Soft Tissue Metastasis of Parathyroid Carcinoma: Description of a Difficult Case

Abstract

Parathyroid carcinoma is an extremely rare cause of hyperparathyroidism. Histologic diagnosis may be challenging. DAB, male aged 66 was submitted to subtotal gastrectomy because of a localized gastric adenocarcinoma (intestinal type). A mild primary hyperparathyroidism was simultaneously found. Calcium oxalate nephrolithiasis was diagnosed 16 years before. Sonography revealed a nodular lesion in the right lower thyroid pole, while NMR showed a nodular lesion at the left lower thyroid pole. The sestamibi scan found a late image hyperfixation at the right lower pole. Bilateral inferior parathy roidectomy was performed and revealed on both sides adenoma and moderate nuclear polymorphism and no mitotic figures; on the left side a central cystic area was found. Clinical and biochemical cure apparently followed. Six months later a presumed unrelated nodular lesion in the right thigh muscular mass was removed and found to have numerous mitotic figures and immunoreactivity for PTH. A sestamibi scan showed marked hyperfixation in the right leg and PET-FDG-F 18 hyperfixated the right quadricipital area. There is evidence for a long standing disease since nephrolithiasis was found some years before. Long standing hyperparathyroidism and increased gastric acid secretion can lead to chronic gastritis, intestinal metaplasia and gastric adenocarcinoma. There is evidence for evolution along bilateral hyperplasia, adenoma and carcinoma since bilateral disease was present and left cystic nonfunctioning lesion was found. Most surprisingly a single metastatic lesion was later found in a very unusual location and this lesion was highly undifferentiated in sharp contrast with the primitive lesion.