Solid Tumor Metastases to the Pancreas Diagnosed Using Fine-Needle Aspiration

OBJECTIVES

Solid tumor metastases to the pancreas are rare, and only limited literature on the topic is available. In this retrospective study, we reviewed 107 cases of solid tumor metastases to the pancreas diagnosed by fine-needle aspiration (FNA) from 2005 to 2019.

METHODS

Information including the patients' clinical histories, radiologic and pathologic findings, treatments, and follow-up were collected.

RESULTS

The mean age of the patients was 62.4 years. The mean tumor size was 2.64 cm with even distribution throughout the pancreas (head, neck and body, and tail). The most common primary site was the kidney, followed by the lung, skin, and breast and the gynecologic, gastrointestinal, and genitourinary tracts. The most common tumor type was carcinoma, followed by melanoma and sarcoma. In comparison to patients with nonkidney primary cancers, those with primary renal cell carcinoma had a longer median interval between primary diagnosis and metastasis (8.5 vs 4.0 years; P < .01), less often had metastasis outside the pancreas (38% vs 74%; P < .01), and had a significantly longer 5-year survival rate (65.7% vs 24.8%; P < .01).

CONCLUSIONS

FNA plays a crucial role in diagnosing metastases to the pancreas. Metastases originating from kidney and nonkidney primary tumors have distinct clinicopathologic features and prognoses.

Pancreatic metastasis of Merkel-cell carcinoma: a rare neoplasm of the pancreas

Only 2-3.9% of pancreatic malignancies represent metastases from other sites, the most common origins being the lungs, kidneys, and gastrointestinal tract. Differentiating between primary and secondary lesions may be challenging with imaging techniques but EUS-guided FNA is a safe, accurate procedure for obtaining a tissue diagnosis. We report the case of a 70-year-old male who, following satisfactory treatment for a Merkel-cell carcinoma in the right groin, presented with jaundice and an indurated, vascularized, adherent nodule on the right thigh. Endoscopic ultrasound identified a mass at the pancreatic head as well as a perilesional adenopathy with no evidence of vascular involvement. FNA revealed cell proliferation, which was immunohistochemically positive for CD56, synaptophysin, and chromogranin, these findings being consistent with poorly-differentiated neuroendocrine carcinoma. Given the patient's history we considered this lesion to be a pancreatic metastasis of Merkel-cell carcinoma, which represents a rare finding.

Differential diagnosis of solid pancreatic masses

Solid pancreatic lesions include mainly adenocarcinoma, neuroendocrine tumors pancreatic cystic neoplasms with solid component, solid pseudopapillary tumor, pancreatoblastoma, pancreatic lymphoma, and pancreatic metastasis. The most frequent pancreatic lesion is the adenocarcinoma, representing between 70% and 95% of all solid pancreatic neoplasm. The diagnosis of these lesions can be a challenge and currently, there are different imaging techniques such as CT scan, EUS and MRI with high sensitivity and specificity. The most widely used technique for the initial evaluation is the CT scan with a sensitivity between 76% and 92% for the diagnosis of pancreatic cancer. The EUS has a sensitivity for the detection of pancreatic lesions of around 98% and is accepted to be the most sensitive technique for the detection of small pancreatic tumors (<2 cm). The MRI, with a very high soft-tissue contrast resolution, provides an accuracy in the detection and staging of adenocarcinoma of 90-100%. A multimodality approach is usually necessary in patients with clinical suspicion of pancreatic lesion. The EUS is required for the local evaluation of the relation of the lesion with vessels and for tissue acquisition and the CT scan and/or MRI is usually required for the local and distance staging in case of pancreatic cancer. The purpose of this review is to provide an overview of solid pancreatic lesions and the role of the different imaging techniques in their evaluation.