Heterotopic Ossification with Intrathyroidal Extramedullary Hematopoiesis in Multifocal Papillary Thyroid Carcinoma: Histopathological Findings and Literature Review.

Abstract

In recent decades, there has been an increase in the identification of thyroid nodules, both benign and malignant, due to the rise in imaging studies and complementary tests. Among thyroid gland tumors, papillary thyroid carcinoma (PTC) stands out as the most prevalent. Degenerative changes, mainly in the form of nodular goiter, have been recorded, occasionally including areas of calcification and, more rarely, ossification; although the latter seldom progresses to calcinosis. Ectopic bone formation, known as osseous metaplasia, is a rare phenomenon in the thyroid gland, even more so when associated with extramedullary hematopoiesis (EMH), characterized by the presence of hematopoietic elements outside the bone marrow. We present the first documented instance in our country of a patient diagnosed with malignant thyroid nodule, specifically PTC, exhibiting areas of heterotopic ossification with EMH on histopathological examination of the surgical specimen. A possible relationship between heterotopic ossification, EMH, and PTC is suggested. Various growth factors such as bone morphogenetic proteins (BMPs), specific BMP subtypes, and associated receptors could play a crucial role in initiating and developing ectopic bone formation in the context of PTC. However, further research is needed to fully elucidate its clinical significance and impact on the therapeutic management of these patients.