Actinomycosis in fine needle aspiration cytology.

Four cases of actinomycosis were diagnosed by fine needle aspiration (FNA) cytology and eight more cases were detected during a review of FNA smears reported as inflammatory. The age of these 12 cases ranged from 20 to 61 years with a median of 35 years. The male to female ratio was 3:1. The common regions of involvement were cervicofacial in seven cases (58.3%), thoracic in three (25.0%) and abdominal in two (16.7%). Four of the seven cervicofacial cases presented with intra-oral masses; the thoracic lesions were pulmonary in location, and the abdominal lesions presented as bowel masses. The possibility of actinomycosis was not considered clinically in any case. The main reason for missed cytodiagnosis in two thirds of the cases appeared to be observer error. It is suggested that when the aspiration smear from a mass is found to be an inflammatory exudate rich in neutrophils, special efforts must be made to look for this microorganism.