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.