Identification of carcinoma origin by thyroid transcription factor‐1 immunostaining of fine needle aspirates of metastases

Abstract

Identification of carcinoma origin by thyroid transcription factor-1 immunostaining of fine needle aspirates of metastases To assess the diagnostic potential of thyroid transcription factor-1 (TTF-1) immunocytochemical staining for identifying the origin of unknown primary cancers from fine needle aspiration cytology (FNAC) of metastases. Immunostaining with TTF-1 was conducted on FNACs suggesting metastatic carcinoma in 128 patients with unknown primary tumours as part of the initial diagnostic procedure. The majority of patients (78) presented with neck masses, four had lung lesions and 46 had masses at other locations. The patients' files were reviewed to obtain data on tumour origin. Thirty-seven of 128 (28.9%) cases stained positive with TTF-1. Pulmonary origin of metastases was confirmed in 27 cases, and four lung lesions were primary lung adenocarcinoma. Two patients had primary and one had mestastatic thyroid carcinomas. In two patients, no follow-up data was available. In one patient, the origin of the primary could not be determined at autopsy. TTF-1 was negative in 18 patients with subsequent diagnosis of metastatic pulmonary cancer and in seven patients diagnosed clinically and radiologically as most probably having a lung carcinoma. In 60 TTF-1 negative patients, the primary tumour originated in other organs (34) or remained unknown (26). TTF-1 immunostaining of FNAC in patients with metastatic carcinoma of unknown origin identified primary pulmonary or thyroid carcinomas in nearly a third of cases. Patients with TTF-1 positive metastases could avoid further extensive diagnostic investigations for the origin of the primary site.