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|Year : 2010 | Volume
| Issue : 1 | Page : 35-36
Diffuse lipomatosis of thyroid with hyperthyroidism
PV Pradeep1, R Kumar1, M Ragavan1, BA Ramakrishna2
1 Department of Endocrine Surgery, Narayana Medical College & Super specialty Hospitals, Chinthareddypalem, Nellore, Andhra Pradesh, India
2 Department of Pathology, Narayana Medical College & Super specialty Hospitals, Chinthareddypalem, Nellore, Andhra Pradesh, India
|Date of Web Publication||12-Apr-2010|
P V Pradeep
Department of Endocrine Surgery, Narayana Medical College & Super specialty Hospitals, Chinthareddypalem, Nellore, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Pradeep P V, Kumar R, Ragavan M, Ramakrishna B A. Diffuse lipomatosis of thyroid with hyperthyroidism. J Postgrad Med 2010;56:35-6
Although the thyroid gland contains hardly any adipose tissue, diffuse lipomatosis of the thyroid (DLT)  and thyroid adenolipomas  have been described, albeit rarely. All such reported cases had a euthyroid status. , We report a case of DLT with hyperthyroidism which has not been reported so far in English literature.
A 40-year-old hyperthyroid female presented with a soft multinodular goiter involving both the lobes. There was no clinical evidence of any other swelling in the neck or elsewhere in the body. Thyroid profile revealed TSH of 0.1(0.3-4.5 IU/ml), elevated FT4 2.4(0.8-2.0 ng/dl), and FT3 7.2 (1.4-4.2 pg/ml). Serum thyroperoxidase antibody (TPO) and anti thyroglobulin antibodies were negative. Ultrasound (USG) of the thyroid gland showed left lobe to be 5 × 2.2 × 2 cm and right lobe 7 × 4.2 × 3.5 cm in size, respectively, along with multiple nodules in both lobes. Some nodules showed cystic components with septations. No cervical nodes were seen. Euthyroidism was achieved with Carbimazole 30 mg and Propranolol 40 mg daily. FNAC revealed colloid goiter. During surgery, the thyroid was unusually soft and friable making it difficult to handle. This resulted in tearing of the gland at multiple sites with greater than usual blood loss. The entire gland had ragged margins after dissection suggestive of its fragile nature [Figure 1]. The histopathology revealed DLT [Figure 2]. Grossly the gland was yellowish brown in colour and had fatty appearance on cut section [Figure 3]. Multiple sections from both lobes revealed thyroid follicles of varying sizes lined by cuboidal epithelium with colloid, fibrosis and hemorrhage. Most of the thyroid stroma was replaced by adult adipose tissue, few areas show fibrous septa separating the adipose tissue from adjacent thyroid tissue. However, there were no amyloid deposits or any evidence of malignancy. The recovery was uneventful.
Lipoma an ubiquitous tumour becomes apparent by 40-60 years of life.  Normally, the fat tissue in the thyroid gland is restricted to the subcapsular region along the vessels and the fibrous septa.  Fat containing lesions of the thyroid has been divided as lesions containing macroscopic fat and those containing intracellular fat vacuoles. The differential diagnosis in the former includes DLT, adenolipoma, amyloid goiter, lymphocytic thyroiditis, liposarcoma and intrathyroidal thymic and parathyroid lipoma.  DLT is a rare entity, initially reported by Dhayagude in 1942.  In contrast to all other previously reported cases with DLTs that were euthyroid, our patient had hyperthyroidism. However, we do not propose that hyperthyroidism was causally related to DLT.
In DLT, the FNAC reveals abundant fat cells between normal follicles without any signs of hyperplasia and malignancy.  Our pathologist retrospectively did confirm that there were abundant fat cells in the FNAC smear; however, there are no definite guidelines to make a diagnosis of DLT by FNAC. CT scan, MRI and USG have been shown to be effective in the preoperative diagnosis of such fatty lesions.  CT reveals low attenuation components with negative Hounsfield units.  In a suspected case of DLT due to the softness of the gland, both FNAC and CT can confirm the diagnosis preoperatively. , However, CT is not indicated in all cases of thyroid swellings and it cannot be recommended just to pick up a rarest of the rare entities. Unlike in the usual toxic MNG where the role of radio ablation has been established, its role has not been studied in DLT. We feel that those with diffuse lipomatosis interspersed with hyper functioning thyroid follicles are less likely to respond to radio iodine ablation therapy and hence surgery forms the obvious mode of treatment; however, this needs to be substantiated with more literature evidence. We undertook surgical intervention mainly for cosmetic purposes. During surgery, we found that even the minimum traction to rotate the gland medially resulted in tearing and excess oozing causing difficulty in identifying the parathyroids and recurrent laryngeal nerves. However, there was no postoperative hypocalcemia or voice change. Among the lesions which come in the differential diagnosis of fatty swellings in the thyroid, the adenolipomas can be easily differentiated from DLT because the former appear as focal nodules within an otherwise normal gland.  Differentiating adenolipomas from intrathyroidal parathyroid lipoadenoma may be difficult and may need immunohistochemistry.  However, liposarcoma of the thyroid is rare, the rapid clinical course and local invasion suggests the diagnosis  Rarity of DLT makes the preoperative diagnosis difficult. USG, CT or FNAC can diagnose DLT only in presence of high degree of clinical suspicion. Rarely, it can be associated with hyperthyroidism. Surgery should be meticulous and with caution in view of friability of the gland and risk of excessive bleeding.
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[Figure 1], [Figure 2], [Figure 3]