title: High-grade transformation of adenoid cystic carcinoma delineated with a fibrous rim: a case report.
abstract: BACKGROUND
  High-grade transformation or dedifferentiation in carcinoma is progression of a low-grade malignant neoplasm to a high-grade carcinoma or poorly differentiated adenocarcinoma. This is rarely observed in adenoid cystic carcinoma of the salivary glands.
  
  
  METHODS
  A 39 year-old woman presented with a painless mass at the left submandibulary region that had been growing slowly for 5 years. Submandibulary mass resection revealed a mass with peripheral adenoid cystic carcinoma and a central high-grade tumor delineated with a fibrous rim, raising the possibility of a hybrid or composite carcinoma, requiring differential diagnosis depending upon morphology and immunohistochemistry findings. The final histopathological diagnosis was high-grade transformation of adenoid cystic carcinoma. After surgical therapy, the patient was irradiated to the neck and submandibulary region. No sign of tumor recurrence has been evident for 36 months.
  
  
  CONCLUSIONS
  This present case seems to be another rare case with high-grade transformation of adenoid cystic carcinoma and the fibrous rim may be a histopathological feature of such cases, which should be kept in mind.
authors.affiliation: Department of Pathology, Kahramanmaraş Sütçü İmam University Faculty of Medicine, Kahramanmaraş, Turkey.
authors.forename: Hamide
authors.initials: H
authors.lastname: Sayar
authors.affiliation: Department of Pathology, Dokuz Eylül University Faculty of Medicine, İzmir, Turkey.
authors.forename: Sülen
authors.initials: S
authors.lastname: Sarıoğlu
authors.affiliation: Department of Pathology, Kahramanmaraş Sütçü İmam University Faculty of Medicine, Kahramanmaraş, Turkey.
authors.forename: Sevgi
authors.initials: S
authors.lastname: Bakariş
authors.affiliation: Department of Otolaryngology, Kahramanmaraş Sütçü İmam University Faculty of Medicine, Kahramanmaraş, Turkey.
authors.forename: Ilhami
authors.initials: I
authors.lastname: Yıldırım
authors.affiliation: Department of Otolaryngology, Necip Fazıl Şehir State Hospital, Kahramanmaraş, Turkey.
authors.forename: Hüseyin
authors.initials: H
authors.lastname: Oztarakçı
keywords: Adenoid cystic carcinoma; dedifferentiation; high-grade transformation; submandibulary gland