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Pathology · patient case with 2 questions

Two radiolucencies that are not what their names suggest

Patient: Two patients

Chief Complaint: A: incidental finding at a new patient examination. B: incidental finding on a panoramic taken before orthodontic assessment.

Background: A, 34-year-old male: asymptomatic, no history of trauma or caries in the region. B, 25-year-old female: healthy, no extractions ever performed.

Findings: A: an inverted pear-shaped radiolucency between the roots of the maxillary lateral incisor and canine, with the roots divergent. BOTH teeth respond normally to cold and electric pulp testing. B: a well-defined corticated radiolucency in the posterior mandible occupying the position where a third molar never developed. No tooth is present and none is visible elsewhere.

Question 1

How should Patient A's lesion be interpreted?

  1. It is a normal anatomical variant requiring no investigation
  2. It is a radicular cyst arising from the lateral incisor
  3. It is a fissural cyst arising from epithelium trapped at the fusion of the globular and maxillary processes
  4. It is globulomaxillary in LOCATION, but this is not a distinct entity — the diagnosis must be established by biopsy
Show answer and explanation

Correct answer: D. It is globulomaxillary in LOCATION, but this is not a distinct entity — the diagnosis must be established by biopsy

  • A. An expanding radiolucency between two vital teeth always requires investigation. Nothing about this site makes a lucency normal.
  • B. A radicular cyst requires a NON-VITAL tooth. Both teeth here respond normally to pulp testing, which is precisely why vitality testing is the first investigation — it excludes the commonest cause in a single step.
  • C. This is the classic teaching that has been ABANDONED. The globular and maxillary processes do not fuse in a manner that traps epithelium at this site, and the fissural theory is no longer accepted.
  • D. CORRECT. ‘Globulomaxillary cyst’ describes a LOCATION, not a diagnosis, and it has been removed from current classification. Lesions found in this site prove on histology to be ODONTOGENIC — radicular cyst, lateral periodontal cyst, odontogenic keratocyst, periapical granuloma, odontogenic myxoma or central giant cell granuloma. The inverted-pear shape with divergent roots is a description of appearance, not a diagnosis. The sequence is therefore: pulp test both teeth, then biopsy.

Note: The ‘median mandibular cyst’ has met the same fate and for the same reason. The NASOPALATINE DUCT CYST, by contrast, remains an accepted developmental non-odontogenic cyst — it arises from remnants of the nasopalatine duct, appears as a round or heart-shaped midline lucency at or just behind the incisive foramen, and is diagnosed when it exceeds about 6 mm or produces symptoms or expansion.

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Question 2

What is Patient B's lesion, and why does the diagnosis matter?

  1. Traumatic bone cyst — an empty cavity requiring only surgical exploration
  2. Primordial cyst — and in current classification the great majority prove to be odontogenic keratocysts
  3. Dentigerous cyst — enucleate with the associated tooth
  4. Residual cyst — left behind after a previous extraction
Show answer and explanation

Correct answer: B. Primordial cyst — and in current classification the great majority prove to be odontogenic keratocysts

  • A. A traumatic (simple) bone cyst is an empty, unlined cavity that characteristically SCALLOPS UP between the roots of adjacent VITAL teeth. It is unrelated to a missing tooth germ, and it occurs typically in young patients in the posterior mandible.
  • B. CORRECT. A PRIMORDIAL CYST develops from the enamel organ BEFORE any hard tissue forms, so it occupies the position of a tooth that NEVER DEVELOPED — most often the third molar region, exactly as here. The reason the diagnosis matters is that the great majority of lesions historically labelled primordial cysts prove on histology to be ODONTOGENIC KERATOCYSTS, and the term has largely been superseded for that reason. That changes management entirely: OKCs recur at a high rate and require thorough enucleation with adjunctive treatment such as peripheral ostectomy or Carnoy's solution, plus long-term radiographic follow-up.
  • C. A dentigerous cyst forms around the CROWN of an unerupted tooth and requires a tooth to be present. There is no tooth here.
  • D. A residual cyst is a radicular cyst left behind after extraction of the causative NON-VITAL tooth. This patient has never had an extraction, and a tooth must have existed for this diagnosis to apply.

Note: Multiple keratocysts, or a keratocyst in a patient under about twenty, should prompt screening for GORLIN-GOLTZ syndrome — skull film for falx calcification, chest film for bifid ribs, dermatology referral for basal cell carcinomas.

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