Diagnostic power and pitfalls of intraoperative consultation (frozen section) in rhabdomyosarcoma

Intraoperative consultation plays an important role in the management of soft tissue sarcomas, such as rhabdomyosarcoma. In this study, we aimed to draw attention to the important points during frozen section interpretation, and analyse the accuracy of frozen diagnosis in rhabdomyosarcoma patients.

The cases, both diagnosed as rhabdomyosarcoma or followed with a history of rhabdomyosarcoma, and interpreted with intraoperative consultation (frozen section) between 2000 and 2013 were culled from pathology archives. The diagnoses were confirmed by desmin and myogenin, immunohistochemically. The frozen and final diagnoses were noted of 21 biopsy specimens of 19 patients. Sensitivity and specificity of intraoperative consultation were calculated regarding to the major diagnostic discrepancies leading to a change in surgical management of the patient, after exclusion of the cases deferred to paraffin section.

Of the evaluated 21 biopsy material, 3 (14%) were misdiagnosed: Of the 2 false negative embryonal rhabdomyosarcoma cases, sample was not representative of the tumor, and there was chemo/radiotherapy induced changes in the other case. In the only false positively diagnosed case with a known history of rhabdomyosarcoma, inflammatory cells were misinterpreted as small round cell neoplasm. In 5 (29%) of 21 biopsies, a frozen diagnosis could not be given, and the diagnosis was deferred. Six cases (29%) were evaluated with cytological squash or imprint preparation; none of the misdiagnosed cases was evaluated with adjunct cytological preparation. Six of 8 misdiagnosed or deferred biopsies showed morphological changes secondary to radiotherapy and/or chemotherapy. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated as 85%, 67%, 92% and 50%, respectively.

Intraoperative consultation for rhabdomyosarcoma is a reliable tool with high sensitivity and fair specificity. Cases with treatment effect may lead to diagnostic difficulties, especially false negative results. Understanding the diagnostic algorithm of surgeon may prevent misdiagnosis of frozen specimen. Our results also emphasize the diagnostic role of intraoperative cytology as an adjunct to frozen section.