LAUSR

Argyris and Koutlas [1] have described a single cystic lesion of orthokeratinized odontogenic cyst (OOC) and odontogenic keratocyst (OKC) with focal ghost cell keratinization/ calcification in a patient with Gardner syndrome. They speculated that two distinct types of keratinizing OCs occurred simultaneously as separate foci within the same lesion under the common molecular (Wnt/β-catenin) pathway, since examination of multiple sections revealed that at no point were the two cysts in continuity. This is an interesting contribution demonstrating the morphological diversity that OCs may show [2–4]. Here we add an unusual case of calcifying odontogenic cyst (COC) in which the unicystic epithelium combined areas resembling dentigerous cyst (DC), OOC and OKC, with a minor component of mucous cells and duct-like structures. The COC lining also showed occasional granular parakeratosis (GP). The patient, a 33-year-old man, presented with a painless facial swelling. The left maxilla was occupied by a well demarcated, unilocular cystic lesion measuring 4 cm in largest dimension. It contained the crown of an impacted canine and showed a 1-cm radiopaque mass within the basal portion of the lesion. Radiographic follow-up at 5 years showed no recurrence. Histologically, the enucleated cyst had a single cavity with a small luminal nodule (Fig. 1). This polypoid proliferation resembled plexiform ameloblastoma, but contained ghost cells, calcification or dentinoid (COC). Considerable variation in the morphology of the epithelial lining was found; it was mostly simple, non-keratinized thin or hyperplastic squamous (DC-type) epithelium, but parakeratinized (OKC-type) and orthokeratinized (OOC-type) areas were also seen (Fig. 2). Another part of the cyst epithelium had mucous cells and duct-like structures (microcysts), and such foci were in part indistinguishable from glandular odontogenic cyst (GOC) (Fig. 2). In addition to ghost cells, the COC-type epithelium contained a few ameloblastlike cells housing small fine to large coarse keratohyaline granules (GP) (Fig. 3). The diagnosis of COC with focal para/orthokeratinization and mucous cell differentiation was made. In most cases, it is possible to classify OCs readily into one of the existing entities. There remains a small group of complex lesions in which different types of OC are combined. Various combinations and proportions of histological components have been reported in these polymorphous OCs, and no two cysts have looked precisely the same: COC with OOC [5], COC with OKC [6], OOC with OKC and ghost cell keratinization/calcification [1], GOC with DC [7], GOC with OKC and OOC [8], GOC with squamous differentiation [9–11], GOC with paraor orthokeratinization [12, 13] and GOC with ghost cell keratinization [14]. Although the literature is replete with observations of the respiratory epithelium in OCs including OKC [2–4, 15, 16], neither intraepithelial mucous cell nor duct-like structure has been recognized as part of the morphological spectrum of COC and OOC. The occurrence of mucous secreting cells in the present maxillary OC may be the result of metaplasia or prosoplasia because of no sinonasal involvement [4]. In view of the fact that mucin-laden goblet cell is known as an example of single-cell gland, it is possible that additional * Fumio Ide [email protected]