Clinicopathological study of radicular cysts with actinomycosis

Abstract

Background/purpose: Actinomycosis is sometimes associated with a radicular cyst (RC). This retrospective study evaluated the clinical and histopathological features of 6 RCs with actinomycosis (AM/RCs).

Materials and methods: The demographic data and clinicopathological features of 6 AM/RCs were collected and analyzed.

Results: The 6 AM/RCs were taken from 2 male and 4 female patients, and 3 were found in the maxilla and the other 3 in the mandible. The involved teeth included maxillary or mandibular incisors (2 cases) and maxillary or mandibular first and second molars (4 cases). The most common symptom was pain (5 cases) and the more frequent signs were sinus tract and pus discharge (4 cases). Microscopically, the actinomycotic colony presented as a mass with filamentous bacteria arranging in a sun-ray pattern at the periphery. The mean actinomycotic colony number was 7.7 ± 6.6 colonies per slide. Due to the severe inflammation in all 6 AM/RCs, the stratified squamous epithelial lining was completely abolished in 2 cases and partially destroyed in 4 cases with the residual epithelial lining varying from approximately 10%-50%.

Conclusion: Our results indicate that pain is the most common symptom and sinus tract and pus discharge are the two frequent signs of our 6 AM/RCs. The stratified squamous epithelial lining was either completely abolished (2 cases) or partially destroyed (4 cases) in 6 AM/RCs. Thus, if the endodontically-treated tooth shows a recurrent sinus tract and poor response to repeated conventional root canal treatments, periradicular actinomycotic infection should be highly suspected.

Keywords: Actinomycosis; Clinical feature; Histopathological feature; Radicular cyst.

Figure 1

Histopathological features of actinomycotic colonies. (A) Low-power microphotograph showing several actinomycotic colonies in the lumen of a radicular cyst. The actinomycotic colonies revealed variations in the color between the center and periphery of each colony. (B) High-power microphotograph of the peripheral area of an actinomycotic colony exhibiting deep blue filamentous bacteria arranging in a characteristic sun-ray pattern. (C) Low-power microphotograph demonstrating an actinomycotic colony surrounded by aggregates of red blood cells in the lumen of a radicular cyst (left half) and the fibrous cystic wall of a radicular cyst with a severe lymphoplasma cell infiltrate but without an epithelial lining (right half). (D) High-power microphotograph of an actinomycotic colony showing the homogenous and slightly basophilic central part and the blue filamentous bacteria arranging in a specific sun-ray pattern at the peripheral part. (Hematoxylin and eosin stain; original magnification; A, 4×; B, 40×; C, 10×; D, 40×).

Figure 2

Histopathological features of radicular cysts with actinomycosis. (A) Low-power microphotograph exhibiting a well-encapsulated fibrous cystic wall of a radicular cyst. The outer one quarter of the cystic wall was composed of dense collagenous fibrous tissue with a very mild lymphoplasma cell infiltrate but the inner three quarters of the cystic wall was infiltrated by a sheet of lymphoplasma cells with foci of hemorrhage. No lining epithelium was found on the inner surface of the radicular cyst. (B) High-power microphotograph showing a severe lymphoplasma cell infiltrate in the fibrous cystic wall of a radicular cyst. (C) Low-power microphotograph showing a severely-inflamed radicular cyst with a stratified squamous epithelial lining (arrows) and an actinomycotic colony in the lumen of the radicular cyst (near right upper corner). (D, E and F) Aggregates of foamy histiocytes (D), cholesterol clefts (E), and scattered hemosiderin-laden macrophages (arrows) were discovered in the severely-inflamed fibrous cystic wall of a radicular cyst. (Hematoxylin and eosin stain; original magnification; A, 4×; B, 20×; C, 4×; D, E, and F, 40×).