|Year : 2021 | Volume
| Issue : 2 | Page : 82-83
Cartilaginous metaplasia: A unique microscopic finding in multinodular goiter
Department of Pathology and Laboratory Medicine, All India Institute of Medical Sciences, Bibinagar, Telangana, India
|Date of Submission||16-Nov-2021|
|Date of Acceptance||15-Jan-2022|
|Date of Web Publication||21-Mar-2022|
Dr. Seetu Palo
Department of Pathology and Lab Medicine, All India Institute of Medical Sciences, Hyderabad Metropolitan Region, Bibinagar - 508 126, Telangana
Source of Support: None, Conflict of Interest: None
Cartilaginous metaplasia in multinodular goiter is an extremely rare finding and this study is only the second case report describing the same. A 54-year-old female presented with thyroid swelling of 3 years' duration and underwent total thyroidectomy. Microscopy revealed the features of multinodular goiter with areas of cystic change, hemorrhage, Hurthle cell metaplasia, lymphoid aggregates, and sclerosis along with tiny islands of mature cartilage formation.
Keywords: Cartilage, goiter, metaplasia, thyroid
|How to cite this article:|
Palo S. Cartilaginous metaplasia: A unique microscopic finding in multinodular goiter. Thyroid Res Pract 2021;18:82-3
| Introduction|| |
Nodular goiter is the most common form of thyroid disease, exhibiting a wide variety of degenerative changes., However, heterotopic cartilage formation in goiter is of very rare occurrence, with only a single case reported till date, to the best of author's knowledge. Here, another such case of sporadic multinodular goiter with cartilaginous metaplasia is presented.
| Case Report|| |
A 54-year-old female presented with an anterior neck mass that had been present for 3 years. The patient had no other clinical or local compressive symptoms. Her complete blood counts and thyroid hormone levels were within the normal limits. She had no significant past medical history. Ultrasonographic examination revealed an enlarged thyroid gland with multiple iso/hyperechoic nodules in both the lobes, largest measuring 19 mm. No internal macro/micro-calcifications were detected. Fine-needle aspiration cytology was suggestive of nodular goiter (Bethesda category II). A total thyroidectomy was performed. On gross examination, the thyroid gland was enlarged, soft-to-firm in consistency and nodular. Right lobe, left lobe and isthmus measured 6 cm × 5 cm × 3.5 cm, 5.5 cm × 4.5 cm × 3.5 cm, and 3.5 cm × 2.5 cm × 2 cm, respectively. Serial sectioning revealed a variegated appearance consisting of colloid-filled nodules along with tan-brown solid, hemorrhagic, cystic, and fibrotic areas. Microscopically, it was consistent with multinodular goiter with secondary changes. There were multiple nodules comprising of variably sized follicles, filled with colloid and lined by benign follicular cells. Areas of cystic change, hemorrhage, collections of hemosiderin-laden macrophages, focal Hurthle cell change, lymphoid aggregates with germinal center formation, and sclerosis were present. Two discrete lobules of mature hyaline cartilage were found [Figure 1]. There was no evidence of calcification or ossification. Postoperatively, the patient was put on thyroxin replacement dose, and she was euthyroid on her last follow-up visit.
|Figure 1: Variably-sized benign thyroid follicles along with well-demarcated, discrete islands of mature hyaline cartilage (arrow) (original magnification × 200, hematoxylin and eosin)|
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| Discussion|| |
Hemorrhage, calcification, fibrosis, and cystic degeneration are the well-known secondary changes that occur in cases of multinodular goiter. Other microscopic features that can be encountered are infarction, lymphoid aggregates, granulomatous reaction with formation of foreign body giant cells, cholesterol clefts, mucin, and squamous metaplasia.,,, Recently, many cases of osteoid differentiation with or without extramedullary hematopoiesis have been reported in association with nodular goiter as well in neoplastic thyroid nodules. [1,6-10] However, heterotopic cartilage formation is an exceedingly rare finding, both in nonneoplastic and neoplastic thyroid lesions.,
In the present case, the focus of cartilaginous metaplasia was tiny and grossly in-evident, similar to the only other such case reported by Pittaro et al. It came across as an incidental finding during microscopy. In routine practice, extensive sampling of thyroidectomy specimens is not performed in cases of multinodular goiter, unless there are some suspicious gray-white solid areas upon thorough gross inspection. Areas of osseous metaplasia, if any, appear distinctly hard or gritty and hence are often sampled. On the other hand, tiny foci of cartilage are likely to be missed on gross examination, owing to its' resemblance to solidified colloid in color and consistency. This might be a contributing factor for meager number of documented cases of chondroid metaplasia in thyroid lesions in comparison to osteoid metaplasia.
The histogenesis of cartilage in nodular goiter remains unclear. Virchow hypothesized that osteoblasts, which give rise to bone formation in thyroid nodules, are modified fibroblasts. Similarly, it is quite possible that chondroblasts too originate from fibroblasts by metaplasia. Basbug et al. demonstrated a significantly higher expression of bone morphogenetic protein-2 (BMP-2) in calcified thyroid tissue, thereby emphasizing the role of BMPs in inducing ossification in thyroid nodules. BMP-2 plays a vital part in chondrogenesis as well, by promoting chondrocyte proliferation and maturation during endochondral bone formation. Hence, it seems plausible that chondroid and osteoid differentiation in thyroid lesions occurs as a sequential process, orchestrated by various BMPs and possibly other extracellular matrix proteins.
In conclusion, this case establishes mature cartilage formation as a rare histopathological finding and adds it to the constellation of other changes found in nodular goiter.
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Conflicts of interest
There are no conflicts of interest.
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