CC is also known as mucinous noncystic carcinoma, a rare subtype of pancreatic ductal carcinoma, its have huge mucous protein matrix pool, mucins pool floating scattered into bundles, or a single tumor cells, signet ring cell, the WHO defines the tumor mucus ingredient at least accounted for more than 80% of the tumor entity in 2010.
CC is similar to other pancreatic tumors in clinical manifestations, usually presenting with abdominal pain, jaundice, weight loss and abdominal mass, and the median age of onset of CC is thought to be between 59 and 69 years, irrespective of gender. CA199 and CEA were elevated in tumor markers, but they were not specific. CT and MRI are important ways to diagnose CC preoperatively. CC on CT is often characterized as masses with round or lobular margins, a low attenuation masses on scan, the focal mild reinforcement on enhance,venous phase and delayed phase lesions in progressive edge and internal grid reinforcement, myxoid stroma without reinforcement, tumor boundaries clear, if not with the duodenum, it shows that the tumor is likely to have infringed the duodenum . CC on MRI performance for the edge of the outline and irregular lump,T1WI was mixed with low signal, T2WI was significantly high signal, and lesions in the low signal contrast, namely “the pepper salt”, tumor is no or mild strengthening, arterial venous phase and delayed the mid-term tumor can show progressive edge reinforcement, and the tumor grows to mesh or sponge to strengthen. In addition to imaging, fine-needle needle biopsy also plays an important role in the diagnosis of CC, and can make a clear diagnosis under the microscope after puncture sampling. However, due to the location of the pancreas in the retroperitoneum, puncture is difficult, and due to the adhesion of mucus, the process of puncture may promote the spread of the primary tumor , so it is limited in clinic.
Compared with other pancreatic cancers, CC is characterized by well-defined and large volume, mainly located in the head and neck of the pancreas, and also involving the tail of the pancreas. Most CC occurs in the context of IPMN, especially in close relation to intestinal type IPMN, as well as gastric type, pancreatic bile duct type and eosinophilic type [3, 7]. Most studies have shown that CC has a better prognosis than other pancreatic cancers, with a 5-year survival rate of 28–55% compared with 5–12% for pancreatic cancers [2, 8, 9]. Currently, the main reasons are as follows: CC and IPMN usually rich in sticky protein 2 (MUC2), and contains no sticky protein 1 ((MUC1)),but PDAC express MUC1 strongly and lack of MUC2, MUC2 epithelial cells as a barrier to inhibit invasion of tumor cells to prevent further spread, which has a tumor suppressor activity, at the same time, the CC, mismatch repair gene mutation and microsatellite instability frequency is lower, so CC and IPMN malignant degree lower[10–13], so there is even some lymph node metastasis is still alive and disease-free survival in 10 years' time . Another potential reason for the better prognosis of CC is cellular change: colloidal carcinoma cells exhibit reverse polarization,the cell base secretes mucins toward the cell-matrix interface (rather than into the lumen), thereby separating the cells from the underlying matrix. Meanwhile, lower T stage, fewer lymph node metastases,highly differentiated tumors, and fewer vascular and nerve invasion are also considered to be one of the reasons for the better prognosis of CC. However, some scholars hold different views, believing that the prognosis of CC is not good. Seidel believed that tumor site, peripheral nerve infiltration, vascular infiltration, and resection margin status were independent factors affecting the survival rate, which would then affect the prognosis.
In this case, the patients' clinical symptoms are not typical, no symptoms such as abdominal pain, jaundice, weight loss, abdominal did not touch the abnormal lump, preoperative and intraoperative diagnosis for tumor have limitations, and pancreatic tissue around the border and clear, shows that tumor in its early, prompt will have better prognosis, this is the reason why patients has no obvious symptoms. Immunohistochemistry of the patients showed positive MUC2 and CEA, similar to that reported in the literature[2–4,7−13].
At present, there is no treatment guidelines for CC, because of its rarity and morphology characterized by malignant, its treatment strategy follows the PDAC, for without distant organ metastasis and vascular invasion, have suggested that surgical resection, surgical procedure depends on the size and location of the tumor,operation methods includ pancreaticoduodenectomy, total pancreatectomy and distal pancreatectomy[4, 8, 9]. Since most CC are accompanied by IPMN, it has been proposed that if IPMN is found in the surgical margin of CC after surgery, a second operation should be performed to ensure the therapeutic effect . Radiotherapy and chemotherapy are important means for the treatment of malignant tumors, however, there is no evidence that adjuvant chemotherapy can improve the prognosis of patients [2,7−9]. Therefore, early diagnosis and treatment is an important way to improve the prognosis of CC.
In summary, pancreatic colloid carcinoma is a rare subtype of pancreatic cancer, usually associated with pancreatic intraductal papilloma. Its clinical manifestations are similar to those of other pancreatic cancers. Currently, radical surgical resection is the main treatment principle, and the prognosis is slightly better than that of pancreatic adenocarcinoma.