The pathologist's role in familial nonmedullary thyroid tumors

Inherited Follicular Epithelial-Derived Thyroid Carcinomas: From Molecular Biology to Histological Correlates

Cancer derived from thyroid follicular epithelial cells is common; it represents the most common endocrine malignancy. The molecular features of sporadic tumors have been clarified in the past decade. However the incidence of familial disease has not been emphasized and is often overlooked in routine practice. A careful clinical documentation of family history or familial syndromes that can be associated with thyroid disease can help identify germline susceptibility-driven thyroid neoplasia. In this review, we summarize a large body of information about both syndromic and non-syndromic familial thyroid carcinomas. A significant number of patients with inherited non-medullary thyroid carcinomas manifest disease that appears to be sporadic disease even in some syndromic cases. The cytomorphology of the tumor(s), molecular immunohistochemistry, the findings in the non-tumorous thyroid parenchyma and other associated lesions may provide insight into the underlying syndromic disorder. However, the increasing evidence of familial predisposition to non-syndromic thyroid cancers is raising questions about the importance of genetics and epigenetics. What appears to be "sporadic" is becoming less often truly so and more often an opportunity to identify and understand novel genetic variants that underlie tumorigenesis. Pathologists must be aware of the unusual morphologic features that should prompt germline screening. Therefore, recognition of harbingers of specific germline susceptibility syndromes can assist in providing information to facilitate early detection to prevent aggressive disease.

Thyroid Pathology Findings in Cowden Syndrome: A Clue for the Diagnosis of the PTEN Hamartoma Tumor Syndrome

OBJECTIVES

PTEN hamartoma tumor syndrome (PHTS) is a hereditary disorder caused by germline inactivating mutations of the PTEN gene. PHTS includes Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome. We describe how the peculiar pathologic and immunohistochemical thyroid features lead pathologists to suggest PHTS.

METHODS

A 28-year-old white Spanish woman had a multinodular goiter. Total thyroidectomy was performed after fine-needle aspiration biopsy. Microscopic, immunohistochemical, and molecular analyses of the thyroid lesions were realized.

RESULTS

The thyroid was multinodular, showing one papillary microcarcinoma, five follicular adenomas, three adenolipomas, 46 tiny adenomatous nodules (microadenomas), scattered foci of adipose tissue, and lymphocytic thyroiditis. Tumors were positive for thyroglobulin, thyroperoxidase, pendrin, cyclin D1, and p27 but negative for calcitonin and PTEN. A germline heterozygous deletion of one adenine at nucleotide 827 in exon 8 of the PTEN gene was confirmed. No BRAF, NRAS, or KRAS somatic mutations were detected in the papillary microcarcinoma, follicular adenoma, adenolipomas, or microadenomas. Negativity for PTEN was also found in the colonic tubulovillous adenoma and the storiform collagenoma.

CONCLUSIONS

Pathologists play a crucial role in recognizing pathologic thyroid findings associated with PHTS for selecting patients for genetic testing.

Cribriform-Morular Variant of Papillary Thyroid Carcinoma in an 8-Year-Old Girl

The description of the histological features and the immunohistochemical and molecular analyses of a case of cribriform-morular variant of papillary thyroid carcinoma in an 8-year-old girl with a family history of adenomatous polyposis is presented. The neoplasm was multifocal and bilateral, with a mixed pattern of solid, trabecular, and morular areas. The neoplasm showed angioinvasive behavior, extracapsular infiltration with extension to the perythyroidal muscles, and lymph node metastases. Tumor cells were positive for CAM 5.2, cytokeratins 5/6, TTF-1, HBME-1, galectin-3, and β-catenin. In addition, the molecular tests did not reveal BRAF mutations, RET/PTC rearrangement, APC mutation, or KRAS mutation.