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Presented by William Westra, M.D. and prepared by Alex Chang, M.D.
Case 2: 15 year-old boy with a cyst surrounding the crown of an unerupted tooth.
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Week 407: Case 2
15 year-old boy with a cyst surrounding the crown of an unerupted toothimages/1alex/09142009case2image4.jpg
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images/1alex/09142009case2image1.jpgCorrect
Answer: Odontogenic keratocyst, parakeratotic type
Histology: The wall of the cyst is fibrotic and inflamed. The lining of the cyst is comprised of stratified squamous epithelium. In the inflamed areas of the cyst, the squamous lining is hyperplastic. In the uninflamed areas, the squamous lining exhibits: a flat interface with the underlying stroma, uniform thickness (about 6-8 cells), a palisaded basal layer of columnar cells, and a thin parakeratinized cell layer. There is no evidence of ameloblastic transformation.
Discussion: Odontogenic keratocyst (parakeratotic type) is a developmental odontogenic cyst of the jaw that is distinguished from other odontogenic cysts by a distinctive stratified squamous lining that is polarized, uniformly thick, and parakeratinized. OKC is the 4th most common odontogenic cyst behind radicular cyst, dentigerous cyst and paradental cyst. They occur twice as frequently in the mandible as in the maxilla, and have a predilection for the posterior portion of the jaw (specifically, the angle of the mandible and the 3rd molar region of either jaw). OKC may be associated with an unerupted tooth (like a dentigerous cyst), an erupted tooth (like a periapical cyst) or may arise from a non-tooth bearing area of the jaw. Compared to most common odontogenic cysts such as the dentigerous cyst, OKCs are clinically characterized by a strong tendency to recur, necessitating the need for periodic patient follow-up and at times a more aggressive surgical approach. In fact, about 35% of OKCs recur in contrast to a recurrence rate of about 5% for other types of odontogenic cysts. Moreover, approximately 5% of OKCs are associated with the nevoid basal cell carcinoma syndrome. Thus, the diagnosis of OKC, particularly recurrent OKCs, should raise the possibility of this syndrome.
This case illustrates the point that the diagnostic features are often not retained in those regions of the cyst that are inflamed. The presence of squamous hyperplasia and the formation of rete pegs may closely resemble a common inflammatory odontogenic cyst. The entire lesion must be carefully evaluated histologically for the distinctive lining features with special attention to the non-inflamed areas.
In some odontogenic cysts, the squamous lining exhibits prominent orthokeratosis with a granular cell layer. These orthokeratinized odontogenic cysts are sometimes still designated as an orthokeratinized variant of OKC even though they lack the high recurrence rate of the parakeratinized OKC. Furthermore, the orthokeratinized odontogenic cyst lacks the characteristic pallisading of the basal cell layer.
Incorrect
Answer: Odontogenic keratocyst, parakeratotic type
Histology: The wall of the cyst is fibrotic and inflamed. The lining of the cyst is comprised of stratified squamous epithelium. In the inflamed areas of the cyst, the squamous lining is hyperplastic. In the uninflamed areas, the squamous lining exhibits: a flat interface with the underlying stroma, uniform thickness (about 6-8 cells), a palisaded basal layer of columnar cells, and a thin parakeratinized cell layer. There is no evidence of ameloblastic transformation.
Discussion: Odontogenic keratocyst (parakeratotic type) is a developmental odontogenic cyst of the jaw that is distinguished from other odontogenic cysts by a distinctive stratified squamous lining that is polarized, uniformly thick, and parakeratinized. OKC is the 4th most common odontogenic cyst behind radicular cyst, dentigerous cyst and paradental cyst. They occur twice as frequently in the mandible as in the maxilla, and have a predilection for the posterior portion of the jaw (specifically, the angle of the mandible and the 3rd molar region of either jaw). OKC may be associated with an unerupted tooth (like a dentigerous cyst), an erupted tooth (like a periapical cyst) or may arise from a non-tooth bearing area of the jaw. Compared to most common odontogenic cysts such as the dentigerous cyst, OKCs are clinically characterized by a strong tendency to recur, necessitating the need for periodic patient follow-up and at times a more aggressive surgical approach. In fact, about 35% of OKCs recur in contrast to a recurrence rate of about 5% for other types of odontogenic cysts. Moreover, approximately 5% of OKCs are associated with the nevoid basal cell carcinoma syndrome. Thus, the diagnosis of OKC, particularly recurrent OKCs, should raise the possibility of this syndrome.
This case illustrates the point that the diagnostic features are often not retained in those regions of the cyst that are inflamed. The presence of squamous hyperplasia and the formation of rete pegs may closely resemble a common inflammatory odontogenic cyst. The entire lesion must be carefully evaluated histologically for the distinctive lining features with special attention to the non-inflamed areas.
In some odontogenic cysts, the squamous lining exhibits prominent orthokeratosis with a granular cell layer. These orthokeratinized odontogenic cysts are sometimes still designated as an orthokeratinized variant of OKC even though they lack the high recurrence rate of the parakeratinized OKC. Furthermore, the orthokeratinized odontogenic cyst lacks the characteristic pallisading of the basal cell layer.
