5-Discussion
Pancreatic metastasis is rare, accounting for only 2% of all pancreatic cancer8. The primary tumors that metastasize frequently to the pancreas are lung cancer, renal cell carcinoma, breast cancer, melanoma and colon cancer9.
Ewing sarcoma is a rare bone tumor and depending on whether metastases were present at diagnosis, patients with ESFT have considerably different five-year overall survival rates (OS) ranging from 70% if localized to 9–41% for metastatic disease10.
Hyma et.al reviewed a 39 cases of ESFT involving the pancreas, with only four of them being metastatic lesions11. The 4 cases were younger than 30 years of age, with two of them testing positive for CD 99 and one testing positive for PAS in terms of pathologic features. There is also a male predominance with only one female case.
A review done by Saif et.al showed no gender predilection in Ewing sarcoma /primitive neuroectodermal tumour (ES/PNET) with the majority diagnosed at their teenage years with disseminated disease at the diagnoses12.
The diagnosis of pancreatic metastases can be made safely and effectively with endoscopic ultrasonography (EUS) and confirming the diagnosis using immunohistochemistry9. Out of the 39 cases described in the literature, CD99 is the most frequently reported marker linked to ES. Other related markers that are less precise are synaptophysin, vimentin, and neuron-specific antigen11.
Radiation, chemotherapy, and surgical resection were used to treat these individuals; however, the prognosis was poor with two resulting deaths from the disease. Similarly, our case was a young male patient with positive CD 99 in terms of pathologic features.
The prognosis for ESFTs has significantly improved after multiagent chemotherapy was added to surgery and/or radiation treatment. Children with localized illness who get combined-modality treatment have a 65% to 70% progression-free survival rate (PFS)13. The EURO-EWING 99 trial demonstrated that patients who received local treatment for both the primary and metastatic disease had a three-year event-free survival rate that was significantly higher compared to patients who only received local treatment for the primary or metastatic disease14.
Another differential diagnosis in young patients is small cell neuroendocrine carcinoma due to the similarity in morphological characteristics, imaging and immunohistochemistry which can delay the proper therapy. Hence, to confirm the diagnosis, molecular study should be employed.
In conclusion, we present a rare case of ES metastasis to the pancreas in a 38-year-old male with prior diagnosis and treatment of ES of the left foot unresponsive to chemotherapy. Our case emphasizes the rarity of pancreatic ES metastases, since only four previous cases have been documented in the literature. Pancreatic metastasis can be diagnosed with immunohistochemistry stain, with CD99 being the most frequently found marker linked to ES.
Figure 1 legend: Well circumscribed mass measuring 14 mm at the junction of the body and tail of the pancreas (white arrow).
Figure 2 legend: Figure 2a :13 mm cyctic lesion obstructing the Wirsung duct, which is dilated upstream.
Figure 2b: FNA needle 22G inside the lesion.
Figure 3 legend: Figure 3a: Small round blue cell in H&E stain.