A 23-year-old man was referred to our department to take radiographs for orthodontic treatment. Accidentally, multiple radiolucent lesions were found on panoramic radiograph (Fig. 1) and there was an evidence of bone defect in the premaxilla. Postero-anterior skull radiograph showed falx cerebri calcification (Fig. 2).

Clinical examination revealed a frontal bossing and hypertelorism as well as an evidence of previous lip closure. No skin lesion was detected. Two major criteria (multiple jaw cysts and falx cerebri calcification) and some congenital anomalies (cleft lip and palate, frontal bossing, and moderate hypertelorism) strengthened the possibility of Gorlin-Goltz syndrome. Patient referred for advanced imaging evaluation.

CT scan showed an expansile lytic lesion in the right antrum pericoronal to the impacted tooth (3×3 cm) and a small lytic lesion between maxillary lateral incisor and canine (Figs. 3A and B). There was a mucous retention pseudocyst in the left antrum with iso-attenuation (Fig. 3C). Three isolated expansile lytic lesions were found in the mandible (Fig. 3D). Expansion and thinning of the cortex was found on the medial wall of the left ramus (Fig. 3E).

Four out of five lesions were detected using ultrasonography (US) (Fig. 4). All lesions were well defined hypoechoic in B mode except the right maxillary cyst with a mixed echogenicity. None of the lesions had signal in Doppler mode. One lesion was not detected due to the thick overlying bone.

MR study was performed on the axial and coronal T1, T2 weighted images (WI), and pre- and post-contrast T1WI. Three isolated lesions were detected in the mandible. Lesions showed low to intermediate signal intensity on T1WI with moderate peripheral enhancement (Figs. 5A-C). On T2WI, the lesions had high signal intensity with internal homogeneity (Fig. 5D). There was an expansile, well defined, and hyper intense lesion in the right maxillary sinus with heterogeneous signal on T2WI due to high protein content. Incidentally, a mucous retention pseudocyst in the left maxillary sinus was found with a homogenous intermediate signal on T1WI without peripheral enhancement and high signal intensity on T2WI (Figs. 5E and F).

On histopathologic examination, 4 lesions reported to be of parakeratinized KCOT and the lesion in the right maxillary sinus was orthokeratinized odontogenic lesion (Fig. 6).

KCOT represents from 3 to 15% of all odontogenic lesions and appears in 65-75% of cases of the syndrome. This lesion has been of interest due to its biological aggressiveness and high reported rate of recurrence.9 On radiographs, KCOTs appear as uni/multilocular radiolucent lesions that may have a smooth or scalloped border.3,6 Cortical expansion and thinning and rarely a hazy lumen have been reported in the previous reports.6 The lesions sometimes occur around an impacted tooth.4

Nevertheless, few studies have assessed ultrasonographic appearances of KCOTs. Lauria et al10 reported that KOTs were hypoechogenic in 7 of 9 cases because of their dense and thick content, and 2 other lesions showed solid content in their study on ultrasonographic evaluation of bone lesions of the jaw. In 2010, Bagewadi et al11 stated a homogenous hypoechoic internal echo pattern for this lesion. In 2009, Sumer et al12 evaluated 4 odontogenic keratocysts by ultrasonography, and for the first time, by Doppler mode. Three lesions had complex, dense echo without internal vascularization which was consistent with the findings by Lauria et al. The other lesion was not detected due to the thick vestibular bone. In the present study, we also used Doppler mode to check internal vascularization. Three lesions were hypoechoic without Doppler signal similar to the previous studies. The lesion in the right maxillary sinus which was associated with an impacted tooth had a mixed pattern in US study.

MRI of KCOT shows various signal intensities. In 2002, Hisatomi et al7 reported an intermediate-to-high signal intensity on T1WI (T1 weighted image) and heterogeneous low-high signal intensity on T2WI and stated that these signal intensities on MRI might be suggestive of KCOT. Minami et al6 in 1996 showed that odontogenic keratocysts had intermediate or high signal intensity on T1WI and intermediate signal intensity on T2WI. In the present case, all lesions had high signal intensity on T2WI except for the right maxillary lesion that showed heterogeneous high signal intensity on T2WI. Sometimes the lumen of KCOT contains a large quantity of keratin. If the lesion was secondarily infected, cholesterol and hyaline bodies might be found. Therefore, the signal intensity on T1/T2WI might reflect these contents.

In 2005, the World Health Organization (WHO) classified the parakeratinized odontogenic tumor as KCOT and stated that orthokeratinized cystic lesions (OOC) were separate entity.13,14

KCOT is the lesion that occurs in Gorlin's syndrome.13,15,16 Bolbaran reported a case of orthokeratized type in basal cell nevoid syndrome,15 however KCOTs associated with syndromes often were of parakeratinized type and had a much higher recurrence rate compared with the isolated ones.2,13 McDonald-Jankowski reported that orthokeratinized odontogenic lesions occurred with an unerupted tooth significantly more than parakeratinized ones.13,17 This may indicate a different pathogenesis for lesions associated with impacted teeth and probably a different keratin content which is reflected in MR and US studies.

In this case, the pericoronal lesion in the right maxillary sinus revealed the different echo pattern compared with others, reported to be an OOC. It seems that pericoronal lesions may have different internal keratin density which is responsible for its heterogenous appearance in MR and mixed echo pattern in US studies. Unfortunately, the previous studies did not indicate whether KCOTs were related to the impacted teeth or not.

Crowley et al stated the recurrence rates of KCOTs (42.6%) and OOCs (2.2%).18 Therefore, it is also important from the treatment aspect, since the parakeratinized lesions had more aggressive behavior to decrease the recurrence rate.13 However, the rate of recurrence in syndrome associated lesions is higher than the isolated ones.9

In conclusion, KCOTs might represent various imaging features, especially using sophisticated modalities such as MR and US studies. These features might predict the aggressiveness of KCOTs which was the most helpful planning a surgical and follow up protocol. In addition, our US findings were compatible with the findings in CT and MR studies. Therefore, US study provides to evaluate the size and content of maxillofacial lesions. It is important to establish the diagnosis as soon as possible in syndrome-related KCOTs due to the susceptibility of these patients to fatal neoplasms.