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A case of mandibular cystic adenoid carcinoma was observed in a 49-year-old man. After slow progression, the diagnosis was directed to mandibular pseudocystic tumor. The treatment was enucleoresection. Histological findings in this exceptionnal lesion led to a discussion of the radioclinical diagnosis and etiopathogenic features of adenoide cystic carcinoma. The origin of this tumor is hypothesized to be heterotopic salivary inclusion although no histologicaly proof can be provided.

A malignant xanthogranuloma located in the mandible presented as a tumefaction of the alveolar crest with labiomental hypoaesthesia in a 52-years-old woman. The patient was treated with combined chemoradiotherapy and remained in complete remission for 14 years. Epidemiologic features (age, sex, race) of this tumour are discussed in light of the 24 cases reported in the literature. Histology features and possible treatment protocols as well as observed results are discussed. Five-year survival rate in malignant cervicofacial xanthogranulomas is estimated at 48%.

An adenomatoid odontogenic tumor located in the mandible was studied in a 28 year-old woman. The clinical, histological and ultrastructural characteristics of this rare tumor are described out and the histogenesis is discussed.

One case of aggressive intramandibular epithelial tumor is presented. This tumor demonstrated an unusual pattern with areas of follicular ameloblastoma together with undifferentiated trabeculae or lobules composed of basophilic cells and of clear glycogenic-rich cells. The odontogenic nature of this tumour and its analogies with common ameloblastoma were demonstrated by electron microscopy, immunohistoenzymology and immunohistochemistry. The signification of such a neoplasm is discussed.

A rare case of primary central squamous-cell carcinoma of the mandible is reported. Etiology, pathogenesis, clinical features and differential diagnosis are discussed.

The rare case reported here was a mandibular metastasis of a malignant melanoma located in the nape of the neck and surgically removed. 4 years later, occurred a fibrosarcomatous mandibular tumour without local recurrence. The metastatic nature of this tumour was difficult to prove by means of immunohistochemical and ultrastructural methods. This case illustrated the eventuality of a desmoplastic change in metastasis of a common malignant melanoma. The histogenesis of this rare type of melanoma was discussed.

A case of post-traumatic desmoid tumor of the mandible is reported in a 4-year old girl. This tumor was considered typical clinically and by light microscopy. Four years later, the patient was symptomless, without evidence of recurrence. Histoenzymology showed a high level of leucine aminopeptidase activity. On electron microscopy, a part from a few primitive mesenchymal cells, abnormal fibroblasts represented the principal cellular component. These cells showed evidence of intracytoplasmic collagen fibers synthesis and of myoid differentiation (numerous filaments and endocytosis vacuoles). Myofibroblasts, with a microfibrillary network showing areas of dense osmiophilic condensation in the vicinity of cell membrane were also present. This atypical ultrastructural feature suggests, in this case, the non-neoplastic nature of this lesion. It seems to reflect an abnormal reaction to a traumatic aggression, characterized by proliferation of myofibroblasts (which normally disappear in the late stages of healing) and to have, thus, the signification of pathologic scar.

Histoenzymologic and ultrastructural examinations were conducted on a doubly located calcified odontogenic epithelial tumor. The cells of the tumor, developing in both the maxilla and mandible, differed from those of the common ameloblastoma, being all of the malpighian type without any secretory polarity. Furthermore, optical and electronic microscopy showed evidence of marked alkaline phosphatases and ATPases activity in their numerous peripheral microvilli. These identical activities to those of the stratum intermedium could suggest the origin of the tumor from these latter cells. But, like the preameloblasts of the dental germ, these tumoral cells produce in their intracytoplasmic vesicles and then excrete into the stroma, a granulofilamentous substance, pseudo-amyloid, which could thus represent an abnormal protein of the enamel matrix. The calcifications, mainly present in this amyloid-like substance, are the expression of an attempt to mineralize this abnormal matrix. Stromal calcifications may result from a sketchy odontogenetic induction, as shown by the intense activity of ATPases and alkaline phosphatases on the fibroblastic cytoplasm membranes.

Three cases of mandibular condyle metastasis of particular interest are reported: -- In two out of the three cases they were detected early enough for the primary tumour to be diagnosed; -- they all presented with articular symptoms; -- all three were treated surgically by excision of the condyles. Diagnosis was confirmed by histological examination, a rare event when mandibular metastasis are concerned, these usually being diagnosed after the primary tumour and then irradiated without histological proof. Primary tumours were respectively bronchial, pancreatic, and mammary.

The ameloblastoma is usually thought to be devoid of any odontogenic capacity. However, the histological, ultrastructural and histoenzymological study of 5 cases demonstrates the fairly high level of differentiation of some ameloblastic cells in such neoplasms. Furthermore, it suggests very early stage of epithelio-conjunctive interaction. The tumours consist, in addition to stellate, squamous, clear and dark epithelial cells, of densely packed peripheral columnar cells similar to the differentiated ameloblasts of the inner epithelium of enamel organ (median nucleus, well-developed rough-surfaced endoplasmic reticulum, mitochondria and lysosomal-vacuolar system located in the distal end of the cells). Besides, the cytoplasmic membrane shows some pocket-like apical invaginations similar to early Tomes processes. On the other hand, similarly to physiological odontogenesis, an abundant amount of granulo-filamentous material is found along the lateral cellular membranes, and the basement membrane. This substance, sometimes, is intermingled with vertical collagenous fibers. In some areas, it is disrupted and cytoplasmic invaginations of epithelial cells, passing through these gaps, are connected with neighbouring mesenchymatous cells. In other respects, despite the lack of any odontoblastic differentiation, the high level of alkaline phosphatase activity found in these cells by means of histo and cytoenzymological technics, looks like that of odontogenic mesenchymal cells. These findings seem to demonstrate the histogenetic unicity of odontogenic tumours. These neoplasms, like the embryonary dental organ, are provided with two types of cells (epithelial and stromal cells). Thus, they are able to induce odontogenesis. But, in ameloblastoma, this power of induction is restricted to a very early stage of odontogenesis.

One case of mesenchymal chondrosarcoma of the mandible is reported in a 18 years-old man. The patient noted swelling and pain and roentgenography showed an osteolytic lesion of the right mandible. Histologically, the feature was obvious with chondroid sheets of round ovoid or elongated cells. Immunohistochemically, numerous cells had positive S-100 protein and vimentin. The electron microscopy showed numerous undifferentiated cells and also fibroblastic and cartilaginous cells. The prognosis of this tumor, usually bad, cannot be yet appreciated in this case (follow-up of only 3 months). The histogenesis of this peculiar variety of chondrosarcoma is discussed.

One case of mandibular mucoepidermoid tumour was observed in a 57 years old man. A progressive swelling of the mandible was shown with an osteolytic feature on roentgenograms. It was treated by hemimandibulectomy. Grossly, the neoplasm was partly cystic. Histologically, it was mainly composed of intermediate clear cells. Its ultrastructure was quite similar to that of mucoepidermoid tumours in other sites. Heterotopic salivary lobules, though lacking in our case, seem to play the major role in the genesis of these tumours.

Three cases of simple ameloblastoma were studied by electron microscopy. The classical ultrastructural features of these tumors are analysed and compared with reports in the literature and the development of the enamel organ. The authors stress the presence of two cell types (light and dark) probably corresponding to different degrees of maturity. One case of cystic ameloblastoma and one of granular cell ameloblastoma are then reported. The nature of the inclusions in this latter tumour is probably mixed: lysomal and secretory, perhaps ameloblastic. Finally, a malignant ameloblastoma is described under electron microscopy, for the first time. Closely related to simple ameloblastomas, it may be distinguished only by the presence of signs of cellular degeneration and numerous mitoses, sometimes abnormal.

A large cyst of mandibular angle was surgically removed in a 20 years-old woman. This cyst was discovered during childhood and was associated with a branchial para-mandibular cyst. It was histologically lined either with a malpighian epithelium with sebaceous islands or with a ciliated cylindrical epithelium. Because of its topography, its association with a branchial cyst and its histological feature quite similar to that of a cyst of thyroglossal duct, this cyst was thought to represent a simplified salivary ectopy composed only of a cystic secretory duct without any salivary parenchyma.