A Case of Parathyroid Adenocarcinoma and Hyperparathyroidism, When 'CRAB' Symptoms Are Not due to a Plasma Cell Myeloma

A previously well 49-year-old patient presented to our hospital with symptomatic hypercalcaemia complaining of polyuria and polydipsia, as well as abdominal and lower back pain (serum/ionized calcium at 3.66 milli mole/l and 1.90 milli moles/l). At admission, he had a normocytic anemia (Hb, 99 g/L) and acute kidney injury (creatinine at 161 μM). His parathyroid hormone (PTH) levels were at 67.6 pico moles/l. A plain X-ray of the lumbar spine showed the presence of a lytic lesion in the L4 vertebrae. CT and MRI confirmed this to be a destructive lesion. A subsequent pan CT scan showed a 2.8 cm complex nodule in the left lobe of the thyroid posteriorly. Excisional biopsy of the resected mass was associated with an infiltrative cellular parathyroid neoplasm with solid and nested architectural growth pattern admixed with hemorrhage and focal calcifications. The tumor showed lymphovascular and perineural invasion. At the time of workup and despite the absence of a positive SPEP/UPEP, a bone marrow biopsy was requested to rule out multiple myeloma. His normocellular bone marrow biopsy showed marked paratrabecular fibrosis and extensive bony remodelling but no metastatic invasion. The diagnosis of a metastatic parathyroid carcinoma was made. He is subsequently considered for palliative radiotherapy to the primary tumor bed and the lumbar spine. In addition, a role for immunotherapy with ipilimumab and nivolumab in context of clinical trials is envisioned and he is being considered for enrollment.