Re: Salivary gland swellings
We read with interest the article by Mehanna et al1 about salivary gland swellings and felt that the section on obtaining a tissue diagnosis merited further comment.
Obtaining an accurate and timely pre-operative tissue diagnosis is essential in the parotid glands in particular, as this allows informed patient consent, discussion about potential facial nerve injury and pre-operative planning. Surgery can also be avoided in some pathologies, such as Warthin’s tumour, particularly in those patients who are elderly or unfit. Parotid neoplastic diagnosis revolves around triple assessment, comprising clinical examination, imaging (usually ultrasound in the first instance) and needle biopsy, as per the breast model.
Fine needle aspiration cytology (FNAC) has traditionally been the biopsy technique of choice in the parotid glands. FNAC is quick and safe and is capable of a high degree of accuracy but requires optimised circumstances to perform effectively (ultrasound guidance, available onsite cytologist/technician , ancillary cytological techniques). In everyday clinical practice however, these optimised conditions are rarely, if ever, available and most FNAC is done free-hand, without image guidance in the clinic setting. This is reflected in the significant heterogeneity in FNAC performance demonstrated in the meta-analysis by Schmidt et al.(2) Additionally, FNAC can only provide a cellular aspirate and it is inherently limited in the diagnosis of a parotid malignancy, with a relatively poor sensitivity (2) and high false negative rate (3). It is also limited in the diagnosis of lymphoid proliferation (namely differentiation of reactive node versus low grade lymphoma) and in these cases will usually act only as an indicator of the need for excision. As a consequence of the perceived high non-diagnostic rate and poor sensitivity for malignancy of FNAC, the technique of ultrasound-guided core biopsy (USCB) has undergone evaluation in the parotid glands(4).
USCB involves the use of a small bore needle (usually 18G, 1.2mm size) to obtain a core of tissue from solid areas of the lesion under ultrasound guidance. Local anaesthetic is required but the procedure is quick and generally well tolerated in the outpatient setting--it is not generally painful as suggested by the authors. Crucially, the core of tissue allows formal immunohistochemical analysis with improved typing and grading of tumours and differentiation of lymphoid hyperplasia. Ultrasound guidance allows avoidance of the intra-parotid vessels and facial nerve and tumour seeding is not reported with small bore needles. USCB is a safe procedure with no significant complications reported and has also demonstrated high diagnostic accuracy in several series. The meta-analysis by Schmidt et al.(5) confirmed not only improved accuracy of USCB over FNAC but also a lack of significant heterogeneity of results in the USCB studies and reduced non-diagnostic rates (accepting a relatively small number of studies in the USCB meta-analysis). With increasing acceptance and availability of USCB it is likely that in many units there will be a replication of what has already occurred in breast biopsy practice, where USCB has largely replaced FNAC as the biopsy diagnostic tool of choice.
Edward Sellon, radiology SpR, Eastbourne District General Hospital, Eastbourne, UK
Andrew Moody, Consultant Maxillofacial surgeon, Eastbourne District General Hospital, Eastbourne, UK
David Howlett, Consultant head and neck radiologist, Eastbourne District General Hospital, Eastbourne, UK
Competing interests: None declared.
1 Mehanna H, McQueen A, Robinson M, Paleri V. Salivary Gland Swellings. BMJ 2012; 345: 36-41
2 Schmidt RL, Hall BJ, Wilson AR, Layfield LJ. A systematic review and meta-analysis of the diagnostic accuracy of fine-needle aspiration cytology for parotid gland lesions. Am J Clin Pathol 2011; 136(1): 45-59
3 Balakrishnan K, Castling B, McMahan J, Inrie J, Feeley KM, Parker AJ. Fine needle aspiration cytology in the management of a parotid mass: a two centre retrospective study. Surgeon 2005; 2: 67-72
4 Breeze J, Andi A, Williams MD, Howlett DC. The use of fine needle core biopsy under ultrasound guidance in the diagnosis of a parotid mass. Br J Oral Maxillo fac Surg 2009; 47(1): 78-79
5 Schmidt RL, Hall BJ, Layfield LJ. A systematic review and meta-analysis of the diagnostic accuracy of ultrasound guided core needle biopsy for salivary gland lesions. Am J Clin Pathol 2011; 136(4): 516-526
Competing interests: No competing interests