Fine needle aspiration of the thyroid: A cytohistologic correlation and study of discrepant cases

OBJECTIVE: Fine needle aspiration (FNA) is a reliable method in the initial assessment of thyroid nodules. The purpose of this study was to evaluate the causes for discordance between the interpretation on FNA and the pathologic findings in the resected thyroid. METHODS: A computer search of all thyroidectomy specimens with previous FNA from January 1998 to December 2001 was obtained from the files of the Lauren V. Ackerman laboratory of surgical pathology, Barnes-Jewish Hospital. Excluded from the study were those FNAs performed for suspected and confirmed metastatic disease to the thyroid as well as those cases unavailable for review. A total of 45 FNA cases were identified with cytologic and histologic discrepancies. RESULTS: Of the 1253 individual thyroid FNA performed during the study period, 255 patients (20%) subsequently had an open surgical procedure on the thyroid. Of those who underwent surgery, 196 cases (77%) were concordant, whereas 45 patients (18%) were discordant, and 14 cases were excluded due to unavailability of slides for review (for example, returned consult slides). The causes of the 45 discordant cases were: 20 cases (44%) were unsatisfactory for diagnosis, 14 cases (31%) were due to interpretation error (false positive), and 11 cases (24%) were due to sampling error (false negative). CONCLUSIONS: The most common causes of our discrepant cases are those whose FNA diagnosis was interpreted as unsatisfactory for diagnosis, in 20 (7.8%) of 255 surgical cases. The false negative rate due to sampling error in 11 (4%) of 255 cases was mainly due to the presence of microscopic papillary thyroid carcinoma (PTC); the false positive rate was due to interpretation error in 14 (6%) of 255 cases, and those were explained by the occurrence of overlapping cytologic features among adenomatous nodules, follicular neoplasms, the follicular variant of PTC, and Hashimoto\u27s thyroiditis

Fine needle aspiration cytology of a dedifferentiated liposarcoma: Report of a case with histologic and immunohistochemical follow-up

BACKGROUND: Dedifferentiation is a histologic progression of a neoplasm from low grade to high grade histology. It occurs in tumors of the retroperitoneum and in those undergoing treatment. This usually occurs in the setting of radiation or chemotherapy or as a spontaneous process over a long period. The features of dedifferentiation can be toward any mesenchymal element of the underlying neoplastic process. CASE: We report the cytologic features of a dedifferentiated liposarcoma arising in a 76-year-old man who had a history of well-differentiated liposarcoma. Papanicolaou- and Diff-Quik-stained smears from a radiologically guided fine needle aspiration biopsy showed a hypercellular sample. The smears showed a mixed population of cells. There were multinucleated, pleomorphic giant cells with abundant cytoplasm, smaller clusters of cells with a high nuclear/cytoplasmic ratio and cells with spindled and elongated nuclear features. The follow-up surgical resection specimen showed a dedifferentiated liposarcoma with strong and diffuse immunoreactivity to vimentin, desmin and CD68 in the large, pleomorphic cells; focal and weak immunoreactivity to smooth muscle actin and S-100 in these cells; and strong and focal immunoreactivity to desmin, smooth muscle actin and muscle-specific actin in the spindle cells. This supports the dedifferentiated components of this tumor to be of fibrohistiocytic and leiomyosarcomatous differentiation. CONCLUSION: Dedifferentiation of a well-differentiated liposarcoma should be entertained in the setting of a mass lesion in the retroperitoneum in patients with prior histories of well-differentiated liposarcoma. The radiologic features of a particular neoplastic process can be very helpful in determining the nature of this process