A 5-year retrospective review of skin adnexal tumours received at a tertiary dermatopathology service: Implications for linked genetic diagnoses.

Background Skin adnexal tumours (SATs) comprise a diverse range of neoplasms, which are difficult to diagnose clinically. They present in paediatric and adult populations, and may be indicative of an underlying genetic syndrome. There is a lack of recent data on the presentation of these tumours in clinical practice in European populations. Objective To characterise the clinical and pathological features of SATs received at a single tertiary centre over a 5-year period. Methods A retrospective health record audit of SATs received at the Department of Cellular Pathology, Royal Victoria Infirmary, Newcastle upon Tyne Hospitals NHS Foundation Trust, during the period November 2012 to October 2017. Results 107144 skin cases were received during the audit period. 1615 cases of SATs from 1359 patients were included; 1570 (97.2%) were benign and 45 (2.8%) were malignant. Overall, the average age at presentation was 55 years (range 11 months - 97 years) and the male to female ratio was 0.77:1. Sweat gland and hair follicle SATs were most frequently excised; in adults the most frequent tumour was hidrocystoma, and in children, pilomatrixoma. Pre-biopsy diagnosis was correct 28% of the time. Benign SATs are often markers of an associated genetic condition, warranting improved discrimination of sporadic from genetically related SATs. Conclusions SATs are difficult to diagnose clinically, and clinicopathological correlation may help enhance selection of genetically related SATs from sporadic cases. These data have implications for clinical and dermatopathological training provision, the development of reporting standards, and genetic assessment of selected patients.