Missed diagnosis of lymphoma presenting with humoral hypercalcemia of malignancy due to cessation of oncological workup after negative computed tomography scans

Malignancy is the most common cause of hypercalcemia among hospitalised patients and is frequently caused by elevations in parathyroid hormone-related peptide (PTHrP). The most common PTHrP-producing cancers are carcinomas of the head, neck and lung. Hypercalcemia can be the presenting sign of cancer and, in these cases, solid tumours are usually discovered on CT scan. In rare cases, lymphoma may also present with hypercalcemia. CT scan is less sensitive for lymphoma than for most solid tumours and the diagnosis may be missed. We present the case of a 69-year-old woman who presented with hypercalcemia in the setting of severe weight loss and elevated PTHrP. Oncological workup was stopped after unrevealing CT scans and an underlying lymphoma was missed. Our case emphasises the need for a comprehensive oncological workup for patients with unexplained hypercalcemia and elevated PTHrP, even when CT scans are unrevealing.

Ectopic Intact PTH Secretion Causing Humoral Hypercalcemia of Malignancy

Background: Tumor-generated ectopic intact PTH is difficult to diagnose and should be suspected in patients with apparent primary hyperparathyroidism but with normal parathyroid glands. Clinical Case: A 72-year-old man presented with symptoms of hypercalcemia including generalized weakness, polyuria, and polydipsia. Initial labs were consistent with primary hyperparathyroidism: calcium 12.1 mg/dL (n 8.6–10.3 mg/dL, albumin-corrected 12.5 mg/dL), intact PTH (iPTH) 115.6 pg/mL (n 10–65 pg/mL), low normal 25-OH vitamin D (25 ng/mL, n 25–100 ng/mL), and relatively high normal 1,25 dihydroxyvitamin D (52 pg/mL, n 18–78 pg/mL). 24-hour urine calcium was 381 mg/day (n 100–300 mg/day) and PTHrP was 1.6 pmol/L (n <4.2 pmol/L). Neck ultrasound demonstrated a 0.5 x 1 cm hypoechoic mass near right thyroid inferior pole, though sestamibi SPECT/CT scan did not reveal scintographic evidence of a parathyroid adenoma. He underwent subtotal parathyroidectomy with largest excised gland weighing 0.262 grams. The left inferior parathyroid gland appeared normal intraoperatively, thus was clipped and left in place. PTH decreased from 194 pg/mL to 98 pg/mL postoperatively. Pathological examination revealed three normocellular parathyroid glands with enlargement of only the right superior gland. Venous sampling of the parathyroid vasculature failed to identify the source of autonomous iPTH post operatively. Due to refractory hypercalcemia, cinacalcet was initiated. However, hypercalcemia as high as 12.6 mg/dl and hyperparathyroidism to 672 pg/mL persisted despite dose escalation. He eventually received pamidronate with subsequent transition to denosumab due to declining renal function. A 68Ga DOTATATE scan was performed to locate occult ectopic parathyroid, which reported multiple foci of presumed somatostatin receptor expression involving the liver and intra-abdominal lymph nodes without significant uptake in the neck concerning for metastatic disease. Liver lesion biopsy was consistent with pancreato-biliary adenocarcinoma. Surprisingly, the biopsy was negative for iPTH and neuroendocrine tumor markers on staining/immunohistochemistry. Given his poor prognosis and multiple comorbidities, the patient opted not to pursue any further workup or therapy for his malignancy. Conclusion: Occult malignancy should be suspected for a patient with persistent hyperparathyroidism after parathyroidectomy. Treatment of the malignancy may lead to an improvement in hypercalcemia and iPTH levels. Employment of iPTH mRNA testing or intra-abdominal venous sampling to prove ectopic iPTH secretion would be ideal, as iPTH staining could be falsely negative. Further testing was not completed as the patient declined further evaluation.

1-25OH2D Mediated Hypercalcemia Secondary to DISR From Immune Checkpoint Inhibitors

Background: Drug induced sarcoid like reactions (DISR) have recently been described as a potential consequence of immune checkpoint inhibitor therapy. However, hypercalcemia associated with DISR has not been reported. Clinical Case: A 72 year old male presented with metastatic melanoma. He initiated therapy with Ipilimumab/Nivolumab (Ipi/Nivo). Three weeks after his first cycle he developed symptomatic hypercalcemia (calcium 14.4 mg/dL), and acute kidney injury (creatinine 3.45mg/dL), PTH 12 pg/mL, 25OHD 51, and PTHrp 0.5. He received IV fluids and IV bisphosphonates and calcium normalized to 9.1 mg/dL and creatinine 1.85 mg/dL. His Ipi/Nivo were stopped due to concern for neurotoxicity. He subsequently switched to Q3week Pembrolizumab (Pembro) and after 2 infusions, he again developed hypercalcemia (calcium 11.8 mg/dL). FDG PET demonstrated a complete radiographic response. Labs showed a 1,25OH2D of 103 pg/mL (reference range 19.9–79.3 pg/mL), PTH of 4 pg/mL and calcium of 11.4 mg/dL. He was treated with prednisone 20 mg QD. After 9 days on prednisone, 1,25OH2D was 26 pg/mL and calcium 9.4 mg/dL. He took prednisone for 3 weeks total. Repeat labs off prednisone for one week were 1,25OH2D of 38 pg/mL and calcium 9.1 mg/dL. He continued on Pembro. After being off steroids for 5 weeks, he developed body aches and swelling of the hands. 1,25OH2D increased to 100 pg/mL and calcium to 10 mg/dL. He restarted prednisone and stopped Pembro. Labs one month later showed a 1,25OH2D of 45 pg/dL while still on prednisone 10 mg qd and a normal calcium in the mid 9’s. Follow up FDG PET showed hypermetabolic bilateral hilar and mediastinal lymphadenopathy not seen on previous imaging. Ultrasound-guided lymph node biopsy revealed granulomatous lymphadenitis. He was diagnosed with DISR, secondary to immunotherapy with checkpoint inhibitors. He continues on prednisone 10 mg per day and calcium and 1,25OH2D levels have remained normal. Conclusion: This is the first case of 1,25OH2D mediated hypercalcemia as a consequence of DISR induced by immune checkpoint inhibitor therapy. Hypercalcemia in the setting of malignancy is more commonly due to humoral hypercalcemia of malignancy from PTHrp or bone metastasis, but DISR needs to be a consideration in persons with hypercalcemia on immune checkpoint inhibitor therapy, with elevated 1,25OH2D levels and low PTH and PTHrp levels.

Leukocytosis and PTHrP-Mediated Hypercalcemia: Ominous Signs in an Indolent Thyroid Nodule

Introduction/Background: Anaplastic thyroid cancer is a rare thyroid malignancy with a bad prognosis. There are few systemic markers, as thyroglobulin is not usually synthesized in these poorly differentiated malignancies. Clinical Case - Diagnostic Evaluation, Treatment, and Follow Up: A 70-year old man presented in 2016 with a right thyroid nodule, slowly growing since 2012. The nodule was 10cm on neck CT and ultrasound showed a hyperechoic mass with central hypoechoic area, and coarse calcifications. Fine needle biopsy showed a follicular neoplasm. By 2019, neck CT showed enlargement of the nodule to 13 cm. Repeat thyroid biopsy was benign. Lobectomy was recommended due to size but not performed. In 2020, he developed neck discomfort and painful thigh swelling. WBC was significantly elevated at 27,000 (4000-10000) /mm3. Ultrasound showed no evidence of necrosis or abscess in the nodule. WBC rose progressively to 96,000/mm3 (ANC 94,200). CT chest showed further enlargement of the thyroid mass, a soft tissue shoulder mass and lung nodules suspicious for metastases. Laryngoscopy revealed a distorted larynx from external compression, and possible vocal-fold involvement (motion impairment) without airway compromise. Biopsy of the shoulder mass, lung nodule, and thigh masses all showed metastatic anaplastic thyroid cancer. Full infectious disease evaluation and molecular testing for BCR-ABL and JAK2 mutations were negative. Thus, leukocytosis was determined to be reactive in the setting of malignancy. Serum calcium of 14.7 mg/dL (8.5 - 10.6mg/dL) prompted hospital admission. Bone metastases were not visible on imaging. Hypercalcemia was treated effectively (to 8.3mg/dL) with IV fluids, calcitonin and IV bisphosphonates. Workup revealed suppression of PTH to 4 pg/mL (15-65 pg/mL) and low 25 Vitamin D of 21 ng/mL (30-80ng/L). Subsequently PTHrP was elevated at 53.4 pmol/L (<2.3pmol/L) and 1,25 Vitamin D inappropriately normal at 48.9 pg/mL (20- 79.3pg/mL), suggested humoral hypercalcemia of malignancy. The patient declined further treatment beyond hospice care. Clinical Lesson/Conclusion: Significant, sudden leukocytosis and hypercalcemia prompted further evaluation of his long-standing apparently benign thyroid nodule leading to a diagnosis of anaplastic thyroid cancer. Presumably this mass had been a follicular thyroid cancer, misdiagnosed on cytology, that subsequently de-differentiated. There are uncommon reports of leukocytosis complicating anaplastic thyroid cancer, where elevated GCSF and IL-6 were noted. We suspect this same etiology here. Hypercalcemia is extremely rare other than one report of PTHrP-secreting anaplastic thyroid cancer. Thus, high, rising calcium and PTHrP levels may reflect level of disease activity in anaplastic thyroid cancer.

Development of a PTHrP Chemiluminescent Immunoassay to Assess Humoral Hypercalcemia of Malignancy

Background: Measurement of parathyroid hormone related peptide (PTHrP) is helpful in the diagnosis and clinical management of patients suspected of humoral hypercalcemia of malignancy (HHM). In these patients uncontrolled release of PTHrP by tumor cells is responsible for the hypercalcemia and PTH concentrations are typically suppressed. Objective: Develop a sensitive and specific assay for quantitation of PTHrP in plasma. Method: Calibrators (PTHrP 1-86) and samples (50uL) were incubated with an anti-PTHrP goat polyclonal acridinium ester labeled antibody. Complexes were transferred and incubated in a microplate coated with an anti-PTHrP polyclonal rabbit antibody. After washing, the acridinium ester generated signal, which is directly proportional to the amount of PTHrP in sample, was quantified. Results: In this assay PTHrp was stable for 24 hours ambient, 3 days refrigerated, 34 days frozen and through 3 freeze/thaws. Intra and inter-assay imprecision in EDTA plasma (~0.16-35.0 pmol/L) ranged from 2.2-8.6% and 5-15%, respectively. The limit of detection was 0.04 pmol/L and the limit of quantitation was 0.16 pmol/L (15% CV). The analytical measuring range was 0.39-50.5 pmol/L (slope of 1.07 and r2 of 0.99). Average spike recovery was 98% (range 85-108%). The assay was not affected by hemoglobin of ≤500 mg/dL, triglycerides of ≤2000 mg/dL, or bilirubin of ≤50mg/dL. No hook effect was noted up to 500 pmol/L. PTH (1-84) did not cross-react in the assay. C-terminal PTHrP(107-139), and N-terminal PTHrP(1-36) had no significant cross-reactivity (≤1.1%). Mid-PTHrP(38-94) had 8.3% cross-reactivity. Comparison with an in-house PTHrP assay (n=267) showed an r2 of 0.96, and slope of 2.25 by Passing-Bablok regression fit. The 97.5% reference interval for PTHrP (n=114) was ≤0.7 pmol/L, however a higher concentration (≤4.2 pmol/L) was identified as a more specific clinical cut-off. A retrospective clinical validation study showed that using ≤4.2 pmol/L resulted in a 91% clinical sensitivity and a 98% clinical specificity. Conclusion: We have developed an analytically and clinically sensitive and specific PTHrP immunoassay. A cutoff of ≤4.2 pmol/L is clinically useful in the evaluation of patients suspected of hypercalcemia of malignancy.

Hypercalcemia Associated with Extramammary Paget’s Disease

Hypercalcemia of malignancy occurs in up to one third of patients at some point during the course of their advanced stage. The majority of them is caused by humoral hypercalcemia of malignancy due to systemic secretion of parathyroid hormone–related protein (PTHrP) by tumor cells. Extramammary Paget’s disease is a slow-growing cutaneous malignancy commonly limited to the epidermis of the anogenital region, but rarely becomes invasive and metastatic to distant sites. Herein, we report a 70-year-old male patient with metastatic extramammary Paget’s disease. He consulted our hospital with altered consciousness and tumor in his genital area. Physical examination revealed erythematous plaque with a tumor on the scrotum and perineum. It was diagnosed as extramammary Paget’s disease (multiple liver metastases and multiple lymph node metastases by skin biopsy and image examination). Increases in serum-corrected calcium and PTHrP-intact levels (15.3 mg/dL and 66.1 pg/L, respectively) were confirmed. PTHrP immunohistochemistry showed positive staining in the tumor cells. We diagnosed humoral hypercalcemia of malignancy. We treated hypercalcemia with saline, furosemide, zoledronic acid, and elcatonin. Regarding the local control of the tumor, 30 Gy/10 Fr electron beam therapy was performed. However, treatment with zoledronic acid was only temporally effective to correct hypercalcemia, and an increased serum calcium level developed again. Concurrently, the liver metastases were rapidly enlarged, and his general condition gradually deteriorated. The patient died on day 55. When patients with extramammary Paget’s disease show unconsciousness, serum calcium level should be measured and PTHrP-producing tumor distinguished.

When CKD-MBD is not just CKD-MBD, a case of humoral hypercalcemia of malignancy in a dialysis patient

Patients on maintenance hemodialysis have dysregulations of calcium and phosphorus homeostasis which results in a plethora of mineral and bone pathologies. Management is typically focused on maintenance eucalcemia and limiting hyperphosphatemia while avoiding extremes of intact parathyroid hormone. Hypercalcemia in this setting is often iatrogenic. We present a case of humoral hypercalcemia of malignancy initially thought to be iatrogenic due to mineral bone management and discuss the overlap of management of hypercalcemia and management of mineral bone disease in end stage kidney disease. We highlight the relationship between malignancy and end stage kidney disease and the increased risk of hypercalcemia associated with malignancy.