Case of Recurrent Primary Hyperparathyroidism, Congenital Granular Cell Tumor, and Aggressive Colorectal Cancer.

We present the case of a 53-year-old African-American male with recurrent primary hyperparathyroidism (PHPT), multifocal benign granular cell tumor (GCT), and metastatic colon adenocarcinoma. PHPT was diagnosed on routine blood testing (ionized calcium, 1.66 [1.12-1.32] mmol/L; PTH 110 pg/mL, vitamin D-25-OH-D: 18 ng/mL; PTHrP: undetectable). Medical history was notable for 2 reoccurrences of PHPT with persistent disease after most recent parathyroidectomy. Lymph node (LN) dissection during this last surgery showed a 2-mm focus of poorly differentiated adenocarcinoma in 1/5 LNs. Additionally, the patient had a history of multifocal GCTs diagnosed at age 2 years. On examination, there were no Lisch nodules, axillary, or inguinal freckling, neurofibromas, or café-au-lait macules but a prominent abdominal wall nodule was noted. En bloc resection of a tumor in the tracheoesophageal groove, identified by sestamibi scan, and excision of 4.5-cm abdominal wall nodule showed both masses having histology consistent with GCT. Serum calcium and PTH did not decrease, indicating another unsuccessful surgery. Genetic testing was negative for germline variants in PHPT-associated genes, APC, or genes of RAS-MAPK signaling pathway. The LN finding of metastatic adenocarcinoma prompted an endoscopy and transbronchial biopsy leading to the diagnosis of widely metastatic colonic adenocarcinoma, eventually resulting in his death a year later. The source of the patient's persistent PHPT remained unidentified. This is the first case with coassociation of recurrent PHPT, multifocal GCT, and colon cancer. Whether the disparate tumors in this patient share common driver(s) remains unknown. Prospective surveillance of patients for similar associations may provide clues for a novel syndromic form of PHPT. Published by Oxford University Press on behalf of the Endocrine Society 2022.