Contributed by Eizaburo Sasatomi, MD, PhD and Alyssa M Krasinskas, MD.
Published on line in February 2004
A male inhis 40s presented to the emergency department with abdominal pain, nausea and vomiting. A computed tomography (CT) scan showed an 8 cm mass in the tail of the pancreas (Fig. 1). He underwent distal pancreatectomy and splenectomy.
A tumor measuring 11 x 10 x 4.5 cm was present within the tail of the pancreas and it was focally adherent to the spleen. The external surface of the tumor was smooth and focally bosselated. Cut sections showed an encapsulated, fleshy gray-brown tumor with a soft and friable consistency. There were scattered areas of necrosis and hemorrhage. The lesion was well-demarcated from the adjacent pancreas tissue.
The tumor was thickly encapsulated except for areas within the pancreas where the tumor had a pushing border as it invaded into the adjacent pancreas (Fig. 2). The tumor was divided into lobules by predominantly thin fibrous septa. These lobules were comprised of a monotonous population of cells arranged in solid sheets with a delicate fibrovascular network (Fig. 3). Focally at the edges of the tumor, trabecular-type structures and rosette formations were seen (Fig. 4). Areas of geographic coagulative-type necrosis were present only focally within the tumor. The tumor cells had high nuclear-to-cytoplasmic ratios and the nuclei had an open chromatin pattern with prominent nucleoli (Fig. 5). The cytoplasm was predominantly eosinophilic and occasionally amphophilic. Up to 5 mitotic figures were seen per 10 high power fields. A focus suspicious for vascular invasion was present. The tumor was also present within the hilum of the spleen, but it did not invade the splenic capsule.
HISTOCHEMICAL AND IMMUNOHISTOCHEMICAL STAININGS:
PAS and PAS-D stains showed focal weak positive granularity within rare tumor cells (Fig. 6). Immunohistochemically, the tumor cells were positive for cytokeratin CAM 5.2 (Fig. 7) and synaptophysin (Fig. 8). Scattered cells were weakly positive for chromogranin (Fig. 9). Immunohistochemical stains for Insulin, glucagon, gastrin, somatostatin and CD56 were all negative.
ELECTRON MICROSCOPIC FINDINGS:
Low power views highlighted cells that formed vague acinar-type structures with a central lumen (Fig. 10). There appeared to be microvilli at the luminal surface. The nuclei were basally oriented and the cytoplasm contained abundant zymogen granules located toward the apical surface (Fig. 10). The cytoplasm also contained abundant rough endoplasmic reticulum. Several cells showed fibrillary structures within the cytoplasm (Fig. 11). No electron dense endocrine granules were identified.
ADDITIONAL INFORMATION AND SPECIAL STUDIES:
Based on these preliminary findings, the clinician tested the patient's serum lipase level, which came back as 822 IU/L (normal range 23-300 IU/L). Slides were also sent out for a trypsin immunohistochemical stain (Fig. 12).