DISCUSSION
Diagnosis of SPN of the pancreas is crucial because its prognosis is completely different from most pancreatic tumors with favorable long term outcomes [15]. In this case, a surgical specimen was needed before a definitive diagnosis of SPN could be made. This might be explained by the lack of pathognomonic clinical presentation with vague and mild symptoms in the beginning, without alarm features, mostly interpreted as functional dyspepsia, which might have delayed the diagnosis. Moreover, SPN are mostly found in female patients under 35 years, in a 29 case series under 20 years of age [2], and this patient was older. In fact, less than 10% of SPN cases have been reported in patients older than 40 years of age [16].
Also, in this case, EUS finding were not specific enough to define the diagnosis of SPN and NET with cystic degeneration was suspected. Pancreatic NET and SPN are frequently a diagnostic challenge [17] and definitive preoperative diagnoses are made in only a minority of cases of SPN [18]. In a large study that included 718 patients, only 52 patients (7%) received a confirmed preoperative diagnosis of SPN based on the findings of FNA [19]. Contrast enhanced EUS could be used to visualize the blood flow inside the tumor, however, in this case, the SPNs was hypovascular compared with the surrounding pancreatic parenchyma. Also, sparsely cellular smears with limited amount of cytological material obtained from fine-needle biopsies pose significant diagnostic challenges since the typical pseudopapillary structures are absent. Due to the partial overlap in immunohistochemistry in SPN and neuroendocrine neoplasm, a diagnosis of a neuroendocrine tumor is a potential pitfall in cytology smears with only isolated cells.
In this case, due to the large cystic component of the lesion, a FNA needle was chosen over a FNB needle. Probably, if a FNB was performed, a larger sample could have allowed a definite diagnosis. Song et alproposes some FNA cytomorphologic features that can help define the diagnosis, namely the presence of marked cellularity with pseudopapillary fragments composed of fibrovascular cores lined with one to several layers of tumor cells intermingled with discohesive neoplastic cells and inter- or intra-cellular pink hyaline globules, mucus-like globules surrounded by the stromal cells and cellular debris [20].
Surgical resection is often not difficult because is an encapsulated tumor and prognosis is excellent [2]. However, there are risk of metastasis (most commonly to the liver), or tumor recurrence, which is associated to large tumor size (more than 5 cm), lymphovascular invasion, metastasis to the regional lymph nodes, synchronous metastatic disease and positive resection margins [21]. Furthermore, close follow up of the patients after surgical resection is advised for early diagnosis of local recurrence and metastatic disease [18]. In our case, the patient is asymptomatic with no signs of metastatic disease or recurrence in the 6 months’ post-operative follow up.