A 2006 report in Seminars in Pediatric Surgery suggests that such masquerading is not uncommon, in part because dermoid cysts, which account for about 25 percent of all midline cervical abnormalities, often occur in the same midline neck region as TGDCs (Semin Pediatr Surg. 2006;15:70-75). Thus, location alone, assessed pre-operatively by surgeons, is a poor diagnostic indicator; hence, the use of pre-operative ultrasound.
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July 2013Unfortunately, if ultrasound characteristics such as the ones identified by Dr. Propst are not factored in, the imaging modality has proven flawed at best. In a retrospective study coauthored by Nina L. Shapiro, MD, the director of pediatric otolaryngology at the University of California, Los Angeles School of Medicine, pre-operative ultrasound tests in 40 patients with midline neck masses were compared with pathologic results of tissue from the removed mass. The study showed a poor correlation between the results of conventionally interpreted pre-operative ultrasonography (e.g., anechoic, homogenous cysts and pseudosolid, heterogenous masses) and pathology findings (Otolaryngol Head Neck Surg. 2011;144:431-434). The investigators concluded that “the diagnostic accuracy of this imaging modality [ultrasound] may have significant limitations.”
Asked to review the study conducted by Dr. Propst and colleagues, Dr. Shapiro commented that the Toronto researchers “clearly had similar concerns to ours, in that ultrasound findings associated with TGDCs have been notably inconsistent.” That inconsistency is due in part, she noted, to variations in how ultrasound is used to diagnose these masses from one institution to another. Thus, “establishing more widespread [pre-operative ultrasound] criteria may improve the accuracy of this imaging modality.” Such an advance, she agreed, would also help improve the pre-operative counseling of families whose children present with midline neck masses.
But Dr. Shapiro added one caveat. “One must not forget that clinical history, physical examination and intra-operative findings may, in the end, be superior to radiologic studies in these scenarios,” she said. “In our experience, no child underwent unnecessary Sistrunk procedure in the setting of an inflamed lymph node or dermoid/epidermoid cyst. The superficial nature of these lesions, location and gross intra-operative characteristics should point the surgeon in the right direction.”
Other Approaches, Another Fix
Not all pre-operative physical findings can be relied upon to nail down a diagnosis of TGDC or dermoid cyst. One common method that could be problematic is giving patients a swallowing test, according to the 2006 Seminars in Pediatric Surgery review article. If the midline mass in question moves when the patient swallows, then it is often thought to be a TGDC because only that particular mass involves the hyoid bone and the base of the tongue, which elevates during swallowing. But there’s a drawback to the test, the authors noted: It can be very difficult to get younger children to swallow while a physician tries to palpate the mass in question.