Anaplastic carcinoma presenting with cervical lymphadenopathy. We describe 50 patients with anaplastic carcinoma presenting with a mass in the neck. The diagnosis of anaplastic carcinoma was confirmed by immunocytochemistry to exclude very poorly differentiated squamous carcinomas, amelanotic melanoma, and non-Hodgkin's lymphoma. The primary site was established immediately in 26 patients (25 in the head and neck; 1 in the lung); a further 4 had radiological evidence of a primary tumour in the lung. The primary site was established later in 1 patient, in the ethmoid sinuses. In 20 patients the primary site was never established. The commonest primary site was the nasopharynx. The basic treatment policy was radiotherapy, although 20% of patients with a known primary tumour, and 50% of those without, were untreated. The 2-year survival was about 30% in both groups, and did not differ significantly. Prognostic factors for survival were age, performance status, and T status of the primary tumour. Sex, node status, node level, and laterality of nodes, were not. 