Lymph Node Metastases in Thyroid Carcinomas: CT Diagnosis

PURPOSE: To determine the usefulness of CT for diagnosing metastases to primary and secondary echelon lymph nodes (LNs) and to investigate various CT findings of metastatic LNs in thyroid carcinomas. MATERIALS AND METHODS: We retrospectively reviewed the CT and histologic findings in 59 patients with thyroid carcinomas who had undergone thyroidectomy and neck dissection. Primary echelon LNs (Level VI) were removed by central neck dissection in all patients, and in 21, a total of 136 levels of secondary echelon LNs (Level II-V) were excised away by lateral neck dissection. CT criteria of metastatic LNs included large size, significant homogeneous enhancement, calcification, and cystic change. We evaluated the ability of CT to detect primary and secondary echelon LN metastasis and tried to determine which CT features were useful for the diagnosis of LN metastasis. RESULTS: Histologically, LN metastasis was found in 31 (53%) of 59 patients, including 30 with metastasis to primary echelon LNs. Of the 136 levels of secondary echelon LNs resected in 21 patients, 44 were found at histology to harbor metastatic foci. The sensitivities, specificities, positive and negative predictive values, and accuracies of CT in the diagnosis of metastasis to primary and secondary echelon LNs, respectively, were 27% and 93%, 100% and 93%, 100% and 87%, 57% and 97%, and 63% and 93%. While all secondary echelon LNs with at least one of the following CT criteria-large size (n=19), cystic or necrotic change (n=14), or calcifications (n=8)-were histologically proven to be metastatic, six (24%) of 25 such LNs with a sole sign of significant enhancement at CT were found to be due to reactive lymphadenopathy. CONCLUSION: Although CT was unable to detect metastasis to primary echelon LNs, it was useful in the detection of secondary echelon LN involvement. Large size, cystic change, and calcification are considered highly reliable signs of metastatic LNs.

Tuberculous Abscess of the Thyroid Gland: A Case Report of CT Demonstration

We report a case of tuberculous abscess of thyroid gland in 32-years old female. On CT scan, multiple peripheral enhancing low density abscess were found in the right thyroid gland. Abscess cavity with skin and subcutaneous manifestations were also noted in the right anterior neck. This was confirmed as chronicgranulomatous caseous necrosis and acid-fast bacilli were identified by Ziehl-Neelsen stain.

CT Findings in the Differential Diagnosis of Benign and Malignant Thyroid Tumor

PURPOSE: We analysed CT findings of thyroid mass to determine the difference between a benign and a malignant mass and to evaluate the differential findings, if any. MATERIALS AND METHODS: The subjects were 87 cases with apathologically proven thyroid mass (malignancy in 66 cases, benign mass in 21 cases). CT findings were retrospectively analysed. For the primary masses, bilaterality, size, margin, attenuation of the mass, spotty portion with distinct high attenuation(which may suggest calcification), necrosis, cystic change, solid portion within the cyst, and invasion of adjacent structures were evaluated. For the lymph nodes, size, high attenuated spotty portion, necrosis, cystic change, and solid portion within the cyst were evaluated. CT findings of thyroid masses and lymph nodes were evaluated in order to determine whether these were benign or malignant. Statistical analysis was performed using the Mann-Whitney U-Wilcoxon rank sum test. RESULTS: In malignant masses, compared with benign, an indistinct margin of the mass(48% vs 19%), invasion of adjacent structures(53% vs 0%), and associated lymph node enlargement(50% vs 0%) were more frequent. With regard to bilaterality, size, attenuation, high-attenuated spotty portion(which may suggest calcification), necrosis, cystic change, and solid portion within the cyst, there was no significant difference between benign andmalignant masses. In masses of the former type, enlarged lymph node or invasion of adjacent structure were not seen at all. When the papillary solid portionwithin the cystic mass was additionally evaluated, papillany carcinoma was the most common finding(77% 14\18). CONCLUSION: General findings of malignancy such as margin, invasion of the mass, and lymph node enlargement are of help in the differential diagnosis of a malignant mass. High attenuated spotty portion, which may suggest calcification within the mass, or size of the mass are non-specific findings, and are not helpful in differential diagnosis. The papillary solid portion within the cyst of the mass could suggest papillary carcinoma as a first possibility and could be helpful in differential diagnosis.