A 30-year-old man was referred to our Department of General Surgery for evaluation of persistent hypercalcemia. History revealed a 10-year history of constipation, recurrent episodes of renal colic, chronic fatigue, dyspepsia and hypercalcemia of unknown etiology. Eight months prior, in a different hospital, the patient underwent neck ultrasound that revealed a hypoechogenic mass located under the left thyroid lobe with an intense uptake during Tc-99m-sestamibi parathyroid scintigraphy. Subsequent surgical neck exploration had been unsuccessful.
Endocrinologic family history was uneventful; the patient's parents and two brothers had normal serum calcium levels and his one child was healthy. He did not take vitamin supplements, lithium or thiazide diuretics. Physical examination was negative, motor strength and reflexes were normal. Renal scan showed bilateral nephrolithiasis, and orthopantomography revealed signs of bone resorption at the jaw level.
Laboratory tests on admission showed hypercalcemia (12.7 mg/dL), hypophosphatemia (0.90 mg/dL), normal intact-PTH level (41.0 pg/mL) and an increase in 1,25-dihydroxycholecalciferol level (148.7 pg/mL). Urine biochemistry revealed elevated 24-hour urine calcium excretion (559 mg/24 h), phosphate clearance (57.8 mL/min) and urinary calcium to creatinine clearance 2 hours (0.30 mg/mg creatinine), whereas urinary cAMP was normal (3.9 nmol/100 mL glomerular filtrate). Thyroid and kidney function tests were within normal limits; tumor markers and blood tests for metabolic abnormalities were negative.
Neck ultrasound was not significant; thorax CT scan revealed an encapsulated mass of 3 cm in the upper anterior mediastinum located behind the sternoclavicular junction (Figure ). Tc-99m sodium pertechnetate/Tc-99m-sestamibi parathyroid dual-phase scintigraphy with subtraction image technique revealed the mass to be an ectopic parathyroid adenoma at the level of the left sternoclavicular junction (Figure ).
Multislice CT revealed an encapsulated mass of 3 cm in the upper anterior mediastinum behind the sternum-clavicular joints, with marked peripheral enhancement (arrow).
Figure 2 Tc-99m-sestamibi Tc-99m sodium pertechnetate substraction image showed an area of intense uptake below the inferior pole of the left thyroid lobe, in the upper mediastinum, in the left median position and normal thyroid with homogenous radiopharmaceutical (more ...)
These data confirmed the hypothesis of parathyroid-dependent hypercalcemia. A radioguided adenoma resection through a collar reincision was performed. One hour prior to surgery, 50 MBq of Tc-99m – sestamibi was injected intravenously; in the operating room, the gamma probe (MR-100, 11C, Pol.hi.tech) was used to identify the following: in vivo localization of the cutaneous projection of the adenoma; ex vivo uptake of the 3.2 cm excised ectopic adenoma and, lastly, to confirm removal of the pathologic gland, on the "background" operated area. A biopsy of the right inferior parathyroid, though apparently normal, was performed. Intraoperative PTH was reduced by more than 50% compared to the normal preoperative level.
Histologically, the tumor consisted of cords and small nests of cells with large granular eosinophilic cytoplasm with round to oval nuclei; the final diagnosis was oxyphil adenoma. Tumor cells were immunohistochemically positive for PTH (DakoCytomation; dilution 1:100; mouse) and PTHrP (Acris; 1:200; rabbit) antigens (Figure ). The gland biopsy was normal.
Strong and diffuse expression of PTHrP in the oxyphil adenoma (200 × original magnification).
Serum calcium level was normal in the immediate postoperative period (8.9 mg/dL) and 1, 6 and 12 months after surgery (8.6-8.9-8.4 mg/dL, respectively), with unchanged PTH within normal limits (11 pg/mL, day 1 after surgery; 9.4-13.0-17.0 pg/mL in 1, 6 and 12 months after surgery, respectively).
Recovery was uneventful and the patient was discharged 24 hours after the operation.