Histological or Microscopic features of Radicular Cyst

Radicular or apical periodontal cyst is an inflammatory odontogenic cyst that develops in the periapical region of a non vital tooth and hence is also called as Root End cyst. The source of epithelium is cell rests of malassez and the proliferation is stimulated by inflammation.

The cyst consists of fibrous connective tissue wall lined by epithelium with a lumen containing fluid and cellular debris. Most periapical cysts grow slowly and do not attain large size. Occasionally similar cyst named lateral periodontal cyst may appear along the lateral aspect of the root. Like periapical cyst this cyst also develop from epithelium cell rests of malassez. The source of inflammation of these cysts is mostly from periodontal disease or pulpal necrosis with spread through lateral foramen or accessory canals extending from the main root canal.

Coming back to radicular cyst, the patient with radicular cyst have no symptoms unless there is acute inflammatory exacerbation. Mild sensitivity and swelling may be seen as the cyst grows larger in size. Movement and mobility of adjacent teeth are seen as the cyst enlarges. These cysts are also known to be associated with deciduous teeth.

Histopathology of radicular cyst or periapical cyst(apical periodontal cyst):

1. The cyst is lined by stratified squamous non keratinized epithelium of variable thickness, and if they are near to Maxillary sinus can be lined with respiratory epithelium.
2. Epithelium shows spongiosis and inflammatory cell infiltration.
3. Cystic lumen is  filled with fluid containing cholesterol crystals.
4. RUSHTON’S BODIES- linear or arc shaped hyaline bodies with variable staining of uncertain origin and unknown significance, but probably of heamatogenous origin, found within lining epithelium.
5. Dystrophic calcification, cholesterol clefts with multinucleated giant cells, red blood cells, and areas of hemosedirin pigmentation may be present in the lumen, wall, or both.
6. Connective tissue capsule adjacent to lining epithelium is delicate with dense inflammatory infiltrate containing lymphocytes variably intermixed with neutrophills, plasma cells, histocytes,and rarely mast cells and eosinophills.
7. The connective tissue capsule may also show cleft like spaces filled with cholesterol that are spindle shaped spaces. The presence of these cholesterol crystals evoke a granulomatous reaction in the connective tissue.
8. Deeper portion of connective tissue capsule is more fibrous with relatively less inflammation.

Characteristic or identification points of Radicular cyst:

1. Non keratinized lining epithelium of variable thickness.
2. Dense inflammation of cystic capsule.
3. Arcading patterns of epithelium.
4. Cholesterol clefts in capsules.

In Radicular Cyst sometimes mucus producing epithelium lining is seen either in maxillary or mandibular locations as a result of metaplastic transformation of epithelial rests of Malassez which are Pluripotential. As reviewed by Gardner in rare cases carcinoma has also been reported to develop from lining epithelium of radicular cysts.

Treatment of Radicular Cyst:

After proper diagnosis of the Cyst, the size and extent of the Radicular cyst is considered and in some cases Root canal treatment can be performed, it should be followed by apicoectomy of the cystic lesion. Most common treatment for a bigger radicular cyst is the extraction of the involved tooth and careful curettage of periapical tissue to make sure that no remnants of the cystic sac are left behind. In case any epithelial remnants or rests are left behind, a residual cyst may develop in this area after the treatment has been performed.

References: Shafer’s Textbook of Oral Pathology, Maji Jose – Oral Histology