MON-533 - A Rare Case of Combined Pheochromocytoma and Primary Diffuse Large B-Cell Lymphoma within A Giant Adrenal Tumor

Background: Pheochromocytoma is a rare catecholamine-secreting tumor originating from the adrenal medulla and classically associated with hypertension and adrenergic symptoms. “Silent” pheochromocytomas, lacking clinical manifestations, are increasingly recognized and may account for up 15% of cases. However, coexistence of a pheochromocytoma with primary lymphoma in an adrenal tumor is exceedingly rare. To the best of our knowledge only 4 similar cases have been reported in the literature so far.

Case: A 63-year-old Hispanic man with no regular medical care presented to the ER with progressive right-sided abdominal pain and a slowly growing palpable mass. CT abdomen/pelvis revealed a 27 cm heterogeneous multiloculated cystic abdominal mass with marked mass effect. A CT-guided biopsy (scant, predominantly necrotic tissue) was interpreted as EBV-positive large B-cell lymphoma, and he underwent six cycles of R-CHOP, including high-dose prednisone (100 mg daily), without hypertensive crisis. Due to lack of treatment response on subsequent imaging, a repeat CT-guided biopsy was performed that revealed a neuroendocrine neoplasm consistent with pheochromocytoma. The lesional cells stained diffusely positive for synaptophysin, chromogranin, GATA3 and negative for keratin stains. In addition, there was no loss of staining for SDHB. Biochemical evaluation revealed markedly elevated plasma metanephrines 12.0 nmol/L (0–0.49), plasma normetanephrine >50 nmol/L (0–0.89), plasma norepinephrine 14,888 pmol/L (reference 1,050–4,800), epinephrine 1,674 pmol/L (≤330) and dopamine 622 pmol/L (≤240). Cortisol excess was ruled out. An FDG PET -CT showed no evidence of distant metastatic disease. Preoperative preparation included alpha-adrenergic blockade with doxazosin, high salt and fluid intake, followed by beta-blockade, and metyrosine 4 days prior to surgery due to the large tumor size and marked biochemical activity. The patient underwent en-bloc resection of the right retroperitoneal mass and nephrectomy. Peri-operative course was complicated by brief use of vasopressors due to significant blood loss but patient recovered well. Surgical pathology revealed a 26 × 26 × 7.5 cm composite tumor consisting of pheochromocytoma extensively replacing the adrenal gland, with a Pheochromocytoma of the Adrenal Gland Scaled Score (PASS ) >4 suggesting aggressive potential with focus suspicious for vascular invasion. Intermixed within the same mass was EBV-positive DLBCL with extensive necrosis. Patient is currently awaiting post-op imaging and results of multi-cancer germline panel.

Conclusion: Our case highlights the diagnostic and management challenges posed by a rare combined pheochromocytoma and primary lymphoma in the same adrenal tumor. This case reinforces the need for comprehensive hormonal assessment of retroperitoneal masses to guide appropriate management.

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