The most common indications for pancreatic resection are ductal adenocarcinoma, a neuroendocrine tumor or chronic pancreatitis. The three cases we have described are rare. We would like to present an overview of these unusual conditions:
Benign multicystic mesothelioma was first described by Mennemeyer and Smith in 1979 . It is a very rare tumor originating from the peritoneum but it can also be found on serosal surfaces (for example, intestine, liver and kidney). To our knowledge, this is the first description in the literature of benign multicystic mesothelioma of the pancreas.
Although it is a tumor with a benign clinical behaviour, it frequently recurs after surgical resection. A report of 15 cases revealed a recurrence rate of 26.7% [5, 6]. Time between recurrences may range from four months to 12 years . As it has a tendency to recur, a neoplastic etiology is supported. In our patient, 10 months postoperatively there had been no evidence of recurrence.
Benign multicystic mesothelioma is found mainly in women of reproductive age with a past history of abdominal surgery or endometriosis . Only a few reports exist of this gynecologic diagnosis in elderly women . Our patient had not undergone any previous abdominal surgery.
The clinical findings of benign multicystic mesotheliomas are non-specific and include nausea, vomiting and abdominal pain. There is often a palpable abdominal mass, although this was not present in our case . Preoperative diagnosis is often difficult and several differential diagnoses must be considered. As this tumor has a high risk of recurrence, a close follow-up should be performed in every patient.
Adenomyomas are common in the stomach, gallbladder and jejunum but are very unusual in the common bile duct or the ampullary region . Adenomyomas of the extrahepatic bile duct are defined as non-neoplastic, tumor-like localized lesions characterized by glandular and myomatous hyperplasia without cellular atypia . In the absence of gallstones, extrahepatic bile duct adenomyomas often stay dormant for long periods and may eventually cause vague symptoms due to local pressure . They also cause obstructive jaundice, as in this case, which can easily be misinterpreted as a malignant neoplasm. It is difficult to differentiate between biliary adenomyomas and other malignant lesions by radiology (CT). Since malignancy is often suspected preoperatively, surgery with the intent to cure should be performed.
The etiology of adenomyomas of the extrahepatic bile duct and the ampulla of Vater is unknown. As different terms are used in the literature to describe the same histological lesion, the true incidence of adenomyomas of the ampullary region is unclear. In the literature, 30 cases of adenomyomas of the ampulla of Vater and 13 cases of the extrahepatic bile duct have been reported [11, 13]. Adenomyomas are usually diagnosed by histopathologic examination after surgery. As in our case, it often turns out to be a surprising diagnosis.
Undifferentiated carcinoma, sarcomatoid variant, is a rare variant of pancreatic tumors. The malignant tumor arises de novo or occurs in association with mucinous cysts or other pancreatic neoplasms. Men are affected more often than women with a ratio of 3:1 and a mean age at diagnosis of 63 years. The most common symptoms are fatigue, nausea and vomiting, weight loss and abdominal pain. As in our case, radiologic imaging often shows an aggressive pancreatic mass which is not specific for undifferentiated carcinoma. Undifferentiated carcinomas are usually very large, aggressive neoplasms (average size 9-10 cm size). The prognosis is often limited to several months after resection . Our patient remains in good physical condition seven months postoperatively, although he did develop two new liver metastases under chemotherapy which were resected. In contrast to our case, metastases are usually present at the time of diagnosis, the most common sites being lymph nodes, liver and lung. Surgical resection is the treatment of choice, although most of these neoplasms have already metastasized in the majority of patients by the time of diagnosis . Histologically, the neoplasm may resemble a sarcoma due to the spindle cells. In contrast to a carcinomasarcoma, which consists of a mixture of glandular and spindle cell differentiation, an undifferentiated carcinoma, sarcomatoid variant, has only a prominent spindle cell differentiation. Cytokeratin is expressed in over 80%. Sarcomatoid carcinomas can be differentiated from carcinosarcomas which immunohistochemically show cytokeratin and vimentin reactivity and are, therefore, not considered to be true carcinomas . The spindle cells of sarcomatoid carcinomas often label for actin, although desmin is not frequently expressed. In our case desmin was expressed and actin was negative.