Abstract
In the recently published 8th edition of the AJCC Cancer Staging Manual, new pathological elements are required for the N and T category determinations for oral cavity cancers. This includes determination of depth of tumor invasion and assessment of metastatic lymph nodes for extranodal extension. Although definitions and some guidance are provided for the interpretation of these elements, pathologists frequently encounter ambiguous situations that may result in interobserver and intraobserver variability. Pre-existing staging elements, such as assessment of bone invasion, can also be problematic to interpret. Difficulties in the interpretation of depth of invasion, bone invasion and extranodal invasion are discussed, with examples. Communication with the surgeon, proper specimen orientation, gross examination and sampling are crucial to assessment of these elements. Liberal use of deeper levels and submission of additional sections is suggested. Although general staging guidelines encourage clinicians and pathologists to choose the lower category when there is ambiguity, pathologists may choose to discuss difficulties in the interpretation of specific cases at interdisciplinary tumor boards, to allow a more informed choice of treatment on the part of treating physician and patient. More discussion is required among pathologists to develop specific guidelines for the interpretation of these staging elements.