Molecular alterations in hereditary and sporadic thyroid and parathyroid diseases

Advances and Updates in Parathyroid Pathology

Hyperparathyroidism is a common endocrine disorder characterized by elevated levels of parathyroid hormone and hypercalcemia and is divided into 3 types: primary, secondary, and tertiary. Distinction between these types is accomplished by correlation of clinical, radiologic, and laboratory findings with pathologic features. Primary hyperparathyroidism occurs sporadically in 85% of cases with the remaining cases associated with multiple familial syndromes. The pathologic manifestations of primary hyperparathyroidism include parathyroid adenoma, parathyroid hyperplasia, and parathyroid carcinoma. Recent advances in the understanding of the pathogenesis of parathyroid disease has helped to refine the diagnosis and classification of parathyroid lesions. The identification of multiple clonal proliferations in traditional multiglandular parathyroid hyperplasia has led to the adoption by the World Health Organization (WHO) of the alternate term of primary hyperparathyroidism-related multiglandular parathyroid disease. Additional nomenclature changes include the adoption of the term atypical parathyroid tumor in lieu of atypical parathyroid adenoma to reflect the uncertain malignant potential of these neoplasms. Clinical and morphologic features characteristic of familial disease have been described that can help the practicing pathologist identify underlying familial disease and provide appropriate management. Use of ancillary immunohistochemistry and molecular studies can be helpful in classifying parathyroid neoplasms. Parafibromin has proven useful as a diagnostic and prognostic marker in atypical parathyroid tumors and parathyroid carcinomas. This review provides an update on the diagnosis and classification of parathyroid lesions considering the recent advances in the understanding of the molecular and clinical features of parathyroid disease and highlights the use of ancillary studies (immunohistochemical, and molecular) to refine the diagnosis of parathyroid lesions.

Clinical and molecular genetics of parathyroid neoplasms

Primary hyperparathyroidism (HPT) results from the excessive secretion of parathyroid hormone from parathyroid tumours. While most HPT is sporadic, it is associated with a familial syndrome in a minority of cases. The study of these syndromes has helped define the pathophysiology of both familial and sporadic parathyroid neoplasms. Investigation of kindred with multiple endocrine neoplasia type 1 (MEN1) and the hyperparathyroidism-jaw tumour syndrome (HPT-JT) led to the discovery of the tumour suppressor genes MEN1 and HRPT2. We now recognise that somatic mutations in MEN1 and HRPT2 tumour suppressor genes are frequent events in sporadic parathyroid adenomas and carcinomas, respectively. Parathyroid tumours in the MEN2A syndrome result from mutational activation of the RET oncogene. The CCND1/PRAD1 oncogene was discovered by analysis of sporadic parathyroid tumours. Studies of familial isolated HPT and analysis of chromosomal loss and gain in parathyroid tumours suggest that other genes relevant to parathyroid neoplasia await identification.

Poorly differentiated thyroid carcinoma: a cytologic-histologic review

The term poorly differentiated thyroid carcinoma (PDTC) was first proposed in the 1980s, but it was not definitively recognized as a distinct pathologic entity until the most recent classification of endocrine tumors by the World Health Organization in 2004. More recently, as a result of discussions in Turin, Italy, in 2006, diagnostic criteria were made more specific by a consensus of expert thyroid pathologists. The histologic and cytologic aspects are detailed with particular attention to key features helpful in the diagnosis of PDTC, both in surgical pathology and in cytology-based studies. Histologically, insular, solid, and/or trabecular architecture, along with at least one of the following: convoluted nuclei, mitotic activity (>3/10 HPF), or tumor necrosis, are required for a diagnosis of PDTC. Cytologically, the combination of insular, solid, or trabecular cytoarchitectural pattern, single cells, high nuclear to cytoplasmic (N/C) ratio, and severe crowding are highly suggestive of PDTC. Most PDTCs are immunohistochemically positive for thyroglobulin and thyroid transcription factor 1 (TTF-1), and a subset is also positive for p53. On the molecular level, ras mutations are the most common finding. PDTCs are managed aggressively by total thyroidectomy, I, and in some cases, external beam radiotherapy.