Radiographic Diagnosis Of Pathology Affecting The Jaws Question And Answers

Radiographic Diagnosis Of Pathology Affecting The Jaws

Question 1. describe radiological differential diagnosis for ameloblastoma, central giant cell granuloma, odontogenic myxoma and central hemangioma.
Answer.

Radiological Aifferential Diagnosis for Ameloblastoma

Small and Unilocular ameloblastoma

• Small unilocular ameloblastomas that are located around the crown of an unerupted tooth often cannot be differentiated from a dentigerous cyst.
• Residual cyst: History of extraction of tooth is present.
• Lateral periodontal cyst: Seen in incisor, canine and premolar area in the maxilla, ameloblastoma occurs more in the mandibular molar area.
• Giant cell granuloma: Seen more often in areas anterior to the molars, younger age group and have more granular and ill-defied septae.
• Traumatic bone cyst: This occurs in the mid twenties, whereas ameloblastoma is more common in the 3rd and 4th decades.

Multilocular Ameloblastoma

• Odontogenic keratocyst: It contains curved septae but tends to grow along the bone without marked expansion.
• Odontogenic myxoma: There is history of missing tooth and has a presence of septa that divide the image into muchfier coarse than those in ameloblastoma. Myxoma has one or two thin sharp, straight septa which are characteristic of it. Myxomas are not expansile and tend to grow along the bone.
• Ossifying firoma: The septa are usually wide, granular and ill-defied. Small irregular trabeculae are seen.
• Radiological Differential Diagnosis for central Giant cell Granuloma
• Early stage (Radiolucent appearance)
• Giant cell lesions of hyperparathyroidism: Here there is overall radiolucency, the serum alkaline phosphatase and serum calcium levels are raised, with a decrease in serum phosphate levels.
• Osteoporosis: It may be confused with Paget’s disease in the early stage, but if the area is pathologically enlarged with straight linear trabeculae seen aligned parallel to the long axis of the affcted bone, osteoporosis is ruled out.
• Osteomalacia: Pseudofractures are common in this case. The serum calcium and serum phosphorous levels are decreased in this case, whereas they are normal in Paget‘s disease.
• Multiple myeloma: There is a painful enlargement of the jaws and shows typical radiolucent punched out lesions on the skull radiograph.

Read And Learn More: Oral Radiology Question And Answers

Second Stage (Mixed Radiolucent Radiopaque Appearance)

• Osteogenic sarcoma: This occurs in the younger age group, and shows a variety of radiographic appearances such as, sunburst and Codman’s triangle.
• Cementifying and ossifying firoma: This is also seen in the younger age group, and shows well-defied margins in contrast to the diffuse border of the lesions of Paget’s disease.
• Fibrous dysplasia: Seen in younger patients, Paget’s disease spreads more diffusely, seen bilaterally and has linear trabeculae and a cotton-wool appearance which is distinctive. In fibrous dysplasia, the size of maxillary sinus is reduced, whereas in Paget’s disease the air space is not reduced.
• Osteoblastic metastatic carcinoma: There will be history of a primary tumor.
• Ossifying subperiosteal hematoma: It is seen in patients younger than 15 years of age, and the patient usually gives history of recent trauma.
• Chondroma and chondrosarcoma: There is complaint of intense pain which is usually not there in the case of Paget’s disease.

Advanced Stage (Purely Radiopaque appearance)

• Florid osseous dysplasia: Hypercementosis is present, but it is only confined to the jaw bones, in localized area only. In case of Paget’s disease when the jaw bones are involved, it affects all of the jaw. This may have a cotton-wool pattern, but these lesions are centered above the inferior alveolar canal and commonly have a radiolucent capsule.
• Osteosclerosis: The lesion is usually small and confined to the jaw bones.
• Tori: The lesion is usually small and confined to the jaw bones.
• Osteoma: The lesion is usually small and confined to the jaw bones.

Radiological Differential Diagnosis for Odontogenic Myxoma

• Central giant cell granuloma: It has a preferred anterior location in the mandible.
• Ameloblastoma: This occurs in older patients.
• Cherubism: This occurs in the younger age group and has a bilateral involvement.
• Metastatic carcinoma: In the older age group and there wil be presence of the primary tumor.
• Aneurysmal bone cyst: This is tender and painful.
• Osteogenic sarcoma: This also has a speculated appearance but the outer cortex is lost in osteogenic sarcoma which is not so in odontogenic myxoma.

Radiological Differential Diagnosis for Central Hemangioma

• Central giant cell granuloma: This crosses the midline.
• Giant cell lesions of hyperparathyroidism: Maybe differentiated by biochemical investigations.
• Aneurysmal bone cyst: Hemangioma will show profuse hemorrhage, if aspirated.
• Ameloblastic firoma: No local gingival bleeding or pumping action of the involved tooth seen.
• Odontogenic myxoma: Shows a typical tennis racket appearance.
• Cherubism: Usually seen in children, with a typical facial appearance and is bilateral.

Question 2. Write short note on multiple punched out radiolucencies of jaw.
Answer. Following are the multiple punched-out radiolucencies of jaw:

• Multiple myeloma
• Eosinophilic granuloma

Multiple Myeloma

• Occurs during 4th to 7th decades of life.
• Male predilection is present with male to female ratio of4:1.
• Mandible is more commonly affected.
• Patient complaints of pain as well as swelling in jaw along with numbness of jaw.
• There is presence of swelling intraorally which is round in shape, bluish red in color and has tendency to ulcerate. While palpating the swelling, it is tender and egg, shell crackling is also appreciated.
• Lesion appears as small and rounded with discrete radiolucency which has punched out appearance. Multiple areas of bone destruction are seen in area of generalized radiolucency.

Eosinophilic Granuloma

• Occur in alder children and young age group.
• Male predilection is present.
• Posterior region of mandible is commonly affected.
• Gingivitis is present and there is also presence of bleeding gingiva. Pain is present and at times ulceration is also seen.
• Mobility of teeth is present along with destruction of alveolar bone.
• In jaw the lesion shows discrete borders which are seldom hyperosteotic and thus show punched out appearance. Lesions are elliptical or circular in shape.

Question 3. Give differential diagnosis of mixed radiopaque and radiolucent lesions of jaws.
Answer.

Mixed Radiopaque and Radiolucent Lesions of Jaws

• Intermediate stage of Paget’s disease
• Fibrous dysplasia
• Osteoid osteoma
• Chronic osteomyelitis
• Osteoradionecrosis
• Cemento-ssifying firoma
• Calcified epithelial odontogenic tumor (CEOT)
• Osteogenic sarcoma
• Chondroma
• Chondrosarcoma
• Central hemangioma
• Ossifying subperiosteal hematoma

Mixed Radio-paque and Radiolucent Lesions Associated with teeth

cemento-ossifying Fibroma

• Osteoblastoma: Histology helps in establishing diagnosis.
• Osteosarcoma: Osteosarcoma is a malignant tumor which shows malignant characteristics such as invasion of tumor cells in sof tissue, destruction of cortices while cemento ossifying firoma is benign in nature.
• Osteoid osteoma: More common in men at 3rd to 4th decade while cemento-ossifying firoma is common in women of same age group. Osteoid osteoma leads to pain during night while cemento-ossifying firoma is asymptomatic.
• Calcifying epithelial odontogenic tumor (CEOT): Most common site of occurrence is posterior body and ramus of mandible while most common site of occurrence for cemento-ssifying firoma is mandibular premolar-molar region.
• Chondrosarcoma: In chondrosarcoma borders are ill defied with formation of periosteal bone while in cemento ossifying firoma borders are well defied.
• Periapical cemental dysplasia: In periapical cemental dysplasia occurance is in older age group as compared to periapical cemental dysplasia. Periapical cemental dysplasia occur in mandibular incisor lesion while cemento ossifying firoma occur in premolar-molar region.
• Fibrous dysplasia: It has equal sex predilection while cemento ossifying firoma is more common in females. Border of lesion in firous dysplasia is ill-defied while in Paget’s disease borders are well defied.
• Paget’s disease: Paget’s disease show cottn-wool appearance while no such appearance is seen in cemento-ossifying firoma.
• Benign cementoblastoma: In benign cementoblastoma tumor is attched to the root and shows root resorption while in cemento-ossifying firoma, tumor is not attched to root. Benign cemento blastoma is associated with pain while cemento-ossifying firoma is asymptomatic.
• Juvenile ossifying firoma: Juvenile ossifying firoma is seen in 1st to 2nd decades while cemento-ossifying firoma is seen in 3rd to 4th decades. In juvenile-ossifying firoma maxilla is commonly affected while in cemento-ossifying firoma mandible is commonly affected. Radiographic appearance of both lesions is similar, diagnosis is made histologically.

Fibrous dysplasia

• Osteoblastic metastatic carcinoma: Osteoblastic carcinoma does not reveal monotonous pattern while fibrous dysplasia show monotonous pattrn.
• Osteosarcoma: Osteosarcoma shows Codman’s triangle, sunburst pattrn while firous dysplasia shows granular pattern.
• Chondrosarcoma: Chondrosarcoma is painful while in firous dysplasia, frank pain is there. Fibrous dysplasia is seen in younger age group while chondrosarcoma is seen in older age group.
• Cemento-ossifying fibroma:
  • Cemento-ossifying fibroma has predilection for mandible while fibrous dysplasia has predilection for maxilla.
  • Shape of cemento-ossifying fibroma is rounded while of fibrous dysplasia is rectangular.
  • Margins in cemento-ossifying fibroma are sharply defied while in fibrous dysplasia, they are indistinct.
  • Cemento-ossifying fibroma is seen in young people while fibrous dysplasia is seen in older persons.
• Paget’s disease: Serum alkaline levels are raised in paget’s disease, while they are within normal range in fibrous dysplasia.

Paget’s disease

• Osteoblastic metastatic carcinoma: Osteoblastic metastatic carcinoma shows history of primary tumor while Paget’s disease does not had such history.
• Osteosarcoma: Osteosarcoma occurs in younger age group while Paget’s disease occur in middle age group. Osteosarcoma shows radiographic appearance such as sun ray appearance and codman’s triangle.
• Chondrosarcoma: One of the common symptom of chondrosarcoma is pain while pain is absent in Paget’s disease.
• Cemento-ossifying-fibroma: Cemento-ossifying fibroma occurs in younger age group while paget’s disease occur in 40 years of age. Cemento-ossifying firoma show well defined margins while Paget’s disease shows diffuse margins.
• Fibrous dysplasia: Fibrous dysplasia occurs in younger age group while Paget’s disease is seen during 40 years of age. Paget’s disease resemble cottn wool-appearance while firous dysplasia shows motted appearance. In firous dysplasia, maxillary sinus is reduced while in paget’s disease air space is not reduced.
• Ossifying subperiosteal hematoma: Ossifying subperiosteal hematoma is seen in younger age, i.e. 15 years and there is also history of recent trauma.

Osteosarcoma

• Metastatic carcinoma: In metastatic carcinoma, history of primary tumor is evident while no such history is seen in osteosarcoma.
• Chondrosarcoma: Chondrosarcoma occurs in older age group and there is predilection for maxilla while osteosarcoma occur in middle age group and predilection for maxilla and mandible is equal.
• Ossifying firoma: Internal structure is uniform in ossifying firoma, while it is non-uniform in osteosarcoma.
• Fibrous dysplasia: Lesions are more demarcated and have uniform appearance as compared to osteosarcoma.
• Ossifying subperiosteal hematoma: Patient will give history of recent trauma in ossifying subperiosteal hematoma, while it is not so in osteosarcoma.

Chondrosarcoma

• Osteosarcoma: Chondrosarcomareveals typicalcalcifiations in radiograph which are absent in osteosarcoma.
• Fibrous dysplasia: In radiograph, periphery of fibrous dysplasia is well defied as compared to chondrosarcoma. In chondrosarcoma, widening of PDL space is seen while in firous dysplasia thinning of PDL is seen.

Osteoid osteoma

• Osteoblastoma: Osteoid osteoma is more painful as compared to osteoblastoma.
• Ossifying firoma: In ossifying firoma, root resorption is present while in ossifying firoma root resorption is absent.
• Fibrous dysplasia: In firous dysplasia, predilected site is maxilla while in osteoid osteoma slight predilection of mandible is present.

Question 4. Write short note on multilocular lesions of jaws.
or
Write short note on multilocular radiolucency.
Answer. Multilocularity is due to presence of bony septa in the lesion.

Multilocular Lesions of Jaw

• Ameloblastoma
• Ameloblastic firoma
• Ameloblastic firo-odontoma
• Odontogenic myxoma
• Calcifid epithelial odontogenic tumor
• Squamous odontogenic tumor
• Central giant cell granuloma
• Odontogenic keratocyst
• Aneurysmal bone cyst
• Fibrous dysplasia
• Cherubism
• Metastatic tumor of jaw
• Burkitts lymphoma
• Brown tumor.

Ameloblastoma

It shows multilocular cyst like appearance with multiple cystic cavities and thin septae which separates cystic cavities.

Odontogenic Myxoma

It is multilocular with mixed radiopaque-radiolucent pattern. Septas are present which are straight and thin or curved and coarse septas can also be seen with two or three straight septae. The tumor show tennis-racket like or step-ladder pattrn.

Calcifying Epithelial odontogenic tumor

As the lesion matures, it show multilocularity, it shows honey, comb pattrn with numerous scattred radiopaque foci which are close to crown of impacted tooth. At times, small thin and opaque trabeculae cross radiolucency in multiple directions which provides it snow-driven appearance.

Central Giant cell Granuloma

In central giant cell granuloma, a stubble granular pattrn of calcifiation can be seen which are organized in wispy septae. At times, septa are bettr defied at right angles to periphery and divide internal aspect in compartments which provide it honey comb appearance.

Odontogenic Keratocyst

Radiologically, it shows aggressive growth with undulating borders, cloudy interiors and internal septas which give it multilocular appearance.

Aneurysmal Bone cyst

It is an expandable osteolytic processs. As cyst increases in size it leads to expansion of buccal and lingual plates. Septae may be seen within the lesion which gives it multilocular appearance.

Cherubism

There is a presence of radiolucency with fie granular bone and wispy trabeculae forming multilocular pattrn.

Question 5. Write short note on unilocular radiolucent lesions of jaw bone.
Answer. Following are the unilocular radiolucent lesions of jaw bone:

• Radicular cyst
• Residual cyst
• Dentigerous cyst
• Lateral periodontal cyst
• Nasopalatine duct cyst
• Calcifying epithelial odontogenic tumor
• Adenomatoid odontogenic cyst
• Primary bone tumors
• Secondary metastasis tumor
• Eosinophilic granuloma
• Multiple myeloma
• Fibrocemento-osseous lesion
• Stafne’s cyst.

Radicular cyst

It appears as a well-defied unilocular radiolucency with thin hyperostotic borders. The cyst is associated with a non-vital tooth.

Residual cyst

It has a unilocular appearance with thin radiopaque margins. It is round or ovoid in shape and is well circumscribed.

Dentigerous cyst

Usually, the dentigerous cyst is unilocular with wellcircumscribed margins. Radiolucency of the cyst is well defied.

Adenomatoid odontogenic cyst

Radiolucency in adenomatoid odontogenic cyst is well demarcated and has association with the impacted tooth.

Stafne’s cyst

It is a unilocular round radiolucency which is approximately 1 to 3 cm in diameter. At times, Stafne’s defect is bilateral too.

Question 6. Discuss multilocular radiolucencies occurring at the angle of mandible.
Answer. Following are the multilocular radiolucencies occurring at the angle of mandible:

• Odontogenic keratocyst
• Ameloblastoma
• Ameloblastic firoma
• Odontogenic myxoma
• Cherubism
• Aneurysmal bone cyst
• Metastatic tumor of jaw
• Fibrous dysplasia.

Odontogenic Keratocyst

Its occurrence is more than 50% on angle of mandible. Undulating borders of the tumor with cloudy internal appearance is suggestive of multilocularity. It shows mediolateral expansion.

Margins of lesion are hyperostotic. In some of the subjects, it shows perforation ofbuccal and lingual cortical plates. Inferior alveolar canal undergo downward displacement. As there is enlargement oflesion the unerupted teeth get deflcted in region of angle of mandible.

Ameloblastoma

It is multilocular with presence of septa in the lesion. Arrangement and number of septa provides it the honey-comb appearance or soap-bubble appearance. Outline of tumor is smooth, well–defied, well corticated and scalloped. As there is expansion in the tumor bony compartments get coalesce and fuses. As cortical plates get thinned on expansion it is known as eggshell of bone.

Ameloblastic Fibroma

Associated with the premolar-molar area of the mandible. The lesion appears as pericoronal radiolucency. The lesion is associated with missing or unerupted tooth. Margins of the lesion are well defied with sclerotic borders. It also shows buccal and lingual expansion of jaw with intact buccal plates. Teeth get deflcted from normal path of eruption.

Odontogenic Myxoma

Lesion is well defied. Compartments of the lesion can be angular and are separated by straight septa. Lesion can be scalloped between the roots of adjacent teeth. It shows honey, comb or Tennis-racket appearance.

Cherubism

The lesion occurs at angle of mandible bilaterally. Lesion shows cyst-like radiolucency. It progresses as bony destruction at the angle of mandible and later on the expansion of lesion occur in ramus. Lesion appears as classic multilocular radiolucency because of internal radiopaque septa. Margins of lesion are well defined, well corticated as well as smooth. Buccal and lingual cortical plates also show expansion. Premature exfoliation of deciduous teeth is also seen.

Fibrous dysplasia

In its early stage, the lesion is radiolucent with ill-defined borders. In majority of cases, bony septa are apparent and appear as multilocular defect. Margins of the lesion are well defined and can blend with surrounding normal bone. Margins are surrounded by a band of increased density which gives granular appearance. Resorption of roots is also seen.

Metastatic Tumor of Jaw

Lesion is seen at angle or in complete mandible too. It is bilateral. Bone destructionshows irregular margins along with some bony islands present in radiolucent areas. Margins are ill-defied and are invasive. There is presence of punched-out radiolucency.

Question 7. Enumerate and differentiate various radiopaque lesions of the jaws.
Answer.

Radiopaque Lesions of Jaws

• Abnormalities of teeth
  • Unerupted and misplaced teeth including supernumeraries
  • Odontomas, i.e. compound and complex
  • Root remnants
  • Hypercementosis
• Conditions which affect the bone
  • Developmental: Exostosis including tori i.e. either mandibular or palatal.
  • Inflmmatory
    • Low grade chronic infection: Sclerosing osteitis
    • Osteomyelitis: Sequestra, involucrum formation
  • Tumors odontogenic (Late stages)
    • Calcifying epithelial odontogenic tumor
    • Adenomatoid odontogenic tumor
    • Calcifying odontogenic cyst
  • Non-odontogenic tumor
    • Benign: Osteoma, chondroma
    • Malignant: Osteosarcoma, Osteogenic secondary metastasis
  • Fibro-cemento-osseous lesions
    • Fibrous dysplasia
    • Periapical cemental dysplasia
    • Gigantiform cementoma
    • Benign cementoblastoma
    • Cemento-ossifying firoma
  • Others
    • Paget’s disease
    • Osteopetrosis
• Superimposed soft tissue calcifications
  • Salivary calculi
  • Calcified lymph node
  • Calcified vessels
  • Phleboliths
  • Calcified acne scars
• Foreign bodies
  • Intrabony
  • Within the soft tissue
  • On or overlying the skin

Differential Diagnosis of Radiopaque Lesions of Jaws

Odontomas i.e. Compound and Complex

• Difference between compound and complex type: Compound consists of more than one fragment and is more commonly seen in maxillary canine region while complex has one solid mass and is commonly seen in mandibular molar region.
• Cementifying or Ossifying firoma: Association of odontoma is with unerupted molar teeth and is more radiopaque as compared to firoma. It also occurs at younger age as compared to firoma.
• Adenomatoid odontogenic tumor: It is rarely as opaque as complex type and is seen in association with the maxillary canines.
• Periapical cemental dysplasia: It is smaller than complex type and is limited to mandibular anterior region. Periapical cemental dysplasia are multiple lesions and has wider, uneven sclerotic border while odontomas have well defied cortical border and usually the sof tissue capsule is more uniform and is bettr defied.
• Calcifying epithelial odontogenic tumor: It is rare, less opaque and develops in midline.
• Fibrous dysplasia: It is mottled or have smoky pattern with poorly defied borders.

Hypercementosis

• Any radiopaque structure which is seen in the vicinity of the root like enostosis, mature cemental dysplasia.
• Multirooted teeth and dilacerated root
• Main differentiating characteristic is presence of periodontal membrane space around hypercementosis.

Exostosis Including Tori i.e. either Palatal or Mandibular

It can be diffrentiated from periapical radiopacity by taking another radiograph with diffrent horizontal angulation of the central ray.

Condensing osteitis

• Hypercementosis: It is seen as a integral part of malformed root and associated with an intact lamina dura and periodontal ligament space. Associated tooth is vital.
• Periapical cemental dysplasia: It is associated with vital teeth and the lesion is separated from the surrounding bone by a radiolucent border.
• Osteosclerosis: It is associated with an edentulous area.

Calcifying Epithelial odontogenic Tumor

• Adenomatoid odontogenic tumor: This is common in anterior maxilla as compared to calcifying epithelial odontogenic tumor which is common in mandibular molar – premolar region.
• Calcifying odontogenic cyst: On aspiration viscous granular yellow colored flid is seen.
• Central odontogenic firoma: Histologically, firoblasts are prominent and abundant.

Adenomatoid Odontogenic Tumor

• Calcifying odontogenic cyst: It is diffilt to diffrentiate from extrafollicular type of adenomatoid odontogenic tumor. It occurs in older age group mainly in premolar area.
• Calcifying epithelial odontogenic tumor: It is found commonly in mandibular posterior region.

Osteoma

• Solid odontome: It shows presence of sof tissue capsule.
• Fibrous dysplasia: No clearly defied borders are present. It does not reveal same homogeneous density as in osteoma.
• Osteosarcoma: There is bony enlargement along with typical sunray appearance.
• Ossifying firoma: Presence ofbony enlargement with dense radiopaque mass.

Chondroma

• Osteogenic sarcoma: It shows typical sunray appearance.
• Fibrous dysplasia: This can be diffrentiated histologically and radiographically it has ground-glass appearance.
• Osteoblastic metastatic carcinoma: There will be presence of primary tumor.
• From radiographic point of view it is not possible to identify chondroma inthe jaws. Anarea ofbone destruction without the characteristics of the cyst, occurring in region of condyle or coronoid process is considered as possible of being cartilaginous in origin.

Gigantiform cementoma

• Paget’s disease: Radiolucent capsule is absent. There are increased serum alkaline phosphatase levels. This affcts nearly all bones of skeleton. It affcts entire mandible while gigantiform cementoma is centered above inferior alveolar canal.
• Osteopetrosis: There is profuse thickening of skull base or calvarium and diffuse bone radiopacities. It will lead to enlargement of bone but this will not happen in gigantiform cementoma.
• Chronic sclerosing osteomyelitis: Region of cementum may appear similar o that of sequestrum, CT imaging aids in diffrentiation.

Benign cementoblastoma

• Periapical cemental dysplasia: No expansion of jaws, females are more commonly affcted and radiolucent band is not uniform in fist molar region, cementoblastoma has a more rounded shape than cemental dysplasia.
• Periapical sclerosing osteitis: It does not have sof tissue capsule.
• Hypercementosis: It does not have sof tissue capsule and is surrounded by periodontal ligament space which is much thinner than sof tissue capsule of cementoblastoma. There is no root resorption or jaw expansion.

Paget’s disease

• Florid osseous dysplasia: Hypercementosis is present but it is only confied to the jaw bones. In Paget’s disease when jaw bones are involved, it affcts complete jaw. This may have cotton wool pattrn , but the lesions are centered above inferior alveolar canal and commonly have radiolucent capsule.
• Tori: Lesion is small and is confied to jaw bones.
• Osteoma: Lesion is small and is confied to jaw bones.

Osteopetrosis

• Polyostotic firous dysplasia: It involves part of a bone rather than complete bone.
• Paget’s disease: It involves skull, pelvis, vertebrae, femur, maxilla and mandible. There is marked elevation of serum alkaline phosphatase levels.

Salivary calculi

• Phleboliths: There will be no sialadenitis and these are more or less rounded and consist of laminations or central dark areas.
• Calcified submandibular lymph node: If there is presence of pain, it is suggestive of sialolith. Calcified lymph node appears to be cauliflower shaped.

Phleboliths

Sialolith: It occur singly, if multiple sialoliths are present , they are oriented in a single line while phleboliths are multiple and have more random clustered distribution and is associated with vascular lesion.

Calcified Lymph Node

• Sialoliths: It is painful and have smooth outline. Patient may have symptoms related to submandibular salivary gland. Sialography aid in diffrentiation.
• Phlebolith: These are smaller and have concentric radiopaque and radiolucent rings, its shape may mimic a portion of blood vessel.