A case of giant cell lesion as an initial feature of primary hyperparathyroidism is presented. A 55-year-old woman reported with a complaint of swelling and occasional pain in the upper-left posterior region with 2 months' duration. The diagnosis of a giant cell lesion with primary hyperparathyroidism was confirmed on the basis of radiological, biochemical, and histopathological investigative procedures. Palabras clave: brown tumor, giant cell lesion, ground-glass appearance, hyperparathyroidism, osteitis fibrosa generalisata, osteoporosis