Automatic upstaging of tongue squamous cell carcinoma with lateral extrinsic muscle involvement is not justified

Validation of the eighth edition AJCC staging system in early T1 to T2 oral squamous cell carcinoma

“…The major changes in AJCC eighth edition included the incorporation of DOI into the staging system and exclusion of extrinsic muscle involvement from T4 staging of tongue cancers. This exclusion is justifiable due to the close proximity of certain extrinsic muscle groups to the mucosal surface, which would erroneously upstage thin tumours to T4 with no prognostic implications …”

“…This exclusion is justifiable due to the close proximity of certain extrinsic muscle groups to the mucosal surface, which would erroneously upstage thin tumours to T4 with no prognostic implications. 15,16 The incorporation of DOI into the new AJCC staging was based on the recommendations of the ICOR 7 who proposed a modified primary tumour staging for oral cavity carcinomas by using data from 11 centers. This staging was subsequently validated using data from Memorial Sloan-Kettering and the Princess Margaret Hospital before the publication of the new staging manual.…”

Predicting the Prognosis of Oral Tongue Carcinoma Using a Simple Quantitative Measurement Based on Preoperative MR Imaging: Tumor Thickness versus Tumor Volume

“…The "deep" descriptor overlooked the fact that considerable portions of extrinsic muscles lie in a very superficial plane. 13 With growing evidence that tumor thickness or tumor volume might be a more accurate outcome predictor, our present study concentrated on and compared the predictive value of tumor thickness and tumor volume measurement based on preoperative MR imaging for short-term prognosis of oral tongue carcinoma, especially for lymph node metastases and local recurrence.…”

Clinical Outcomes in pT4 Tongue Carcinoma are Worse Than in pT3 Disease: How Extrinsic Muscle Invasion Should be Considered?

“…[7][8][9] Relevant to this discussion of EMI are past studies recommending that EMI be excluded from the T4 classification. 10,11 In an anatomic study, Boland et al found that the extrinsic tongue muscles exist a few millimeters below the mucosa, especially laterally, such that involvement does not necessarily reflect deep invasion or aggressiveness. 10 This may explain the four patients in the present study for whom DOI was \10 mm, although EMI was present on histopathology.…”

“…Further analysis revealed that although EMI significantly affected OS and DFS, it did not impact disease-related survival. 11 These authors concluded that EMI should not be a criterion for the T4 category. In contrast, Liao et al identified EMI pathologically, which is arguably a more definitive assessment of EMI.…”