In Reply

We thank the authors for their comments on the revised College of American Pathologists thyroid cancer protocol.1 The authors raise a valid point regarding the classification of isolated psammoma bodies in lymph nodes without viable tumor cells. This issue had generated considerable debate among the committee members as well. As the authors mention, the focal point of this argument is the generic N classification rule set provided in the 7th edition of the AJCC Cancer Staging Manual of the American Joint Committee on Cancer, specifically, that “lymph nodes with ITC (isolated tumor cells) only (are) generally staged as pN0,” unless “disease specific rules” apply, as in melanoma.2 While our committee generally acknowledges that psammoma bodies in lymph nodes are a very close conceptual approximation of ITCs, we ultimately felt these cases represented a unique scenario that was not specifically addressed by these N classification rules.Indirectly, there is emerging evidence to support the authors' stance, since even patients with small-volume viable tumor metastases have a low locoregional recurrence rate3 and postoperative detectable serum thyroglobulin concentrations4 similar to those of N0 patients. (As a technicality, the study by Lang et al4 quoted by the authors to reflect the prognosis of ITCs actually stratifies nodal disease on the basis of a 2-mm cutoff, which encompasses N1 “micrometastases,” ITCs, and possibly isolated psammoma bodies. This study does not specifically enumerate the number of cases that truly showed clusters of cells less than 0.2 mm, thus fulfilling the definition of ITCs.) While it is reasonable to assume that isolated psammoma bodies in lymph nodes will fit into this indolent category, sufficient direct evidence (ie, a focused assessment of this parameter) is lacking.Admittedly, this is a rare scenario in patients who have undergone a formal central and/or lateral compartmental neck dissection. We agree with the authors that finding psammoma bodies in neck lymph nodes should prompt a more thorough investigation for viable tumor, including additional levels, but we do not agree that NX will necessarily pose a danger of “overemphasis,” particularly because clinicians are becoming increasingly aware of the indolent outcome in patients with small-volume nodal disease regardless of whether it is designated as N0(ITC), N1a, or NX.5 An advantage of an NX designation as it stands now is that in situations where isolated psammoma bodies are noted incidentally or in a limited lymph node dissection or excision, it may prompt a more thorough examination of the neck to ensure low-volume disease.In summary, we understand the authors' stance regarding isolated psammoma bodies in lymph nodes and will revisit this as needed. Since the upcoming 8th edition of the AJCC cancer staging system is currently under way, this will be an opportune time for clarification of this issue.

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