Positive Cytology Findings and a Negative Histological Diagnosis of Papillary Thyroid Carcinoma in the Thyroid: Is It a False-Positive Cytology or a Disappearing Tumor

Abstract

Background: It infrequently occurs that cytologic diagnosis of papillary thyroid carcinoma (PTC) cannot be confirmed by histology after surgery. This phenomenon may be a false-positive cytology or a true disappearing tumor. Objectives: We evaluated patients who had consistent findings of PTC at fine needle aspiration cytology (FNAC) and no evidence of PTC in surgical specimens. Methods: Positive cytology findings and a negative histological diagnosis of PTC in the thyroid was defined as thyroid nodules with FNAC findings of PTC prior to surgery and no evidence of malignancy on histological examination of surgically removed thyroids. We retrospectively reviewed patients who underwent fine needle aspiration (FNA) and thyroidectomy in Asan Medical Center from 2004 to 2012. Results: Six patients were found who fit the definition of positive cytology findings and a negative histological diagnosis of PTC in the thyroid. The FNAC diagnosis of 6 patients was ‘malignancy' suggesting PTC according to the Bethesda system. All patients underwent thyroidectomy with central neck dissection. Three patients had reactive changes after FNA due to needle passage. Among these 3 patients, 2 had pathologically confirmed metastatic PTC in dissected lymph nodes. These 2 patients could be defined as true disappearing PTC in the thyroid after FNA. The remaining 3 patients had neither histologic alterations nor evidence of PTC in the thyroid and lymph nodes specimens. Conclusions: Both disappearing PTC and a false-positive result of FNAC should be considered in patients with positive cytology findings and a negative histological diagnosis of PTC in the thyroid.

False‐positive cytopathology results for papillary thyroid carcinoma: A trap for thyroid surgeons

“…The pathological diagnosis and classification of PTC are usually based on the microscopic appearance of biopsy specimens . Fine‐needle aspiration cytology (FNAC) is widely accepted as a rapid, cost‐effective, and safe method for the diagnosis of thyroid nodules . The positive predictive value of FNAC for malignancy according to the Bethesda system is 97%‐99%, and the sensitivity and specificity of thyroid FNAC have been reported as 65%‐99% and 72%‐100%, respectively …”

“…In this situation, a nodule is underestimated and may be later diagnosed as a malignancy. The rate of false‐positive FNAC for thyroid nodules has been reported as 2%‐10% . The mean risk of malignancy for lesions classified as suspicious for malignancy (class V) and malignant (class VI) is 75.2% and 98.6%, respectively .…”

Vanishing tumors of thyroid: histological variations after fine needle aspiration

“…Another study at Asan Medical Center reported six cases of disappearing PTC. All of these cases had malignant FNA diagnosis, however, none of the specimens showed malignant cells on resection (18). Another interesting finding reported by this group showed that two of the six cases had lymph nodes positive for PTC with no malignancy in thyroid gland.…”

“…In the literature, vanishing tumors of the prostate have been reported for the past few years, the incidence of which is on a decline (15,16). The vanishing tumor phenomenon has been recently described in thyroid gland by some authors (17,18).…”

The diagnosis of cancer in thyroid fine needle aspiration biopsy. Surgery, repeat biopsy or specimen consultation?

“…Jang et al analyzed cases which appeared malignant in cytology examination and proved benign on HP verification [29]. In the literature there are many descriptions of changes that may emerge in the thyroid gland as a result of multiple punctures, such as hemorrhage, vascular thrombosis, fibrosis, infarction, fibrinoid necrosis, cystic degeneration, vascular and capsular pseudoinvasion, angioinvasion and cellular atypia [30,31,32].…”