Tuberculous Parotitis a Case Report

Tuberculosis(TB) of the parotid gland is a rare clinical condition which can mimic a neoplasm. We report a 39 year old lady from high social class with right sided parotid gland tuberculosis who underwent subtotal parotidectomy. She presented with right sided painful and progressive preauricular swelling of 6 month duration, associated with ipsilateral painless level V lymph node enlargement. Examination revealed firm right parotid mass measuring 8x4cm, tender and fixed, with tethering of the overlying skin. She was otherwise healthy looking. Fine needle aspiration cytology showed pleomorphic adenoma. The diagnosis of parotid tuberculosis should be made with high index of suspicion. In case of missed pre-operative diagnosis, intra-operative frozen section will obviate the need for extensive surgery.

Case report
A 39 year old lady from high social class presented to our otorhinolaryngology clinic with a history of painful right preauricular swelling of 6 month duration. There was no history of fever, night sweat or weight loss. There was no associated cough or chest pain, and she denied any history of close contact with person suffering from tuberculosis.
On examination, the right parotid swelling was about 4x8 cm in size and fixed to underlying structures. The skin over the swelling was hyperemic and tethered. The ears appeared normal. No abnormalities were noted on intra oral examination. There was a tender ipsilateral level V lymph node measuring 2cm in greatest dimension. She was otherwise healthy looking.
Ultrasonography (USS) showed both the parotid swelling and level V node to be cystic. However, the USS guided fine needle aspiration cytology (FNAC) was suggestive of pleomorphic adenoma. Computerised tomography of the parotid region revealed an isodense, lobulated, non-enhancing mass abutting on the anterior wall of the external auditory canal with no evidence of bony erosion. HIV test was non-reactive and the full blood count was within normal limits.
A diagnosis of right parotid gland tumour was made and the patient booked for parotidectomy. The findings at surgery were extracapsular infilterative parotid mass involving the skin, facial nerve and temporal bone. Therefore, a sub-total parotidectomy was done. The histology revealed features of tuberculosis.
Post-operatively, she developed facial nerve paralysis which improved remarkably with aggressive physiotherapy.
She was subsequently placed on anti-tuberculosis regimen consisting of isoniazid, rifampicin and ethambutol, with remarkable clinical improvement.
Discussion
Tuberculosis of the parotid gland is rare, even in Asia or Sub-Saharan Africa where pulmonary tuberculosis is endemic. In Nigeria, the estimated incidence of TB is 311 (all new cases per 100,000 population).1 However, that of TB parotitis is not known. Tuberculous adenitis or parotitis could present as a lump thereby mimicking a neoplastic lesion. Most of the tumours of salivary gland origin arise from the parotid gland, of these, 80% are benign. Eighty percent of the benign tumours are pleomorphic adenoma.2
Clinically, it is difficult to distinguish between tuberculous salivary gland disease and a neoplasm. It is therefore important to differentiate the two forms, as tuberculosis of the salivary gland can be treated medically, thus avoiding any potential surgical complications.
A normal chest radiograph and negative Mantoux test do not exclude TB, particularly extrapulmonary cases. The appearances on computerised tomography (CT) scanning may mimic both inflammatory and neoplastic lesions. In a study by Riley et al, FNAC was found to have an overall accuracy rate of 86% in diagnosing parotid lesions.3 FNAC has been advocated as a simple and easy method of diagnosing parotid gland tuberculosis.4 However, the histopathological examination of the specimen remains the definitive diagnostic test. The use of interferon-? T-cell assays, especially in low-incidence settings looks promising. This test uses an enzyme-linked assay to detect T-cells specific for the M. tuberculosis proteins ESAT-6 and CFP-10, which are absent in the Bacillus Calmette-Guerin (BCG) vaccine and in most environmental mycobacteria. The test is not confounded by BCG immunization and has better correlation with TB exposure than Mantoux testing, suggesting a role in settings where the bacterial burden is low.5
Even though TB of parotid is rare, the diagnosis should be considered with high index of suspicion in patients with parotomegaly. In case of missed diagnosis prior to surgical excision, intra-operative frozen section will obviate the need for extensive surgery, which is fraught with complications.

References

1. Global Tuberculosis Control. WHO REPORT: 2008; 129
2. Roland NJ, McRae RDR, McCombe AW. Key Topics in Otolaryngology and Head and Neck Surgery. 2nd ed. Oxford: BIOS; 2001. p 275
3. Neil R, Robert A, Scott S. fine-needle aspiration cytology in parotid masses: our experience in canterbury, new Zealand. ANZ J. Surg. 2005; 75: 144?146
4. Subramanian S, Abdul R, Faizah A. Tuberculosis of Parotid Gland: A Rare Differential Diagnosis of Parotid Tumor. The Internet Journal of Head and Neck Surgery. 2007. Volume 1 Number 2.
5. Lalvani A. Diagnosing Tuberculosis Infection in the 21st Century: new tools to tackle an old enemy. Chest. 2007; 131:1898?906.

by
Salisu Aa, Lasisi O A b, Aremu S Kc
a, c Senior Registrars ORL Department, University College Hospital, Ibadan
b Senior Lecturer ORL Department, College of Medicine, University of Ibadan/Consultant ENT Surgeon University College Hospital, Ibadan
Correspondence to: Salisu A
Email: [e-mail]