Acute suppurative appendicitis with Blastocystis hominis

Blastocystis hominis (B. hominis) is an anaerobic protozoan parasite, which lives in human and animal's intestines. It is commonly found in the tropical area. The parasite is low pathogen and its infection causes gastrointestinal disease with diarrhea symptom as reported from many studies. B. hominis is rarely seen in tissue section. The clinical diagnoses are usually confirmed with the microscopic examination of the stool, which can directly detect the parasite through trichrom stain and Kinyoun acid fast technique. We reported a case of 52 years old man with abdominal pain and suspected as perforated appendicitis and tumor of appendix as the differential diagnosis. The macroscopic features of the appendix mass were 7 cm in length and 1.5-2.5 cm in diameter. The cut section showed a widening of the appendix lumen, and the distal part filled with a gelatinous mass. The microscopic examination with HE stain showed the infiltration of PMN inflammatory cells in the muscle layer of the appendix and foci of a number of round structures in the sub mucosal layer known as B. hominis. Some authors reported results from the endoscopy and biopsy examinations that B. hominis does not infiltrate in the intestinal mucosa; nevertheless, in this case we found the infiltration of the parasite towards the mucosal and sub mucosal layers of the appendix.