Benign anlage tumour: a very unusual neck mass.

A 44-year-old woman presented with a slow-growing asymptomatic neck swelling at the left medial clavicle. Haematological and biochemical work up was normal and an ultrasound confirmed the swelling, but needle aspiration was non-diagnostic. As lymphoma was the main differential diagnosis, the swelling was completely excised. Immunohistochemistry yielded a rare lesion, suspected to represent a myoepithelial/mixed cellularity tumour of soft tissue. The extreme rarity of these tumours required a confirmatory secondary opinion, which ultimately led to it being identified as a benign anlage tumour (previously known as an ectopic hamartomatous thymoma) This case highlights the fact that thorough assessment of patients with neck swellings should be undertaken to rule out sinister causes-keeping in mind more rare differentials-helping to guide final management.