Synchronous Melanoma: A Single‐Centre 5‐Year Retrospective Study

ABSTRACT Background Synchronous melanoma (SM) is defined as ≥ 2 melanomas diagnosed at the same time, or within 3 months of diagnosing the first melanoma, and occurs rarely. Objectives The objective of this study was to review all the cases of SM discussed at the melanoma MDT meeting in our cancer centre over the last 5 years. Methods Melanoma MDT lists, histopathology and clinical records were reviewed from July 2018 to July 2023 inclusive, for new SMs. This study includes invasive malignant melanoma (MM), lentigo maligna (LM) and melanoma in situ (MIS). Results 1082 patients were diagnosed with cutaneous melanomas over the 5‐year period. Of these patients, 33 patients (3.05%) with SMs were identified in 21 males and 12 females. Ages ranged from 44 to 93 years. Twenty‐four patients (72.7%) had SMs diagnosed at the same time and nine (27.3%) had subsequent melanoma diagnosed within a 3‐month period. Risk factors noted included family history of melanoma (6.06%, n = 2), history of immunosuppression (12.1%, n = 4), and history of previous non‐melanoma skin cancer (6.06%, n = 2). Of the total number of SMs ( n = 68), 26.5% ( n = 18) were invasive, 20.6% ( n = 14) were LMs and 52.9% ( n = 36) were MIS. Most lesions (33.9%, n = 21) were located on the trunk, with 13 (62%) on the back. Sixteen (48.5%) patients had both synchronous in situ lesions, 16 patients had LM/MIS with an invasive melanoma (pathological stage 1a to 4b) and 1 (2.4%) patient had stage 1a with stage 1b melanoma. Conclusions To the best of our knowledge, this is the largest retrospective study to date of SM. It highlights the importance of a full skin check especially once a melanoma has been identified, to ensure further melanomas are not missed.