We report the case of a 66-year-old Iranian woman with a phaeohyphomycotic cyst (approximately 3x2.5cm in size) on the right lateral side of the neck. She had dysphagia and hoarseness, without any pain. She complained about discharge of black liquid on the skin and irritation. Histological examination of biopsy fragments from the lesions showed septate, branched brown hyphae. The fungus was cultured, but sporulation remained absent from 4- week-old cultures on Sabouraud dextrose agar (SDA), malt extract agar (MEA), potato dextrose agar (PDA), and water agar with sterile filter paper. Identification with the genus Chaetomium was achieved by sequencing the internal transcribed spacer (ITS) and the small subunit (SSU) domains of the rDNA gene and comparison with sequences held at GenBank and at the Centraalbureau voor Schimmelcultures (CBS). Sequencing of the SSU rRNA gene reveals this strain as belonging to the genus Chaetomium. The sequence of ITS did not fully match with any sequence of available ex-type strains of Chaetomium, Thielavia, Madurella and Papulaspora and hence might belong to an undescribed species. However, without diagnostic morphological features the taxon cannot be introduced as a novel member of the genus Chaetomium. After local excision of the cyst and antifungal therapy with ketoconazole (200mg twice a day), the lesion regressed and healed completely. ; We report the case of a 66-year-old Iranian woman with a phaeohyphomycotic cyst (approximately 3x2.5cm in size) on the right lateral side of the neck. She had dysphagia and hoarseness, without any pain. She complained about discharge of black liquid on the skin and irritation. Histological examination of biopsy fragments from the lesions showed septate, branched brown hyphae. The fungus was cultured, but sporulation remained absent from 4- week-old cultures on Sabouraud dextrose agar (SDA), malt extract agar (MEA), potato dextrose agar (PDA), and water agar with sterile filter paper. Identification with the genus Chaetomium was achieved by sequencing the internal transcribed spacer (ITS) and the small subunit (SSU) domains of the rDNA gene and comparison with sequences held at GenBank and at the Centraalbureau voor Schimmelcultures (CBS). Sequencing of the SSU rRNA gene reveals this strain as belonging to the genus Chaetomium. The sequence of ITS did not fully match with any sequence of available ex-type strains of Chaetomium, Thielavia, Madurella and Papulaspora and hence might belong to an undescribed species. However, without diagnostic morphological features the taxon cannot be introduced as a novel member of the genus Chaetomium. After local excision of the cyst and antifungal therapy with ketoconazole (200mg twice a day), the lesion regressed and healed completely.