January 2026 Case of the Month

Submitted by Matthew Romanish, DO

Anatomic and Clinical Pathology Resident PGY-3, Department of Pathology and Laboratory Medicine, UPMC

72-year-old woman with history of immune thrombocytopenia, hypertension, remote kidney cancer s/p radical nephrectomy presents for routine CT scan for her known bilateral 3mm pulmonary nodules and a 4.2 x 3.7 cm pancreatic genu mass, suspicious for a pancreatic primary. Tumor markers: CEA: <2.0 ng/mL, LDH: 164 U/L (120-250U/L) , CA19-9: 12 U/mL (<34 U/mL). The shark core aspirates pap-stained slides showed mainly benign pancreatic ductal epithelial cells and few atypical epithelioid cells. The cell block demonstrates nests of tumor cells with clear, vacuolated cytoplasm with inconspicuous nucleoli (see figures 1 and 2). The tumor was positive for CAM 5.2, PAX-8 (see figure 3), CK7 (patchy see Figure 4), RCC (patchy see Figure 5), while negative for CK20, synaptophysin, chromogranin, and INSM1. These findings are supportive of metastatic renal cell carcinoma consistent with the patient’s prior known history.

Microscopic and Immunohistochemical Findings

Figure 1: 10x H&E

Figure 3: Pax-8 IHC

Figure 2: 20x H&E

Figure 4: RCC IHC (patchy positive)

Figure 5: CK7 IHC (patchy positive)

Final Diagnosis

Metastatic Clear cell renal cell carcinoma

Discussion

Clear cell renal cell carcinoma is the main subtype of kidney epithelial tumors, which accounts for approximately 2% of total cancers. It typically occurs in men with a peak age incidence of 60-70. Grossly these tumors have a classic golden yellow cut surface, typically arising from the renal cortex. Microscopically, the tumor cells have clear/eosinophilic granular cytoplasm with a readily apparent vascular network and grow in a solid and nested pattern. Inactivation of the VHL gene on chromosome 3p25 is a genetic hallmark of this tumor (1). PAX8 shows nuclear positivity in ~95% of cases (1). The incidence of metastatic disease to pancreas is rare (2%). The most common reported tumor origins are kidney, followed by melanoma, colorectal, breast, sarcoma and lastly lung origin. Clear cell renal cell carcinoma most commonly metastasizes hematogenously (2). The lung is the most common metastatic site, followed by bone, liver, retroperitoneum, pleura, CNS, and head and neck (2). Isolated metastatic renal cell carcinoma to the pancreas is very rare (2).

Conclusion

This case highlights an isolated metastasis to the pancreas consistent with the patient’s known history of clear cell renal cell carcinoma.

References

Nezami BG, MacLennan GT. Clear Cell Renal Cell Carcinoma: A Comprehensive Review of its Histopathology, Genetics, and Differential Diagnosis. Int J Surg Pathol. 2024 Jul 25:10668969241256111. doi: 10.1177/10668969241256111. Epub ahead of print. PMID: 39051572.
Sellner F, Thalhammer S, Klimpfinger M. Isolated Pancreatic Metastases of Renal Cell Cancer: Genetics and Epigenetics of an Unusual Tumour Entity. Cancers (Basel). 2022 Mar 17;14(6):1539. doi: 10.3390/cancers14061539. PMID: 35326690; PMCID: PMC8945920.