Soft-tissue keratocyst: report of 3 new cases from Brazil.

Objective: To describe the clinicopathological features of 3 new cases of soft-tissue keratocyst (STK) of the buccal mucosa from Brazil.

Materials and methods: Clinical data from 3 patients diagnosed with STK were obtained from the archives of the Laboratory of Oral Pathology at the Federal University of Rio de Janeiro- Brazil from 2020 to 2023. Two oral pathologists reviewed conventional hematoxylin and eosin-stained slides of each case. Immunohistochemical stainings for CK19, Bcl-2, CD138, D2-40, EMA, and Ki-67 were performed in all cases.

Results: Case 1 was a 58-year-old man with a 2-year history of painless swelling of the right buccal mucosa, measuring approximately 5 cm. Case 2 was of a 44-year-old man with a painful swelling in the left buccal mucosa lasting 3 years with drainage to the oral cavity. Case 3 was of a 74-year-old woman with a painful swelling in the left buccal mucosa of unknown duration. Microscopic evaluation of all 3 cases revealed a cyst lined with a few cell layers composed of columnar palisading basal cells and a corrugated parakeratin surface. The capsule comprised fibrous connective tissue with variable amounts of blood vessels with hemorrhage, nerve bundles, fat tissue, striated muscle fibers, and the absence of pilosebaceous units. No recurrence was observed after complete surgical removal. All epithelial layers of the 3 cases expressed positivity for CK19 and CD138, the basal cells were positive for Bcl-2 and D2-40, and the superficial epithelial layer was positive for EMA. All cases demonstrated a low proliferation index by Ki-67.

Conclusion: This study represents a series of 3 cases of STK that affected the posterior buccal mucosa of middle-aged patients from Brazil, sharing histopathological and immunohistochemical features with odontogenic keratocyst.