Fig.1 
Fig. 2 
Fig.3 
Fig. 4
A 51-year-old woman presented with a 6 moths history of fatigue,
myalgia and intermittent diarrhea. A colonoscopy was negative.
There were no evidence of an infection or parasitic infestation.
The diarrhea was partly responsive to a lactose-free diet. On
further investigations, an abdominal ultrasound revealed a lobular
mass in the body and tail of pancreas measuring 4.8 x 4.8 x 3.8
cm. The tumor was excised. Six weeks post-operatively, the patient
reported a marked reduction in symptoms.
The tumor was well-vascularized and consisted of solid sheets of cells [FIG 1]. Focal degenerative changes were present in many areas and were associated with cytoplasmic swelling, accumulation of foamy macrophages and cholesterol clefts. In these regions, there were numerous intra- and extracellular PAS-positive granules [FIG 2]. There areas merged with papillary formations [FIG 3]. However, in either solid and papillary areas, tumor cells were homogeneous in appearance; polygonal cells with centrally located nuclei with a loose chromatin structure and inconspicuous nucleoli were present throughout. The cytoplasm was slightly eosinophilic [FIG 4].
To access light micrographs, use Figure 1.
Fig.1 Fig. 2
Fig.3 Fig. 4
In the best preserved areas, the tumor cells were polygonal and contain central nuclei with small indentations and inconspicuous nucleoli. The cytoplasm contained abundant number of mitochondria [FIG 5]. Annulate lamellae were seen in many cells. There were no neurosecretory granules. The cells were joined by occasional rudimentary cell junctions. There was no glandular differentiation, and only very rare microvilli were seen in some intercellular spaces [FIG 6]. In degenerate areas, in addition to the findings described above, numerous lysosomes were present in the cytoplasm [FIG 7].
Fig.5
Fig. 6 
Fig. 7Solid and papillary epithelial neoplasm of pancreas
Based on the light microscopy findings, the differential diagnosis is vast and includes islet cell tumor of pancreas, cystadenoma/carcinoma, pancreatoblastoma and acinar cell carcinoma. The clues leading to the correct diagnosis in this case is the growth pattern that includes the solid areas and papillary transformation in areas showing degenerative changes. Ultrastructurally, the absence of differentiation in otherwise relatively innocuous-looking cells is almost specific for that diagnosis. More importantly, electron microscopy confirms the absence of neurosecretory differentiation. Differentiation towards other known cell types in the pancreas is usually absent, although a ductal origin has been hypothesized by some [1]. Indeed, the centroacinar cell bears the most analogy with cells composing the solid and epithelial neoplasm of pancreas.
Solid and papillary tumors of the pancreas are tumors of uncertain histogenesis which account for up to 2 to 3% of all pancreatic neoplasms [2]. These relatively rare tumors have a predilection for young non-Caucasian women. Most patients are asymptomatic or complain of vague abdominal symptoms. Thus, in the appropriate clinical setting, the possibility of a solid and papillary epithelial neoplasm of pancreas should always be considered in the differential diagnosis. In this particular case, it was the ultrastructural features that were instrumental in arriving at the correct diagnosis. In general, these tumors have an excellent prognosis following surgical intervention, and although malignant behavior is observed in up to 14.7% of case, mortality is low [3].
![[----------------------------]](../../Images/bl_bar.gif)
