We report herein on a case of spontaneous perforation of the esophagus (Boerhaave’s syndrome) in a 61-year-old man. The pleural effusion specimen was a dirty dark brown liquid and the cytological findings showed scattered orangeophilic superficial or intermediate squamous epithelial cells without atypia as well as bacteria and food in the inflamed pleural effusion. These findings indicated the possibility of an esophageal perforation. Quick diagnosis may improve the survival rate of this disease. Both pathologists and cytologists should pay close attention to dirty black pleural effusion which contains superficial or intermediate squamous cells without atypia.