TIR 3. INCONCLUSIVE/INDETERMINATE (Follicular proliferation)
This category encompasses all follicular-patterned lesions: adenomatoid hyperplasia, adenoma, microinvasive follicular carcinoma, oxyphilic cells lesions and some cases of follicular variant of papillary carcinoma. In these cases only histology (and not cytology alone) can provide a diagnostic conclusion. This category accounts approximately for 20% of the cytologic reports.
About 80% of the TIR 3 diagnoses are benign lesions whereas only 20% of them result as malignant tumors after the histologic examination.
Some immunohistochemical markers such as Galectin-3, HBME-1, Cytokeratin 19 may improve the accuracy of the cytologic diagnosis. Although they do not have a well established predictive value, they can be used following strict diagnostic protocols to discriminate the positive cases (surgical option) from the negative ones (follow-up).
Some cases characterized by cytologic alterations too mild to be included in TIR 4 category too marked to be included in the benign category (TIR 2), could be classified as TIR 3. The choice of whether including or not these samples in the “low risk” category must be supported by an adequate description in the medical report.
Operative suggestion. Surgical excision of the lesion and histological examination.
Intraoperative histological examination is not recommended. The surgical option should be evaluated in the clinical and imaging setting.