Twenty-six patients with hydatid disease of bone were evaluated by means of radiography and conventional tomography. Fourteen patients underwent high resolution computed tomography (CT). In two patients with vertebral disease, magnetic resonance imaging (MRI) examination was also performed. Seventeen patients underwent surgery with histological examination in all. Based on the surgical data and gross examination of the specimen, the radiographic and CT findings have been reviewed to identify the most characteristic radiographic features and to assess the role of CT. Radiographic finding of hydatidosis are rarely typical in bone, and only in a few patients can CT contribute to the diagnosis. On the other hand, the local extension of the lesion both in bone and in soft tissues, which is essential in planning surgery, is always demonstrated well by CT.

Oral malignant melanoma (OMM) is rare, representing less than 0.5% of all oral malignancies. The most affected sites are the palate and the maxillary gingiva. Histological examination is important to establish the diagnosis of any suspicious pigmented lesion in the oral cavity, mainly if a precise clinical diagnosis is not possible. We present one case of OMM that was initially diagnosed as a racial pigmentation elsewhere 2 years earlier. Clinical examination showed multiple macules and nodules located on the hard and soft palate, gingiva and superior alveolar mucosa. These lesions were painless and presented a color variation going from dark blue to black. Histological analysis showed sheets and nests of atypical melanocytes displaying a range of shapes such as plasmacytoid, epithelioid, and round cells, located in the superficial corium extending to the deep tissues. A few tumor cells contained variable amounts of melanin. There was no invasion of blood vessels or nerve fibers. Immunohistochemical analysis revealed that the neoplastic cells were positive for HMB-45, melan-A, S-100 and negative for AE1/AE3, confirming the diagnosis of melanoma. The Ki-67 labeling index was around 25%. The patient refused any treatment and died 11 months later.

Dentigerous cysts (DC) are cystic lesions radiographically represented by a well-defined unilocular radiolucent area involving an impacted tooth crown. We present an unusual radiographic feature of dentigerous cyst related to the impacted mandibular right second molar, in a 16-year-old patient, which suggested an ameloblastoma or odontogenic keratocyst (OKC) because of its multilocular appearance seen on the panoramic radiography. A multi-slice computed tomography (MSCT), however, revealed a unilocular lesion without septations, with an attenuation coefficient from 3.9 to 22.9 HU suggesting a cystic lesion. Due to its extension, a marsupialization was performed together with the histopathological analysis of the fragment removed which suggested a dentigerous cyst. Nine months later, the lesion was reduced in size and then totally excised. The impacted mandibular right second molar was also extracted. Histopathological examination confirmed the diagnosis of a dentigerous cyst. One year later, the panoramic radiography showed a complete mandible bone healing. Large dentigerous cysts can sometimes suggest other more aggressive pathologies. Precise diagnosis is important to avoid mistakes since DC, OKC and ameloblastoma require different treatments. Histological examination is, therefore, essential to establish a definitive diagnosis. In our case, MSCT and the tissue attenuation coefficient analysis contributed to guide the diagnosis and management of the dentigerous cyst.

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