Year : 2009 | Volume
: 52 | Issue : 3 | Page : 377--378
Osseous metaplasia and mature bone formation with extramedullary hematopoiesis in follicular adenoma of thyroid gland
Mohan Harsh1, Parul Dimri1, Nitin M Nagarkar2,
1 Department of Pathology, Government Medical College & Hospital, Chandigarh, India
2 Department of ENT and Head & Neck Surgery, Government Medical College & Hospital, Chandigarh, India
Department of Pathology, Government Medical College & Hospital, Sector 32, Chandigarh - 160 030
Follicular adenomas of the thyroid may be subjected to degenerative changes like hemorrhagic and cystic changes, fibrosis, and calcification. Mature bone formation is a rare phenomenon, but extramedullary hematopoiesis (EMH) has also been rarely reported in thyroid gland. The combination of mature bone formation and EMH is rarer and has been reported, in a single case report, in a multinodular goitre. We describe a case of follicular adenoma with histologically proven osseous metaplasia and mature bone formation with EMH in a middle- aged woman, which, to our knowledge, is the first case in English language literature.
|How to cite this article:|
Harsh M, Dimri P, Nagarkar NM. Osseous metaplasia and mature bone formation with extramedullary hematopoiesis in follicular adenoma of thyroid gland.Indian J Pathol Microbiol 2009;52:377-378
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Harsh M, Dimri P, Nagarkar NM. Osseous metaplasia and mature bone formation with extramedullary hematopoiesis in follicular adenoma of thyroid gland. Indian J Pathol Microbiol [serial online] 2009 [cited 2020 Aug 13 ];52:377-378
Available from: http://www.ijpmonline.org/text.asp?2009/52/3/377/54999
Follicular adenomas of the thyroid account for over 90% of benign neoplasms of the gland. Although they grow slowly they are, nonetheless, subject to degenerative changes like hemorrhagic and cystic changes, fibrosis, and calcification.  Mature bone formation in a thyroid nodule is a rare occurrence.  Extramedullary hematopoiesis (EMH) has been very rarely reported in a thyroid gland. ,, Of the reported cases, two patients had chronic myelofibrosis and one had chronic iron deficiency anemia. The detection of mature bone formation with a trabecular structure and the presence of EMH have been reported once, in a large nodule of a multi nodular goiter.  A follicular adenoma with extensive cartilaginous metaplasia has also been reported in literature.  However, a follicular adenoma with osseous metaplasia, mature bone formation and EMH, to our knowledge, has never been described.
A 50-year-old woman was investigated for a palpable lesion in the thyroid gland. She had a seven-year history of lump in front of the neck, which had recently increased in size and was causing difficulty in deglutition. She had no other compressive symptoms or any endocrinological manifestations to suggest thyroid abnormality. She had no history of previous irradiation to the head and neck region.
Her general examination was unremarkable. Palpation of the neck revealed a firm, non- tender swelling measuring approximately two cm in diameter in the left lobe of thyroid gland. The swelling moved with deglutition. There were no associated dilated veins and the local temperature was not raised. There was no cervical lymphadenopathy. Her complete blood counts and peripheral smear were normal. The thyroid hormone levels were also within normal limits.
Plain neck radiographs showed a calcified lesion in the left lower part of the neck, corresponding to the anatomical site of the palpable thyroid nodule. Ultrasound examination revealed a hyperechoic solid lesion measuring two cm in diameter in the left lobe of thyroid. The remaining thyroid gland was normal.
Fine needle aspiration cytology of the nodule could not be performed because of its stony hardness. An excision biopsy of the nodule was performed and submitted for histopathological examination. On gross examination, the resected nodule was spherical in shape and measured two cm in diameter. On cut section, it was encapsulated, grayish yellow in color and bony hard in consistency, with a rim of thyroid tissue at the periphery. Microscopic examination showed a circumscribed mass of osseous tissue enclosing fatty and cellular marrow with areas of calcification, surrounded by compressed thyroid tissue [Figure 1] and [Figure 2].
This case represents an unusual variant of follicular adenoma of the thyroid gland, characterized by osseous metaplasia, mature bone formation and EMH. The rarity of bone formation within thyroid lesions is highlighted by the fact that only two cases have been reported till date. ,
EMH or myeloid metaplasia is defined as the process of blood cell formation in sites other than those that are normally active.  It has been described in cases where there is increased demand for blood cells after severe and continuous hemorrhage, hemolysis in newborn or young children,  myelofibrosis and in patients with severe chronic disease of hematopoietic tissue such as chronic granulocytic leukemia, Hodgkin's disease, primary polycythemia, thalassemia, sickle anemia, pernicious anemia and hereditary spherocytosis.  It has also been described in chronic iron deficiency anemia.  The common sites of EMH are liver, spleen and lymph nodes.  However, it can occur almost in every organ. 
Thyroid gland, as a site of EMH has been described in only three reports. ,, Two of these patients had myelofibrosis, , and the third had chronic iron deficiency anemia secondary to long-term use methotrexate in the past for the treatment of psoriatic arthritis.  However, in the present case, no such abnormality which could possibly explain the cause for EMH, was found.
In conclusion, follicular adenoma of the thyroid gland, with osseous metaplasia, mature bone formation and EMH, as reported in the present case, is a rare entity, and to the best of our knowledge, based on the reviewed English language literature, has never been reported before.
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