A 37-year-old man presented with a painless circumscribed nodule that had been gradually enlarging in the left parotid gland area for six years. No cervical lymphadenopathy was detected. A subtotal parotidectomy was performed and a tumour was excised. No tumour recurrence was observed 18 months after the surgery.
Grossly, the tumour was completely circumscribed within the parotid gland, measuring 20×18×15 mm in size. The cut surface revealed multilocular cystic spaces. No bleeding or necrosis was detected in the tumour.
Histologically, the tumour consisted mainly of multiple cystic formations lined with stratified squamous epithelium lacking a granular layer, but containing keratin material and calcification (). There was no evidence of cytological atypia or abnormal mitotic activity in the epithelium. No tubules, duct-like glandular structures, or sebaceous differentiation were observed. No evidence of skin appendages was found beneath the epithelium. The stroma of the tumour was predominantly a dense lymphoid element. The tumour cells stained negatively with periodic acid-Schiff (PAS) and Alcian blue.
Figure 1 H&E stained sections showing the keratocystoma morphology. (A) Characteristic tumour view consisting of variably sized and shaped cystic lesions filled with lamellar keratin material and calcification (×20). (B) The stroma of the tumour (more ...)
By immunohistochemistry, the tumour cells were diffusely positive for cytokeratins AE1/AE3 and 5/6, focally positive for cytokeratin 7, and stained strongly for p63, but weakly for p53 (). The basal cells of the stratified epithelium were partially positive for cytokeratin 19. The tumour cells were completely negative for cytokeratins 8/18 and 20. Less than 1% of all tumour cells were Ki-67 positive.
Figure 2 Immunohistochemical findings in the keratocystoma specimen. The tumour cells strongly stained for AE1/AE3 (A), CK5/6 (B), and p63 (C), or weakly stained for p53 (D) in the keratocystoma case. Inset images show positive cells in the region. All sections (more ...)