PTC is a cytologic diagnosis. If you are a good cytopathologist you are virtually always right if you call it PTC outright. There are some "suspicious" cases which usually don't proceed to total thyroidectomy off of the FNA, unless there are other reasons to do so.
Indeed. Obvious cases are obvious (papillary architecture, nuclear inclusions, nuclear crowding with grooves, etc.). As for the challenging cases, there have been a few studies that even extend these impox PTC studies to cytology cases; although due to low case numbers, the question still remains as to the universal applicability of these immunomarkers.
Thyroids can be frustrating in that histology is deemed the gold standard. The malignancy risk stratification scheme, especially laid out in the Bethesda System book, is based on numerous studies from a variety of institutions. Unfortunately, the gold standard is not perfect as there is disagreement even amongst surgical pathologists especially when it comes down to what can be called a follicular variant of PTC versus an adenomatoid nodule, for example. Some pathologists are very conservative in calling follicular-patterned nodules FV-PTCs whereas others seem to call every dominant nodule a FV-PTC. As FV-PTCs usually don't kill people anyway, I imply from this that calling something an FV-PTC or a benign nodule are low-risk diagnoses anyway. Cynically speaking, in this culture of medical malpractice and pathologists covering your own arse, there are isolated cases where a FV-PTC metastasis is discovered years after the surgery only to discover that the initial thyroidectomy specimen had been diagnosed previously as benign. Maybe this is why some overcall FV-PTCs?
Again, if there is so much variation in how follicular-patterned lesions are called FV-PTC, is this really a good gold standard? There is increased appreciation of using molecular studies to stratify thyroid nodules. If detecting RET-PTC rearrangements, B-Raf mutations, etc are considered to be synonymous with malignancy, so be it...maybe molecular studies should be the gold standard and should be done for every thyroid nodule. Problem is, these studies would not be expected to pick up mutations and rearrangements in every cancer case (of course, that depends on the definition of "cancer" by whatever "gold standard"). So it begs the question of what is the negative predictive value.
Hence, if the gold standard is frought with interobserver variability and imprecision, how does this affect thyroid cytology? Already, there is quite a range in malignancy risk percentages associated with a given category of cytologic thyroid FNA interpretations (e.g., atypical, follicular neoplasm, and Hurthle cell neoplasm). Anything short of "suspicious for PTC" or "PTC" diagnoses...the risk stratification lines are blurry. I suspect that this could represent increased "noise" in the system due to the variability in the gold standard.
Simply put, I wonder if the blind are leading the blind.
