Desmoid tumor is a rare form of neoplasm. It is clonal fibroblastic proliferation that arises in the deep soft tissues and can be classified into extra-abdominal, abdominal, and intra-abdominal DT. It can also be divided into sporadic or familial adenomatous polyposis (FAP)-associated DT. FAP-associated DT is called Gardner syndrome (GS). Intra-abdominal DT of the GS type is rarer, with an incidence rate of approximately one per million. The sporadic intra-abdominal DT is even rarer. A review of the English-language literature found no more than 100 cases reported5. Only in 15 of these, the DT was found in pancreas (Table 1)[5–20].
The symptoms of DT are not typical. Rather, they depend on the location of the tumor. The 15 known cases of pancreatic DT presented symptoms that consisted primarily of abdominal discomfort, epigastric pain (10/15), and weight loss (4/15). One patient was asymptomatic, and one involved chest pain. None of the cases exhibited painless jaundice, the main symptom of pancreatic head cancer. It is unusual to see a patient with pancreatic head DT, as it normally does not obstruct the common bile duct. However, our patient had elevated levels of bilirubin and the serum tumor marker CA19-9. To the best of our knowledge, the case described here is the first DT with symptoms of jaundice and higher CA19-9 to be reported.
Of the previously reported cases, two went through two surgeries. The case reported by Bruce et al. developed DT following distal pancreatic resection. The other case was found after resection of a neuroendocrine tumor. The first operation preserved about 6 cm of the pancreas while removing the pancreatic tail, and the DT was located on the remnant pancreatic body. The etiology of the intra-abdominal DT has not been well defined. A history of trauma or surgery at the site of the tumor might be one of the reasons, as in our case. The patient was injured four weeks earlier when falling from his bicycle and hurting the upper abdominal area. It took about a month, so, in our opinion, the injury might have been the cause. Among the reported cases, this is the first time for an injury to be described as the cause of pancreatic DT.
The diagnosis of pancreatic DT before surgery is challenging. The first tentative diagnosis was pancreatic cancer, as the patient had jaundice, elevated CA 19 − 9, and a solid tumor located in the neck of the pancreas. Pancreatic cancer, however, was incompatible with the patient’s age. With a history of injury, we believed that acute pancreatitis could also explain the symptoms. However, the patient had no symptoms specific to pancreatitis, and the blood and urine amylase levels were normal. Moreover, it is histologically challenging to distinguish pancreatic DT from other uncommon pancreatic tumors such as gastrointestinal stromal tumor (GIST), neuroendocrine tumor, lipoma, and carcinoid tumor. For this reason, it is useful to perform immunohistochemical staining to confirm the diagnosis of pancreatic DT. Staining for β-catenin is especially useful, as both sporadic fibromatosis and fibromatosis associated with GS demonstrate adenomatous polyposis coli (APC) gene mutation. This mutation leads to the accumulation of β-catenin in the cytosol and nucleus. Thus, special staining for β-catenin can exclude neural cells or GIST, which express CD117 and CD34 markers. Therefore, the diagnosis of pancreatic DT can be established based on the histological and immunohistochemical findings.
Until now, the mainstay treatment of for pancreatic DT is complete resection, in part because of the tumor’s ability to invade surrounding structures. In our case, surgery was the optimal strategy for the patient. We performed a PPPD because of the diagnosis of pancreatic adenocarcinoma. Sometimes, performing resection with a free margin is difficult because of the scope of invasion. So, for high surgical risk cases, chemotherapy or radiotherapy should also be considered. Wang and Wong reported a case of a 57-year-old woman, who presented with a 10-cm mass on the pancreatic head. They performed partial cystectomy, followed by treatment with celecoxib, a non-steroidal anti-inflammatory drug (NSAID), for six months. By that time, the cyst lesion had completely disappeared.Whether such an approach should be followed requires the support of a large controlled experiment. Surgical resection, if possible, is the preferable choice for these rare tumors.
In the report by Bruce and colleagues, it was noted that DT recurrence rate seems to differ greatly between sporadic and familial cases. The rate of recurrence among sporadic DT is low.Within the 15 reported cases, the tumor recurred in only one case, and in that case, the tumor was associated with FAP. The prognosis of pancreatic DT is unknown. Recurrence has not been observed during the follow-up period after the curative resection in our case. Similarly, most reported cases of pancreatic DT had a favorable survival outcome. Our patient was observed for 48 months postoperatively and remained free of the disease.
In summary, sporadic pancreatic DT is a rare tissue tumor, which has the potential to be invasive. Pancreatic DT is challenging to diagnose and often tends to be misdiagnosed. In our case, we initially misdiagnosed it because of the obstructive jaundice and the high level of CA19-9. However, immunohistochemistry diagnosed it as pancreatic DT since it was possible to differentiate between it and other soft tissue tumors. Trauma may be the etiology of the DT in our case. Radical resection is recommended as the first line of treatment for DT. Based on the reported cases we have reviewed, the prognosis for pancreatic DT is good. Adjuvant therapy is not required, but treatment with NSAIDs might be effective for unresectable neoplasm.