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Tumors of parafollicular cells and nonepithelial tumors occur less frequently than tumors derived from follicular cells. This review summarizes the histologic and cytologic features of these neoplasms and the nonneoplastic diseases that often have to be included in the differential diagnosis of thyroid tumors. Also, the role of fine-needle aspiration biopsy and frozen section interpretation in the diagnosis of thyroid nodules are discussed.

Every year, 18,000 new thyroid cancer cases are reported in the United States, representing 1.2% of the total number of new cancer cases of all sites. Thyroid cancer accounts for 1,200 deaths, or 0.2% of the total number of deaths related to cancer. 1 Over the last two decades, there has been important progress in our understanding of tumors of the thyroid gland, from both histopathologic and etiopathogenetic points of view. In the first part of this review, we summarize the histologic and cytologic features of benign and malignant tumors of the thyroid gland that derive from follicular cells.

Background: Ductal carcinoma in situ (DCIS) is detected more often since the advent of mammography. A standardized pathologic staging and grading system does not exist, but nuclear grade is assuming greater importance. The history of DCIS is long, and its treatment is a controversial issue in breast cancer today. Methods: Data have been reviewed regarding the role of HER-2 expression as a prognostic variable, as a predictive factor for response to chemotherapy and hormonal therapies, and as a directed therapeutic target for breast cancer. Results: The NSABP protocol B06 revealed a recurrence rate of 43% in patients treated with local excision alone. Half of recurrences are still DCIS, but 50% are invasive. Local control is markedly improved by the addition of radiation. Recurrence is also minimized by careful cytologic review of margins. Sentinel lymph node biopsy has resulted in more accurate nodal staging. Conclusions: As a heterogeneous lesion, DCIS may not lend itself to a uniform treatment approach. Careful analysis of resection margins is required. As our understanding of the diagnosis and treatment of this disease develops, a coordinated team approach is optimal.

Our experience with 12 papillary breast lesions included eight intraductal papillomas, three primary papillary carcinomas, and one metastatic papillary ovarian carcinoma. Five of the eight intraductal papillomas displayed diagnostic findings including tridimensional papillary fragments of ductal cells with distended cytoplasmic vacoules and dense scalloped cytoplasm. Three intraductal papillomas displayed cohesive fragments containing epithelial cells surrounding metachromatic, globoid, and cylindrical structures that were bright red following Diff-Quik staining and pale blue following Papanicolaou staining. Such unusual findings may raise the differential diagnoses of adenoid cystic carcinoma and collagenous spherulosis. However, the metachromatic material of intraductal papilloma represents type-I collagen-rich stroma of hyalinized fibrovascular stalks, while the material of adenoid cystic carcinoma and collagenous spherulosis represents type-IV collagen. Two of the three primary papillary carcinomas displayed cytologic findings similar to those of intraductal papillomas except for increased anisonucleosis and cell dyshesion, while the third displayed innumerable psammoma bodies similar to the metastatic ovarian carcinoma.