Definition and Clinical Significance of Vascular Invasion in Thyroid Carcinomas Derived from Follicular Epithelium
O Mete, SL Asa. University Health Network, Toronto, Canada; Istanbul Faculty of Medicine, Istanbul, Turkey
Background: The diagnosis of well differentiated thyroid carcinoma (WDTC) is based on the presence of nuclear features of papillary thyroid carcinoma or capsular and/or vascular invasion by a follicular neoplasm. The criteria for vascular invasion are controversial. Several reports have suggested that angioinvasion is not a predictor of bad prognosis, but these results may be attributed to application of inappropriate criteria. We reviewed retrospectively the clinicopathological features of a series of angioinvasive thyroid carcinomas derived from follicular epithelium as defined by the most rigid criteria in order to determine whether rigid criteria for vascular invasion have clinical significance.
Design: A series of 4000 thyroid carcinomas derived from follicular epithelium were obtained from the files of University Health Network between September 2001 and August 2009. Using the criteria of tumor cells invading through a vessel wall associated with thrombus adherent to intravascular tumor, 116 angioinvasive carcinomas were identified; anaplastic thyroid carcinomas were excluded. Patient age and gender, tumor size, histological tumor type and variant, the presence of multifocal disease, extra-thyroidal extension (ETE), lymph node and surgical margin status were collected. The clinical charts of the patients were reviewed to determine the presence of distant metastasis and/or local tumor recurrence during follow-up.
Results: Tumors from 116 patients (35 males, 81 females, age 22-84, mean 52.39 years) ranged from 0.8 cm to 11.5 cm (mean 5.08 cm) and included 82 WDTCs (71%) 22 poorly differentiated thyroid carcinomas (PDTCs) (19%) and 12 WDTCs with focal dedifferentiation (10%). Multifocal disease and ETE were present in 38 (33%) and 25 (22%), respectively. Surgical margins were involved in 56 (50%). Lymph node metastases were found in 42 of 70 patients (60%) that had undergone lymph node dissection. Follow-up information was available for 73 cases; follow-up time ranged from 1 month to 8 years. 24 patients developed distant metastasis (33%) and 27 patients had local tumor recurrence (37%). The most common metastatic sites were lungs (23 patients), bone (11 patients), brain (2 patients) and liver (1 patient). Distant metastasis originated from 14 WDTCs (58%), 6 PDTCs (25%) and 4 WDTCs with focal dedifferentiation (17%).
Conclusions: Using rigid criteria, the identification of vascular invasion predicts distant metastasis in patients with thyroid carcinomas, especially in WDTCs.
Monday, March 22, 2010 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 81, Monday Morning