A 26-year-old man presented with a history of low back pain for six months and a history of right knee pain and swelling for one month, which had increased in the past week
Radiographs of the right knee, pelvis, and lumbar spine demonstrated diffuse osteopenia. A well-defined, multilocular, lytic lesion with a narrow zone of transition and no evident matrix mineralization was seen in the proximal epiphysis and metaphysis of the tibia (Figure 1,2). Multiple well-circumscribed lytic lesions were seen in the pelvic bones, epiphysis of both femoral heads, and left greater trochanter (Figure 3). Mild sclerosis of the endplates in the lumbar vertebrae was noted (Figure 4, 5).
MRI of the knee (Figure 6,13) was performed, which demonstrated a complex multiloculated heterogeneously enhancing solid-cystic lesion with multiple fluid-fluid levels. There was cortical breach posteriorly with extension of the lesion into the adjacent soft tissue. Multiple heterogeneously enhancing T1 hypointense, T2 hyperintense lesions were seen in the distal femur and fibula.
Neck ultrasonography (Figure 14,15) revealed a solid, hypoechoic nodule posterior to the left lobe of the thyroid with a peripheral feeding vessel and rim vascularity. The patient had elevated PTH level-1148.4 pg/ml (normal value-10-55 pg/mL). Fine needle aspiration of the lesion and 99mTc-sestamibi parathyroid scintigraphy was performed, which confirmed parathyroid hyperplasia.
Parathyroid adenomas are the most common cause of primary hyperparathyroidism. Brown tumors are focal bony lesions due to bone remodeling from primary or secondary hyperparathyroidism .
Symptomatically, patients suffering from hyperparathyroidism usually present with bone pain, renal stones, gastrointestinal and neurological complaints commonly recognized as “bones, stones, groans, and moans. Brown tumors present as slow-growing bone lesions that may cause pain or pathological fractures . When brown tumors are the initial manifestation of hyperparathyroidism, it can simulate a neoplastic process as in our case and cause lot of diagnostic dilemmas. Imaging plays an important role in characterizing these lesions and demonstrating other key diagnostic features of hyperparathyroidism. We should bear in mind that brown tumors should be considered in the differential diagnosis of multiple osteolytic lesions and guide clinicians with appropriate confirmatory investigations to avoid unnecessary and harmful interventions. Proper clinical history and laboratory investigations are important to arrive at the correct diagnosis .
Brown tumours are most commonly seen in the mandible, ribs, clavicle, and pelvis. They have variable radiological characteristics. They can be single or multiple, unilocular or multilocular, well-defined/ill-defined, osteolytic lesions, usually with bone expansion, can demonstrate bony destruction and be associated with pathological fractures/soft tissue involvement. The MRI appearance depends on the relative proportion of its components . The lesions may be solid, cystic, or mixed. Solid components are intermediate to low intensity on T1- and T2-weighted images, while the cystic components are hyperintense on T2-weighted images and may have fluid-fluid levels . There can be an enhancement of the solid component and septa.
Parathyroid adenomas are seen as an oval-shaped homogeneously hypoechoic lesion to the overlying thyroid gland . Doppler imaging commonly shows a characteristic extrathyroidal feeding vessel that enters the parathyroid gland at one of the poles. Internal vascularity is also commonly seen in a peripheral distribution in a characteristic arc or rim of vascularity . Color Doppler sonography of the overlying thyroid gland may show an area of asymmetric hypervascularity that may help to locate an underlying adenoma.99mTc-sestamibi scintigraphy and 4D CT’s can help confirm the presence and location of a parathyroid adenoma .
Pre-operative 99mTc sestamibi scan helps in accurately localizing the tumour and plays a greater role in localizing ectopic glands, which can help the surgeon in planning the surgical approach. Treatment of hyperparathyroidism is the first step in the management of brown tumours . After appropriate medical management or surgical resection of the parathyroid adenoma, brown tumours may regress, and almost all radiographic changes tend to return to normal. Our patient underwent resection of the parathyroid adenoma, and brown tumours had decreased in size on repeat imaging is done six months post-surgery.
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 Parathyroid Imaging: Technique and Role in the Preoperative Evaluation of Primary Hyperparathyroidism: American Journal of Roentgenology: Vol. 188, No. 6 (AJR) [Internet]. American Journal of Roentgenology. [cited 2020Apr2]. Available from: https://www.ajronline.org/doi/10.2214/AJR.06.0938
 Bubbly Lesions of Bone: American Journal of Roentgenology: Vol. 193, No. 2 (AJR) [Internet]. Ajronline.org. 2020 [cited 2 April 2020]. Available from: https://www.ajronline.org/doi/10.2214/AJR.09.2964
 Xie, C., Tsakok, M., Taylor, N. et al. Imaging of brown tumors: a pictorial review. Insights Imaging 10, 75 (2019). https://doi.org/10.1186/s13244-019-0757-z
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