Malignant melanoma of the sympathetic chain: with a consideration of pigmented nerve sheath tumours.

A case of malignant melanoma of the posterior mediastinum, arising from the sympathetic chain is reported. The structural features and the presence of long-spaced collagen on electron microscopic examination suggest schwannian derivation of the tumour. Similar tumours are reviewed and the histogenesis of pigmented nerve sheath tumours in general is discussed. The term 'malignant melanotic schwannoma' is probably the most appropriate for the tumour entity described here.