Later S100 immuno-histochemical staining of their cytoplasmic granules showed they were true tumours of neural origin, most likely from Schwann cells.
The origin of these tumours being from schwann cells is also supported by findings on electron microscopy which reveals basement membrane resembling perineurium with surrounding angulated bodies. 3[6] Granular cell tumours histologically are characterized by the following features: single or loose clusters of large rounded, polygonal or elongated cells with dirty, granular cytoplasm as was found in this case.The cells also have indistinct borders with small centrally located nuclei and prominent nucleoli. 7her names given to these tumours are granular cell neuroma or schwannoma or myoblastoma, myoblastic tumour, embryonal rhabdomyoblastoma and congenital epulis. 8e differential diagnoses of these tumours are rhabdomyoma, rhabdomyosarcoma, and alveolar soft part sarcoma.Whilst granular cell tumours are strongly S-100 positive, rhabdomyoma and rhabdomyosarcoma are negative.Also whilst rhabdomyosarcoma and alveolar soft part sarcoma show marked nuclear pleomorphism, granular cell tumours have relatively uniform nuclei with small nucleoli.
The granular cell tumours also have strongly periodic acid-Schiff (PAS) -positive diastase-resistant cytoplasmic granules. 9In children laryngeal papillomatosis is the most common differential diagnosis considered. 10The cause is unknown.These tumours have been reported in all ages though extremely rare in children. 1,4 ur patient was 25 years old.
GCTs present with hoarseness of voice, dysphagia, haemoptysis and otalgia. 11Our case only had hoarseness of voice with occasional expectoration of blood-stained sputum.Since these tumours are slow growing, patients may only notice the change in voice or dysphagia after about 6 months before reporting to a health facility. 8Our patient noticed she had a change in voice but waited a year before reporting to our hospital.This was when the dysphonia was progressively worsening.On examination, laryngeal GCTs appear as rounded firm, submucous tumours covered by normal mucosa.They may be polypoid, cystic or sessile and mostly located on the posterior two-thirds of the vocal cord and arytenoid region.They thus resemble polyps or granulomata.They however can be differentiated from polyps which are soft and glistening compared to GCTs which are fibrotic.Granulomata also mostly result from trauma but macroscopically they are similar to the GCTs in that they are located on the posterior larynx. 3,12 deep biopsies are not taken, because of squamous proliferation on the surface of the lesion and because they show local invasion of adjacent tissue they can easily be mistaken for well-differentiated carcinoma by an inexperienced pathologist. 4,13This may thus be mismanaged by radical surgery such as total laryngectomy.Biopsies must also include normal tissue adjacent to the tumour. 3Our patient's histology was reported to show a tumour lined in areas by squamous epithelium.
Malignant GCT is suspected when the tumour is rapidly growing and ≥4cm in size.Other features of malignancy are nuclear pleomorphism, increased nucleus/cytoplasm ratio, frequent mitosis, cells which are spindle-shaped with necrosis and vacuolated nucleoli. 3he GCT is managed according to the site and extent of the lesion.
Small tumours are managed by endoscopic resection or by thyrotomy with total resection of the tumour.Laryngofissure and partial laryngectomy are used for larger tumours. 1,14Laryngofissure with cordectomy in the presented case was enough for the complete excision of the tumour.Chemotherapy and radiotherapy have not been used to treat these tumours due to fear of inducing malignant transformation. 3currence is uncommon.This has been reported in 2-8% of cases though now it is suggested the cases reported as recurrences might have been new primary tumours as multiple lesions have been reported to occur in various body parts in some patients. 6,15ecurrence may also suggest malignancy.Regular follow-up for at least 3 years with flexible nasolaryngoscopy is key to detecting recurrence early. 3,16

CONCLUSIONS
Laryngeal GCT is rare thus a high index of suspicion is needed to diagnose it.Deep biopsies of the tumour with adjacent normal tissue are necessary for accurate diagnosis.An experienced pathologist must report the histology as these tumours can easily be misdiagnosed as carcinoma.Total resection of the tumour must be done either endoscopically or via laryngofissure or thyrotomy to avoid recurrence.Regular follow-up of these patients is necessary to pick up recurrence early.

CONSENT
Written informed consent was obtained from the patient for publication of this case report and any accompanying images.

Figure 1
Figure 1 Direct Laryngoscopic View of the Right Vocal Cord Tumour (arrowed)