Page 548 - Textbook of Pathology, 6th Edition

532 Odontomas
iv) Basal cell pattern of ameloblastoma is similar to basal
cell carcinoma of the skin. Odontomas are hamartomas that contain both epithelial and
v) Granular cell pattern is characterised by appearance of mesodermal dental tissue components. There are 3 subtypes:
acidophilic granularity in the cytoplasm of tumour cells. i) Complex odontoma is always benign and consists of
Combination of more than one morphologic pattern enamel, dentin and cementum which are not differentiated,
may also be seen. so that the structure of actual tooth is not identifiable.
Tumour cells in ameloblastoma exhibit positive
immunostaining for cytokeratin and laminin as are seen ii) Compound odontoma is also benign and is comprised
in developing tooth. of differentiated dental tissue elements forming a number of
denticles in fibrous tissue.
Odontogenic Adenomatoid Tumour iii) Ameloblastic fibro-odontoma is a lesion that resembles
(Adeno-ameloblastoma) ameloblastic fibroma with odontoma formation.

This is a benign tumour seen more often in females in their Cementomas
2nd decade of life. The tumour is commonly associated with
an unerupted tooth and thus closely resembles dentigerous Cementomas are a variety of benign lesions which are charac-
cyst radiologically. Unlike ameloblastoma, adenomatoid terised by the presence of cementum or cementum-like tissue.
odontogenic tumour is not invasive nor does it recur after Five types of cementomas are described:
enucleation. i) Benign cementoblastoma (true cementoma) is a solitary
lesion of jaw, characterised by features comparable to those
Histologically, the lesion has extensive cyst formations. of osteoid osteoma and osteoblastoma.
The wall of cyst contains scanty fibrous connective tissue
in which are present characteristic tubule-like structures ii) Cementifying fibroma consists of cellular fibrous tissue
composed of epithelial cells and hence the name containing calcified masses of cementum-like tissue.
‘adenomatoid’ (gland-like). iii) Periapical cemental dysplasia (Periapical fibrous
dysplasia) is most common and resembles cementifying
fibroma except that it contains more fibrous tissue as well as
Calcifying Epithelial Odontogenic Tumour
cementum-like tissue.
This is a rare lesion which is locally invasive and recurrent iv) Multiple apical cementomas are found on the apical
SECTION III
like ameloblastoma. It is seen commonly in 4th and 5th region of teeth and detected incidentally in postmenopausal
decades and occurs more commonly in the region of women.
mandible.
v) Gigantiform cementoma is a large lobulated mass of
Histologically, the tumour consists of closely packed cementum-like tissue. Sometimes, there are multiple such
polyhedral epithelial cells having features of nuclear masses in the jaw.
pleomorphism, giant nuclei and rare mitotic figures. The
stroma is often scanty and appears homogeneous and B. MALIGNANT ODONTOGENIC TUMOURS
hyalinised in which small calcified deposits are seen which
are a striking feature of this tumour. Malignant odontogenic tumours are rare.
Systemic Pathology
Odontogenic Myxoma (Myxofibroma) Odontogenic Carcinoma

Odontogenic myxoma is a locally invasive and recurring i) Malignant ameloblastoma is the term used for the
tumour. uncommon metastasising ameloblastoma.
ii) Ameloblastic carcinoma is the term employed for the
Microscopically, it is characterised by abundant mucoid ameloblastic tumour having cytologic features of malignancy
stroma and loose stellate cells in which are seen a few in the primary tumour.
strands of odontogenic epithelium.
iii) Primary intraosseous carcinoma may develop within the jaw
from the rests of odontogenic epithelium.
Ameloblastic Fibroma
iv) Rarely, carcinomas may arise from the odontogenic
This is a benign tumour consisting of epithelial and connec- epithelium lining the odontogenic cysts.
tive tissues derived from odontogenic apparatus. It resembles
ameloblastoma but can be distinguished from it because
ameloblastic fibroma occurs in younger age group (below Odontogenic Sarcomas
20 years) and the clinical behaviour is always benign. The only example of odontogenic sarcoma is a rare
ameloblastic fibrosarcoma. This tumour resembles amelo-
Histologically, it consists of epithelial follicles similar to blastic fibroma but the mesodermal component in it is
those of ameloblastoma, set in a very cellular connective malignant (sarcomatous) whereas the ameloblastic
tissue stroma. epithelium remains differentiated and benign.