Understanding primary parotid squamous cell carcinoma e A systematic review O. Edafe a,* , B. Hughes b , P. Tsirevelou c , J. Goswamy d , R. Kumar d a Department of ENT, Sheffield Teaching Hospitals Foundation Trust, UK b Warrington and Halton Hospitals NHS Trust, UK c Department of ENT, Sherwood Forest Hospitals NHS Foundation Trust, UK d Department of ENT, Manchester University NHS Foundation Trust, UK article info Article history: Received 13 January 2019 Accepted 24 March 2019 Available online xxx Keywords: Parotid Parotid malignancy Squamous cell carcinoma abstract Introduction: The true incidence of primary parotid squamous cell carcinoma (SCC) is unknown and likely overestimated in the literature. The aim of this systematic review is to examine the diagnosis, aetiology and incidence of parotid SCC by analysing studies evaluating primary parotid SCC. Methods: A systematic search of Medline, EMBASE and Cochrane library was performed. A narrative synthesis was done. Results: A total of 14 observational retrospective studies on primary parotid SCC were included. There are currently no standard criteria for ascertainment of primary parotid SCC. Primary parotid SCC is thought to be due to squamous metaplasia within the ductal epithelium and subsequent invasive squamous carcinoma. Histological features that favour primary disease includes SCC confined to parotid parenchyma with no direct communication to the skin and the absence of mucin. Incidence of primary parotid SCC varied from 1.54 to 2.8 cases per million person-years. Around 30%e86% of patients recorded to have primary parotid SCC on clinical records, when scrutinised, were in fact secondary to parotid lymph node involvement following regional advancement from skin or upper aerodigestive tract SCC. Conclusion: Primary parotid SCC is rare and it is currently a diagnosis of exclusion. Thor- ough clinical assessment including endoscopy, preoperative imaging and the scrutiny of histopathological findings allow for differentiation between primary and secondary SCC within the parotid. This thus affects both initial treatment and subsequent follow-up. Crown Copyright © 2019 Published by Elsevier Ltd on behalf of Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. All rights reserved. Introduction The parotid gland develops from complex interaction between the oral epithelium and underlying mesenchyme. This epithelial outgrowth is ectodermal in origin. 1 The parotid gland is separated into numerous lobules by connective tissue, each lobule containing secretory units known as acini. Adipocytes tissue aggregates between these lobules. The parotid gland contains serous acini (group of serous epithelial cells interposed by myoepithe- lial cells). The ductal system is lined by columnar and cuboidal epithelial cells partially surrounded by myoepi- thelial cells. 2 Primary parotid squamous cell carcinoma (SCC) is rare. Treatment options include surgery and radiotherapy. In a cohort of 2104 patients, 23% had surgery alone, 49% had adjuvant radiotherapy, 14% had radiotherapy alone, and 14% * Corresponding author. E-mail address: ovieedafe@hotmail.co.uk (O. Edafe). the surgeon xxx (xxxx) xxx Please cite this article as: Edafe O et al., Understanding primary parotid squamous cell carcinoma e A systematic review, The Surgeon, https://doi.org/10.1016/j.surge.2019.03.006 https://doi.org/10.1016/j.surge.2019.03.006 1479-666X/Crown Copyright © 2019 Published by Elsevier Ltd on behalf of Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. All rights reserved.