Mixed medullary and follicular carcinoma of the thyroid: Report of two cases with an immunohistochemical study

Abstract

Two cases of mixed medullary and follicular carcinoma of the thyroid (MFC) and two cases of thyroid carcinoma resembling MFC are reported with a description of their histological and immunohistochemical features. Two cases of MFC with lymph node metastasis were histologically distinguishable from each other because one had a follicular structure filled with a thyroglobulin (TG)‐positive colloid‐like substance and the other did not have it. Although one of the thyroid carcinomas resembling MFC was similar to the case of MFC with a follicular structure in its primary lesion, it showed no lymph node metastasis. The metastatic lesion of the thyroid carcinoma resembling MFC consisted of TG‐ positive cells and neighboring calcitonin (CT)‐positive cells. However the primary lesion exhibited the typical features of papillary carcinoma except for the presence of a small lesion which stained negatively for both TG and CT. The two types of tumor were not intermingled in a single tumor. These cases of thyroid carcinoma resembling MFC have a possibility of being MFC. However they should not be classified as MFC because lymph node metastasis or the coexistence of medullary carcinoma and follicular carcinoma in their primary lesion was not proved.

Mixed Medullary-Papillary Carcinoma of the Thyroid with Lymph Node Metastases: Report of a Case

“…9,11,12 Interestingly, a number of cases of thyroid cancer with a mixed medullary and follicular pattern have been reported. [3][4][5][6][7][8][9][10][11][12][13][14][15] Many investigators believe that mixed medullary and follicular carcinoma of the thyroid is derived from neoplastically transformed uncommitted stem cells with the capacity to differentiate into tumor components with morphological and histochemical 16 suggested that the follicular and medullary components in mixed medullary and follicular carcinoma are not derived from a single progenitor cell, because they observed different patterns of RET proto-oncogene mutation, LOH, and X-chromosomal inactivation (clonality) is seven tumors. According to Matias-Guiu, 17 confirmation of the so-called "hostage hypothesis" would require the unknown tropic factors necessary for the stimulation of follicular cells, as well as the detection of these substances in the medullary thyroid cells of mixed medullary and follicular carcinomas and their absence in classical medullary thyroid cells.…”

Goblet cell carcinoids and other mixed neuroendocrine/nonneuroendocrine neoplasms

“…MMFC are very rare tumors, accounting for less than 0.2% of all thyroid tumors [34,56]. As for conventional medullary carcinoma, MMFC may arise as sporadic tumors, in the vast majority of reported cases, or associated with MEN2 syndrome [38,43,47,55], both type 2A and type 2B.…”

Mixed medullary and follicular cell thyroid carcinoma in a dog

“…Medullary carcinomas comprise 5–10% of all thyroid carcinomas in humans, and only 3–5% of these neoplasms (~0.15% of all thyroid tumors) display mixed features, having a follicular or papillary carcinoma component in the primary medullary carcinoma or in the metastases, or in both. 1,3,4,8,10 Mixed medullary-follicular thyroid carcinoma have not been reported in dogs, to our knowledge, and the WHO International Classification of Tumors of Domestic Animals does not include this entity. 2…”