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The Case of a Subtle Expansion of the Mandible

Case Challenge Number: 12

Diagnostic Information

Medical History This apparently healthy patient had seasonal allergies that were managed by pseudoephedrine when symptoms would arise. The patient suffered a fracture of the left fibula as the result of a motor vehicle accident in 1988. No other organ system abnormalities were noted. Significant social history included a 5‑year history of cigarette smoking, and he admitted to the continued use of tobacco products. Clinical Examination Findings The oral and maxillofacial surgeon palpated a slightly expansile area of the right mandible in the medio-lateral dimension. All mandibular surfaces were bony hard and without evidence of crepitus. The inferior border of the mandible was also intact and without obvious expansion. There were bilateral, < 1 cm, movable and non-tender lymph nodes in the submandibular region. Sensory neural examination revealed intact tactile function of all areas served by the inferior alveolar nerve.  Cranial nerves II – XII were evaluated and assessed as being within the range of normal. All teeth tested vital to electrical stimulation. Occlusion was normal, without evidence of tooth movement. (Figure 1)  All mucosal surfaces were intact, although some expansion of the right buccal plate was noted. (Figure 2) Minimal facial asymmetry was appreciated, when evaluating the frontal view of the face (Figure 3), but the changes were not obvious in the profile view. (Figure 4)

Figure 1. Occlusion and view of buccal vestibule.

Figure 2. Right side vestibule showing some expansion.

Figure 3. Preoperative photograph of full face with slight asymmetry noted.

Figure 4. Preoperative photograph showing the facial profile with no asymmetry noted from this view.

Preliminary Radiographic Findings A cropped pantomographic radiograph revealed a well-defined, 5.0 x 2.0 cm radiolucent lesion. (Figure 5)  Focal areas of the radiographic border of the lesion were somewhat scalloped, including areas between the roots of the teeth. (Figure 6)  The inferior cortex was focally thinned, but was not displaced. In addition, the inferior alveolar canal remained discernible without evidence of disruption or displacement.  Several circular areas displayed increased radiolucent changes consistent with a multilocular pattern and a more aggressive process. These lytic changes were most obvious in the pericoronal area of the third molar and extended to the distal of the second premolar. Although the lesion was well demarcated, the margins varied from being corticated to non-corticated.

Figure 5. Pantomographic radiograph; evidence of multilocularity is seen.

Figure 6. Pantomographic radiograph showing scalloping between the roots and along the inferior border of the mandible.

Incisional Biopsy and Microscopic Findings

Due to the significant size of the lesion, an initial incisional biopsy was performed under local anesthesia and conscious sedation in order to establish a definitive diagnosis. Unfortunately, the initial biopsy was inconclusive and the patient was referred to Eisenhower Army Medical Center, Ft. Gordon, GA, for an additional biopsy and treatment. During that procedure, abundant gelatinous material was obtained and the specimen was submitted in formalin for routine histopathologic examination. The gross specimen consisted of three fragments of soft tissue, which ranged from 1.5 x 1.5 x 0.4 cm to 0.6 x 0.4 x 0.3 cm.

The low power photomicrograph displayed variably dense fibrocollagenous connective tissue along the edge. The lesion itself dominated the image and was characterized by loose myxoid fibrocollagenous connective tissue that was hypocellular. (Figure 7)  The medium power photomicrograph displayed loose and myxoid fibrous connective tissue with some small vascular channels interspersed as well as some extravasated erythrocytes. The nuclei were spindle-shaped to stellate and evenly dispersed throughout the specimen.  Although the nuclei were somewhat hyperchromatic, they were uniform in appearance and without evidence of mitotic activity. (Figure 8)  The high power photomicrograph showed similar findings. (Figure 9)

Figure 7. Low power photomicrograph showing a lesion that is dominated by loose, myxoid, and fibrocollagenous tissue that is hypocellular (Hematoxylin and eosin, original magnification 40x).

Figure 8. Medium power photomicrograph displaying generally loose and myxoid fibrous connective tissue with some small vascular channels. (Hematoxylin and eosin, original magnification 100x).

Figure 9. High power photomicrograph showing uniform nuclei within the myxoid stroma. These nuclei are spindle-shaped to stellate and evenly distributed across the field. (Hematoxylin and eosin, original magnification 400x).

Advanced Imaging Computer-assisted tomographic images (CTs) were ordered, and both axial and coronal cuts were reviewed. The axial CT displayed the multilocular nature of the lesion and explained the circular lytic areas that were seen on the pantomograph. (Figure 10)  In addition, the axial CT demonstrated the mandibular expansion in addition to the thinning and scalloping of the cortices. (Figure 11)  Similarly, the coronal CT displayed the mandibular expansion of the lesion from another view. (Figure 12)

Figure 10. This axial CT displays the multilocular nature of the lesion and explains some of the circular lytic areas seen on the pantomograph.

Figure 11. This axial CT displays the mandibular expansion, thinning of cortices, and scalloping of the cortices

Figure 12. This coronal CT displays the mandibular expansion from another view.