Primary pancreatic lymphomas: a cytopathologic analysis of a rare malignancy

BACKGROUND: Primary pancreatic lymphomas (PPL) are extremely rare. Clinically, PPL usually present with symptoms of carcinoma of the pancreatic head. An accurate cytopathologic diagnosis by fine-needle aspiration (FNA) is imperative because the primary treatment is nonsurgical, based on a combination of chemotherapy and radiation therapy. METHODS: Eight cases of PPL were identified from the pathology files of The Johns Hopkins Hospital over a 14-year period (1989-2003). All cases were diagnosed on FNA performed under radiologic guidance. Needle rinses were used to perform flow cytometric (FC) analysis. No tissue studies were performed after the FNA diagnosis was made. RESULTS: A strong male predominance (male-to-female ratio of 7:1) was noted. The patients ranged in age from 35-75 years (mean age, 55 years). The tumors varied in size from 2-14 cm, as evaluated on the radiologic scans (mean dimension of 8.0 cm). Abdominal pain was the most common presenting symptom (six patients) followed by jaundice, acute pancreatitis, small bowel obstruction, and diarrhea. The cytomorphologic features included hypercellularity with discohesive cells with round nuclei, often prominent nucleoli, mitoses, and karyorrhexis. By FC analysis, all eight cases demonstrated a monoclonal pattern of immunoglobulin light chain expression. The patients were treated with either chemotherapy alone or in conjunction with radiation therapy or stem cell transplantation. CONCLUSIONS: PPL is an extremely rare pathologic entity. FNA coupled with FC analysis appears to be highly accurate in the diagnosis of PPL and is the sole diagnostic modality used clinically. Based on cytomorphology, the main differential diagnoses of PPL involve secondary lymphoma, pancreatic endocrine neoplasm, and florid chronic pancreatitis. An accurate FNA diagnosis of PPL is critical for timely, nonsurgical management and obviates the need for an exploratory laparotomy.