Messages from Kennichi Kakudo, MD, PhD to a person to be an expert of the cytopathology

The 4th edition of WHO Classification Tumors of Endocrine Organs was published in July, 2017. Borderline tumors of follicular cell origin were incotporated in this thyroid tumor classification very first time. I hope the introduction of the borderline tumor category in thyroid tumor classification will open a new era where pathologists have 3 choices for their diagnoses: benign, borderline, or malignant. Pathologists are no longer forced to decide between benign and malignant—it can be a borderline or precursor tumor. I believe this causes significant changes not only in pathology practice, but also brings significant impacts on clinical management of patients. It opens a new era for endocrinologists and endocrine surgeons to have 3 treatment options for patients with thyroid nodules, treat, not treat, or close follow-up (active surveillance), which would be different from the current clinical management with 2 choices (treat or not treat).  

Borderline/Precursor Tumours in the 4th Edition, 2017 WHO Classification of Thyroid Tumours.
2		Hyalinizing Trabecular Tumour
2A		Other encapsulated follicular patterned thyroid tumours
	2A-1	Uncertain malignant potential (UMP)
		2A-1-1:Follicular tumour of Uncertain malignant potential (FT-UMP)
		2A-1-2:Well differentiated tumour of Uncertain malignant potential (WDT-UMP)
	2A-2	Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)