Evaluation of stromal myofibroblasts expression in keratocystic odontogenic tumor and orthokeratinized odontogenic cysts: A comparative study

Abstract

Objective: Keratocystic odontogenic tumor (KCOT) has an aggressive clinical course and a high tendency of recurrence, while orthokeratinized odontogenic cyst (OOC) has different characteristics and does not show aggressive behaviour. Even the treatment of these two lesions varies considerably. A large number of epithelial molecules have been studied in order to differentiate odontogenic keratocyst (OKC) from OOC, but stromal factors have not been adequately studied. Recently, tumor stroma has evolved as a particular field of interest. In the present study, we aim to evaluate and compare the expression of stromal myofibroblasts (MFs) in these entities and correlate it to its aggressive behavior. The term 'keratocystic odontogenic tumor' has been introduced by WHO in 2005 for odontogenic keratocyst keeping in mind its aggressive behavior, however still many pathologists and clinicians use the term OKC synonymously.

Materials and methods: A total of 10 cases of KCOT and 10 cases of OOC were stained for alpha-smooth muscle actin (αSMA) for demonstration of stromal MFs. MF frequency was assessed as the number of αSMA-positive stromal cells in 10 high power fields, presented as the mean number of positive cells per field.

Results: Counts showed that the mean number of positive cells in KCOT (20.6 ± 2.05) was significantly higher than that seen in OOC (10.4 ± 1.06) (P < 0.05).

Conclusion: The different behaviors of these lesions are compatible with the finding of the present study. The increased number of stromal MFs in KCOT in comparison to OOC correlates with its aggressive behavior and increased tendency towards recurrence.

Keywords: Keratocystic odontogenic tumor; orthokeratinized odontogenic cyst; stromal myofibroblasts; αSMA.

Figure 1

Lining of KCOT showing palisaded basal layer of tall columnar cells with reversal of nuclear polarity. The surface exhibits parakeratinization. Subepithelial connective tissue shows radially arranged collagen fibers (H&E stain, ×200)

Figure 2

Orthokeratinized odontogenic cyst: Stratified squamous epithelial lining with surface thick layer of orthokeratin (H&E stain, ×100)

Figure 3

KCOT: Subepithelial connective tissue shows alpha-smooth muscle positive cells radially arranged parallel to each other (IHC stain, ×200)

Figure 4

αSMA positive cells present only in the wall of blood vessels, while subepithelial connective tissue shows very few scattered cells. (IHC stain ×200)