A Connective Tissue Neoplasm of the Mandibular Angle Mimicking Stafne’s Bone Cavity on Panoramic View

Discussion

This case report shows a mandibular lesion which, when viewed from a PV, meets the diagnostic criteria of SBC. Thus, diagnosis based on PV would have justified the assessment that the lesion is a bone change not requiring treatment. Only the supplementary three-dimensional radiography revealed an intraosseous lesion indicating the need for surgical intervention. Reliance on a sufficiently precise SBC diagnosis using plain radiography like PV is no longer justified. Alternatively, three-dimensional sectional imaging is the preferred imaging modality to establish a lesion’s adequate topographical representation (7).

SBC. The eponymous name SBC gives credit to the author who described the mandibular anomaly on plain radiographs (1-4). The cup-like depression on the lingual side of the mandible has since been described in several radiological studies (4, 5). The localization in the angle of the jaw is the most common manifestation of SBC and the initial description of the lesion has focused entirely on this region (3). However, systematic analyzes of published studies, case series, and individual reports have shown that such bone depressions can occur in many mandibular sites (8-15). The etiology of the lesion is unknown. The retention of the eponymous definition of the entity in medical terminology may also be due to the lack of a coherent pathogenetic concept that explains the numerous variants of the phenomenon. Some authors prefer the theory of local bone erosion due to pressure from the neighboring salivary glands as the cause of SBC (16). However, some authors have pointed out that no salivary gland tissue can be detected in the lesions (7). Rather, the lesion is filled with adipose tissue, blood vessels, etc. (6, 7, 14). The soft tissue of the osseous lesion in this examination confirms the exclusion of salivary gland tissue. Blood vessels and connective tissue were essential components of the lesion mixed up by foci of ossification.

In order to assess the significance of the case presented here, it is crucial to consider that the vast majority of studies on SBC are based on plain radiographs (17). In fact, it is characteristic of SBC that, since it’s definition (3), diagnosis has primarily been based on radiological findings depicting the region of interest in two dimensions (1). Until a few years ago, the number of systematic studies on SBC was relatively small (11). Interest in the radiological diagnosis of SBC has increased in recent years, probably due to improved skeletal diagnosis of the facial skull using CBCT (10). Atypical SBCs were identified using CBCT, for example bi- or trilobated types, but also SBC-like lesions of the mandible in almost all locations of the mandible (11, 13). Bicortical lesions (15), lesions where the lower edge of the jaw is dissolved (14), as well as multilocular manifestations, are counted among the variants of SBC (12). The lesion can also be detected in patients with tumor predisposition syndrome (18).

The shape of the lesion can differ significantly from the common oval lesion running below the canal (13). Unilateral and lingual depression is by far the most common variant (3), but vestibular depressions in the cortical bone are also counted among the variants of SBC by some authors (4, 6). On the other hand, the cortical impression on one side can be associated with expansion on the other side and thus, dictate the skeletal finding of suspected pressure atrophy and opposite hypertrophy of the bone (19). However, a constitutive feature of SBC is the impression of the bone from the outside. Strictly intra-osseous lesions are not included in the category ‘SBC’. The case presented here can therefore be ruled out as a case of SBC by the definition referring to X-ray imaging, but only after plain radiography has been supplemented by cross sectional imaging.

Complementary to the identification of a very variable SBC phenotype, the demands are increasing on the reliability of its initial radiological diagnosis (20, 21). The present case shows that SBC cannot be reliably diagnosed using PV. In the individual case of radiological diagnostics of jaw lesions as well as in the systematic examination for SBC in radiological studies, the findings should refer to cross sectional images. Adequate diagnosis of radiotranslucency is crucial because neoplasms can take the shape of SBC and even develop at typical mandibular locations (20, 21). The presented case exemplifies the importance of this requirement for the current diagnosis of jaw lesions. Information on the prevalence of SBC with reference to the analysis of PV is worth exploring according to the presented case (5, 17).