Glandular patterns in a thyroid carcinoma with insular and anaplastic features: a case with possible implications for the classification of thyroid carcinomas

We describe the case of a 33-year-old woman with a thyroid carcinoma showing poorly differentiated (insular), anaplastic, and glandular features, the latter with extensive clear cell changes. Grossly, the well-circumscribed tumor nodule measured 3.6 cm in maximum dimension and was confined to the thyroid. Microscopically, the majority of the tumor was composed of well-defined "insular" nests showing microfollicular formation, high mitotic activity, and areas of necrosis. Other regions, as well as the intervening stroma of the insular nests, were characterized by highly atypical and pleomorphic stromal cells, extensive necrosis, and malignant cartilaginous nodules. Approximately 30% of the tumor was composed of diffuse glandular formations, each of which were lined by elongated, simple columnar cells with basally situated, mildly pleomorphic nuclei, clear supranuclear, periodic acid-Schiff + (and diastase sensitive) cytoplasm, empty lumens, and no myoepithelia or basement membranes. Immunohistochemically, the glandular elements displayed diffuse and strong positivity for thyroid transcription factor-1, bcl-2, and CAM 5.2, sparse positivity for thyroglobulin and Ki67, and diffuse but weak positivity for p53. Calcitonin was negative throughout the tumor. Karyotypic analysis of a primary culture showed a complex hypertriploid karyotype including structural abnormalities of chromosomes X, 1, 4, 6, 9, 13, and 14 in the majority of cells examined. This composite of histologic findings, especially the glandular patterns, is unusual and their prognostic significance is unclear. The patient is alive with no evidence of tumor recurrence or metastasis at 5 months follow-up. Overall, the morphologic and immunohistochemical properties of the glandular component suggests that they are less differentiated than well-differentiated carcinomas and are probably more differentiated than the insular component. This case supports the theory that the various primary carcinomas of the thyroid may represent points along a spectrum rather than distinct entities.