Intraductal papillary mucinous tumors of the pancreas

Cystic neoplasms of the exocrine pancreas are a small fraction of pancreatic tumors. Within that group of cystic neoplasms, intraductal papillary mucinous tumors (IPMTs) can be distinguished from mucinous cystic neoplasms, serous cystic neoplasms, and pseudopapillary cystic tumors. Awareness of IPMTs has increased since the World Health Organization classified these tumors as its own group in 1996. Because of their favorable prognosis, an extensive diagnostic workup for IPMTs should be performed in patients presenting with cystic lesions of the pancreas. This workup often leads to the diagnosis and the predominant tumor location and size, although the extent of the ductal changes can only be established by histopathology. Surgical resection is the therapy of choice for IPMTs. The type of resection depends upon the extent of the quantitative and qualitative ductal involvement. Total pancreatectomy is currently the treatment for an IPMT that comprises the entire main duct.     

Immunohistochemical analysis of molecular biological factors in intraductal papillary-mucinous tumors and mucinous cystic tumors of the pancreas

BACKGROUND: To investigate the malignancy and differentiation of intraductal papillary-mucinous tumors (IPMTs) and mucinous cystic tumors (MCTs) of the pancreas, clinicopathologic characteristics and immunohistochemical features were analyzed. METHODS: The clinicopathologic characteristics and immunohistochemical features of 24 patients with IPMT and 8 with MCT who underwent pancreatic resections at our hospital were examined. Immunohistochemical features analyzed included expression of p53 protein, proliferating cell nuclear antigen, integrins, interleukin-1 receptor type I, and hormone-associated receptors, and the factors correlated with malignancy were identified by multiple logistic regression. RESULTS: Among the IPMTs, there were 16 intraductal papillary adenomas, 5 intraductal papillary adenocarcinomas, and 3 moderate dysplasias. Among the MCTs, there were 6 mucinous cyst adenomas and 2 mucinous cyst adenocarcinomas. Multivariate analysis revealed that of the clinicopathologic characteristics, only the presence of mural nodules (odds ratio (OR) 7.12, P = 0.044) was independently correlated with the malignancy of IPMTs, and that of the immunohistochemical features, only alpha integrin subunit expression was independently correlated with malignancy of pancreatic mucinous tumors (OR 15.6, P = 0.036), especially IPMTs (OR 35.7, P = 0.012). CONCLUSION: These results indicate that alpha-containing integrin expression can be a significant marker of malignancy in pancreatic mucinous tumors.     

Endoscopic diagnosis and staging of mucinous cystic neoplasms and intraductal papillary-mucinous tumors

Background/Purpose. The number of patients with cystic neoplasms of the pancreas as detected using various types of imaging techniques has been steadily increasing. Among the cystic neoplasms, mucinous cystic neoplasms (MCNs) and intraductal papillary-mucinous tumors (IPMTs) were comparatively more frequently encountered. We used imaging techniques to focus on the differential diagnosis of MCNs and IPMTs, and tumor staging.Methods. Fifteen patients with MCNs with ovarian-like stroma and 109 patients with IPMTs were experienced. We examined the image findings for the differential diagnosis and stage diagnosis of these two types of cystic neoplasms.Results. Endoscopic ultrasonography could reveal detailed images of internal structure and was effective for the diagnosis of MCNs. Other endoscopic imaging modalities could not give specific findings for MCNs. Endoscopic retrograde cholangiopancreatography (ERCP; including duodenoscopic findings and pancreatogram) and pancreatoscopy showed the characteristic and specific findings of IPMTs. Also, endoscopic ultrasonography and intraductal ultrasonography were found to have high sensitivity and diagnostic accuracy for their differential diagnosis of neoplastic/nonneoplastic and invasive/noninvasive lesions in IPMTs.Conclusions. Endoscopic imaging techniques are capable of revealing the detailed structure of pancreatic cystic lesions. They are effective for differential diagnosis, for assessing the degree of malignancy, and for deciding upon an appropriate treatment in patients with IPMTs.     

Clinicopathologic study of intraductal papillary-mucinous tumors and mucinous cystic tumors of the pancreas

BACKGROUND/AIMS: We analyzed clinicopathologic and imaging findings of intraductal papillary-mucinous tumors (IPMTs) and mucinous cystic tumors (MCTs) of the pancreas to evaluate the difference between IPMTs and MCTs, and to identify the signs indicative of malignancy in IPMTs. METHODOLOGY: Clinicopathological features of 20 patients with IPMT and six patients with MCT of the pancreas were studied. RESULTS: The patients with IPMT comprised 16 males and four females with a mean age of 62.9 years. Eighty percent of IPMTs were located in the pancreatic head, and the mean tumor size was 38.6mm. Recurrence was observed in one patient, who died of IPM adenocarcinoma. In contrast, all patients with MCT were females, with a mean age of 53.0 years. None of the MCTs arose in the pancreatic head, and the mean tumor size was 42.7mm. One patient died of MC adenocarcinoma, but all of the others survived without recurrence. The difference in gender, location of the tumor, and connection to the pancreatic duct reached statistical significance between IPMTs and MCTs. A significant connection to the pancreatic duct and high level of serum carbohydrate antigen 19-9 (CA19-9) was observed in the adenocarcinoma and moderate dysplasia groups of IPMT. CONCLUSIONS: The main duct type and an elevation of serum CA19-9 level suggested malignancy in IPMTs.     

Immunohistochemical analysis of molecular biological factors in intraductal papillary-mucinous tumors and mucinous cystic tumors of the pancreas

Background: To investigate the malignancy and differentiation of intraductal papillary-mucinous tumors (IPMTs) and mucinous cystic tumors (MCTs) of the pancreas, clinicopathologic characteristics and immunohistochemical features were analyzed. Methods: The clinicopathologic characteristics and immunohistochemical features of 24 patients with IPMT and 8 with MCT who underwent pancreatic resections at our hospital were examined. Immunohistochemical features analyzed included expression of p53 protein, proliferating cell nuclear antigen, integrins, interleukin-1 receptor type I, and hormone-associated receptors, and the factors correlated with malignancy were identified by multiple logistic regression. Results: Among the IPMTs, there were 16 intraductal papillary adenomas, 5 intraductal papillary adenocarcinomas, and 3 moderate dysplasias. Among the MCTs, there were 6 mucinous cyst adenomas and 2 mucinous cyst adenocarcinomas. Multivariate analysis revealed that of the clinicopathologic characteristics, only the presence of mural nodules (odds ratio (OR) 7.12, P?=?0.044) was independently correlated with the malignancy of IPMTs, and that of the immunohistochemical features, only α[Formula: See Text] integrin subunit expression was independently correlated with malignancy of pancreatic mucinous tumors (OR 15.6, P?=?0.036), especially IPMTs (OR 35.7, P?=?0.012). Conclusion: These results indicate that α[Formula: See Text]-containing integrin expression can be a significant marker of malignancy in pancreatic mucinous tumors.     

Intraductal papillary-mucinous tumor of the pancreas: a historical review of the nomenclature and recent controversy.

A number of studies on mucin-producing cystic neoplasm of the pancreas have been reported since the first report of the tumor in 1982. There has been some controversy about nomenclatures and clinicopathologic entities of mucin-producing cystic tumor, mucinous cystic tumor, and intraductal papillary tumor of the pancreas. In 1996 and 1997, new classifications of pancreatic neoplasms were published by the World Health Organization (WHO) and Armed Forces Institute of Pathology (AFIP). According to the new WHO and AFIP classifications, mucin-producing cystic neoplasm of the pancreas corresponds mainly to intraductal papillary-mucinous tumor and mucinous cystic tumor of the pancreas. and these two diseases are independent conditions. Intraductal papillary-mucinous tumor is regarded as a unique clinical entity, but controversy remains about the term and clinicopathologic entity. Some confusion and problems remain betweeen the two lesions. In this review, we review their historical background, terminology, WHO and AFIP classification, and problems with classification.     

Intraductal papillary-mucinous tumor and mucinous cystic neoplasm: CT and MR findings

Summary Cystic lesions of the pancreas are increasingly detected by imaging at daily clinical practice. Among them mucinous cystic tumor and intradcutal papillary-mucinous tumor of the pancreas are clinically important since they are latently or overtly malignant and still have potentially good prognosis after resection. In this review article we describe history, clinicopathology and differential diagnosis of two entities, and findings and role of CT and MR imaging as well as MR cholangiopancreatography in the diagnosis and evaluation of intraductal papillary-mucinous tumor.     

IHPBA in Tokyo, 2002: surgical treatment of IPMT vs MCT: a Japanese experience

The differences and similarities between intraductal papillary mucinous tumor (IPMT) and mucinous cystadenoma or carcinoma (mucinous cystic tumor; MCT) of the pancreas have been noted. The similarities include: (1) both tumors originate from pancreatic duct cells, (2) massive mucin production is found in both tumors, and (3) papillary projection is a common histological characteristic. However, there are also many differences. IPMT is most frequently found in men in their sixties, and originates in the head of the pancreas, with 62% (123/199) of tumors reported to be found in the head of the pancreas. This tumor sometimes spreads throughout the entire pancreas. The tumor itself basically is of the dilated pancreatic duct type, and the prognosis is generally good. In contrast, MCT frequently develops in women in their forties. This tumor is usually large, round, and almost totally encapsulated by fibrous tissue, with no communication with the pancreatic duct. The tumor histologically has an ovarian-like stroma. It most often develops in the body or tail of the pancreas. Invasion is often present and the operative prognosis is not good. IPMT resembles the shape of a bunch of grapes and MCT resembles that of an orange. From the differences between these two types of tumors, they are classified into different categories. With regard to therapeutic strategies for MCT, the tumor should be resected with lymph node dissection immediately when it is detected. In contrast, some patients with branch-type IPMT can be followed without surgical procedures. Because IPMT shows good prognosis and little tendency for infiltration, some kinds of organ-preserving procedures would be possible for some patients with this tumor. Such organ-preserving procedures are: duodenum-preserving pancreas head resection, spleen-preserving distal pancreatectomy with conservation of the splenic artery and vein, and so on.     

Endoscopic ultrasound characteristics of mucinous cystic neoplasms of the pancreas

OBJECTIVE: Mucinous cystic neoplasms of the pancreas have a more favorable prognosis than ductal adenocarcinoma. Management of a subgroup, intraductal papillary-mucinous neoplasms, is controversial. Endoscopic ultrasound (EUS) with fine-needle aspiration biopsy may emerge as the imaging modality of choice. There are few studies describing the EUS features of these tumors. METHODS: A total of 35 consecutive cases of cystic tumors of the pancreas with an established pathological diagnosis were analyzed for characteristic EUS features. RESULTS: Mucinous cystadenocarcinomas (n = 14) were more likely to be characterized by hypoechoic cystic/solid mass or complex cyst and were frequently associated with a dilated main pancreatic duct. Benign mucinous duct ectasia (n = 6) were characterized by a dilated main pancreatic duct in conjunction with hyperechoic thickening of the duct wall. The two cases of intraductal mucinous hyperplasia additionally showed a hypoechoic mass. Intraductal papillary carcinoma (n = 11) had features in common with mucinous cystadenocarcinoma but also had echogenic foci in the mass and intraductal hyperechoic lesions. The two cases of microcystic cystadenoma showed either a mixed hypoechoic solid/cystic mass or a complex cyst without the additional features seen in mucinous cystadenocarcinoma. CONCLUSIONS: EUS features seem to exist that may help to differentiate cystic neoplasms from adenocarcinoma of the pancreas and, thus, to establish the preoperative diagnosis of cystic tumors of the pancreas.     

MUC1 overexpression is the most reliable marker of invasive carcinoma in intraductal papillary-mucinous tumor (IPMT)

BACKGROUND/AIMS: To clarify the development of pancreatic cancer we performed immunohistochemical analysis of the presence of the major apomucin and cell-cycle regulatory proteins using the tissues of IPMT and ductal adenocarcinoma (DC) of the pancreas. METHODOLOGY: Formalin-fixed and paraffin-embedded tissues of 24 IPMT and 21 DC cases were subjected to immunohistochemical staining for MUC1, MUC2, p16, p53 and DPC4. According to the WHO classification, there were 10 intraductal papillary-mucinous adenomas (IPMA); 3 borderline intraductal papillary-mucinous neoplasms (IPMB); 4 intraductal papillary-mucinous carcinomas (IPMC), non-invasive type (nIPMC); 4 IPMCs with invasive muci nous carcinoma (IPMC/muc); and 3 IPMCs with invasive tubular adenocarcinoma (IPMC/tub). RESULTS: MUC1 expression was seen in 6 of 7 invasive IPMCs (86%) and in all DCs (100%). MUC2 was only seen in non-invasive IPMT and in a part of IPMC/muc. p53 nuclear staining was positive only in 3 of 7 invasive IPMCs (43%) and 9 of 21 DCs (43%). DPC4 nuclear expression was positive in almost all cases of non-invasive IPMT, but negative or reduced in 4 of 7 invasive IPMCs (57%), and 14 of 21 DCs (67%). CONCLUSIONS: MUC1 overexpression is considered to be the most sensitive and specific marker of invasive carcinoma, followed by DPC4 and p53 with less sensitivity.     

Intraductal papillary-mucinous tumors of the pancreas: Clinicopathologic features, outcome, and nomenclature. Members of the Pancreas Clinic, and Pancreatic Surgeons of Mayo Clinic

BACKGROUND & AIMS: Intraductal papillary-mucinous tumor (IPMT) of the pancreatic ducts is increasingly recognized. This study investigated if clinical, imaging, or, histological features predicated outcome, formulated a treatment algorithm, and clarified relationships among IPMT, mucinous cystic neoplasms of the pancreas (MCN), and chronic pancreatitis. METHODS: The medical records, radiographs, and pathological specimens of 15 patients with IPMT (dilated main pancreatic duct or branch ducts with mucin overproduction) who were evaluated between October 1983 and January 1994 were reviewed. RESULTS: One patient had hepatic metastases. Fourteen underwent an operation (6 distal pancreatectomy, 4 total pancreatectomy, and 4 pancreaticoduodenectomy); all had dysplastic intraductal epithelium and chronic pancreatitis, whereas 3 had invasive adenocarcinoma. After a median of 25 months, 10 patients were alive; 3 of 4 with malignant and 2 of 11 with benign IPMT died (P < 0.05). Patients with or without carcinoma had similar clinical and radiographic features. A clinical diagnosis of chronic pancreatitis had been made in 9 patients with benign IMPT and in none with malignant IPMT (P < 0.05). CONCLUSIONS: IPMT is a dysplastic and likely precancerous lesion that is frequently diagnosed as chronic pancreatitis and is separate from MCN. Because it is not possible to distinguish noninvasive from invasive IPMT preoperatively, complete surgical excision of the dysplastic process is our treatment of choice whenever appropriate. (Gastroenterology 1996 Jun;110(6):1909-18)     

Immunohistochemical analysis of cyclooxygenase-2 expression in pancreatic tumors

Summary Background A considerable amount of evidence collected from several experimental systems and clinical studies with nonsteroidal Anti-inflammatory drugs (NSAIDs) indicates that Cox-2 may play a major role in colorectal tumorigenesis, but little information about Cox-2 expression in pancreatic tumors is available. In this study, we investigated Cox-2 expression by means of both immunohistochemical analysis and immunoblot analysis in pancreatic tumors. Methods Fifty invasive ductal adenocarcinomas and 26 intraductal papillary-mucinous tumors (IPMTs) were used for immunohistochemical analysis, and five pancreatic cancer tissues and five pancreatic cancer cell lines for immunoblot analysis. Results Cox-2 was expressed in 72% of the invasive ductal adenocarcinomas, 31% of intraductal papillary-mucinous adenocarcinomas, and none of intraductal papillary-mucinous adenomas. The expression rate of Cox-2 in intraductal papillary-mucinous adenocarcinomas was significantly higher than that in intraductal papillary-mucinous adenomas, and that in invasive ductal adenocarcinomas was significantly higher than that in intraductal papillary-mucinous carcinomas. However, there was no significant correlation between Cox-2 expression and the prognosis and clinicopathological factors. Immunoblot analysis identified Cox-2 in all of pancreatic cancer tissues and 60% of cell lines. Conclusion The biological role of cyclooxygenase-2 (Cox-2) in carcinoma cells should be investigated with reference to the cancer progression of the pancreas.     

Synchronous pancreatic serous cystic tumor, intraductal papillary mucinous tumor and gastric carcinoma: report of a case

Synchronous cystic tumors of the pancreas are rarely reported in the literature. We report an unusual case of synchronous pancreatic serous cystic tumor (SCT) and intraductal pancreatic mucinous tumor (IPMT) with concomitant gastric carcinoma. This study highlights the importance of careful intra-operative and pathologic examination for concomitant pancreatic neoplasms.     

Intraductal papillary-mucinous tumor of the pancreas concomitant with ductal carcinoma of the pancreas

Background: Despite the recent progress of diagnostic and therapeutic modalities, the clinical course of patients with ductal carcinoma (DC) of the pancreas remains dismal. Intraductal papillary-mucinous tumor of the pancreas (IPMT) is sometimes accompanied by malignant diseases of the other organs and pancreatic adenocarcinoma. Thus, IPMT may be a potential diagnostic clue to DC of the pancreas at early phase. Methods: Clinico-pathologic findings of 7 Japanese patients with IPMT of the pancreas concomitant with independent DC were examined and compared with those of 69 patients with IPMT alone and of 70 with DC alone. Results: The seven patients corresponded to 9.2% of 76 patients with IPMT and 9.1 % of 77 patients with DC. The seven male patients ranged from 55 to 75 years with a mean of 64.3. DC was synchronous with IPMT in five patients, metachronous to IPMT (4 years after IPMT) in one, and synchronous with IPMT and metachronous to IPMT and DC (7 years after IPMT) in the other. In 4 patients, the presence of IPMT led to the diagnosis of DC. All the 7 IPMTs were of branch type with a mean diameter of 3.0 cm. The IPMT was located in the head of the pancreas in 3, body in 2 and tail in the other 2. All the 7 IPMTs were adenoma with mild dysplasia. Two of the 7 patients with DC had in situ carcinoma, 1 minimally invasive carcinoma and the remaining 4 invasive carcinoma. The mean diameter of seven DCs (3.0 cm) with IPMT were smaller than that of 70 DCs (3.6 cm) (8P = 0.0295). Stage (stage I/II/III/IV = 3/0/3/1) of the seven DCs concomitant with IPMT were significantly earlier than that (stage I/II/III/IV = 5/6/28/31) of the other 70 (p = 0.0203). The survival curve of the 7 patients with IPMT and DC was significantly better than that of the 70 with DC alone (p = 0.0460). Conclusions: Clinicians should pay attention to the possible presence of DC of the pancreas in male patients with intraductal papillary-mucinous adenoma of the pancreas of branch type in their 6th to 8th decades.     

p53 protein expression in intraductal papillary mucinous tumors (IPMT) of the pancreas as an indicator of tumor malignancy

BACKGROUND/AIMS: Intraductal papillary mucinous tumors, as a cystic disease in the pancreas, clinically has a more indolent and favorable course than invasive ductal pancreas carcinoma. However, some cases of intraductal papillary mucinous tumors show invasive and rapid progression like ductal pancreas carcinoma and the prognosis of such patients is sometimes poor. In the current study, we carried out immunohistochemical staining of intraductal papillary mucinous tumor tissues for p53 and investigated whether positive staining indicates tumor malignancies and has a prognostic value for intraductal papillary mucinous tumors. METHODOLOGY: Nineteen (19) patients who underwent pancreatic resection under the diagnosis of intraductal papillary mucinous tumors at the Chiba University Hospital between April 1992 and December 1996 were studied. We performed immunohistochemical staining of p53 as well as of PCNA, Ki-67 and Bcl-2 using their respective antibodies. Pathological findings revealed that 9 cases were intraductal papillary adenoma, 9 were intraductal papillary adenocarcinoma, and one was invasive ductal papillary adenocarcinoma. RESULTS: p53 expression could only be detected in the 1 case with invasive ductal papillary adenocarcinoma. Significant association could not be found between histological features and immunohistochemical staining of PCNA, Ki-67 and Bcl-2. CONCLUSIONS: p53 protein expression could be detected after progression to invasive type of intraductal papillary mucinous tumors. The present results demonstrate that p53 expression might be an indicator of invasive progression in intraductal papillary mucinous tumors, and might represent a surgical indicator of intraductal papillary mucinous tumors.     

Immunohistochemical analysis of cyclooxygenase-2 expression in pancreatic tumors.

BACKGROUND: A considerable amount of evidence collected from several experimental systems and clinical studies with nonsteroidal Anti-inflammatory drugs (NSAIDs) indicates that Cox-2 may play a major role in colorectal tumorigenesis, but little information about Cox-2 expression in pancreatic tumors is available. In this study, we investigated Cox-2 expression by means of both immunohistochemical analysis and immunoblot analysis in pancreatic tumors. METHODS: Fifty invasive ductal adenocarcinomas and 26 intraductal papillary-mucinous tumors (IPMTs) were used for immunohistochemical analysis, and five pancreatic cancer tissues and five pancreatic cancer cell lines for immunoblot analysis. RESULTS: Cox-2 was expressed in 72% of the invasive ductal adenocarcinomas, 31% of intraductal papillary-mucinous adenocarcinomas, and none of intraductal papillary-mucinous adenomas. The expression rate of Cox-2 in intraductal papillary-mucinous adenocarcinomas was significantly higher than that in intraductal papillary-mucinous adenomas, and that in invasive ductal adenocarcinomas was significantly higher than that in intraductal papillary-mucinous carcinomas. However, there was no significant correlation between Cox-2 expression and the prognosis and clinicopathological factors. Immunoblot analysis identified Cox-2 in all of pancreatic cancer tissues and 60% of cell lines. CONCLUSION: The biological role of cyclooxygenase-2 (Cox-2) in carcinoma cells should be investigated with reference to the cancer progression of the pancreas.     

Intraductal papillary mucinous tumor: diagnostic and therapeutic approach

Primary cystic pancreatic neoplasms are rare tumors, with an approximate prevalence of 10% of cystic pancreatic lesions. Most of these lesions correspond to mucinous cystic neoplasm, serous cystoadenoma and intraductal papillary mucinous tumor (IPMT). IPMT is characterized by diffuse dilatation of the main pancreatic duct and/or side branches with inner defects related to mucin or tumor, or mucin extrusion from a patent ampulla. IPMT has a low potential for malignancy, with a low growth rate, a low rate of metastatic spread and postsurgical recurrence. Over the last few years, major advances have been made in the diagnostic and therapeutic management of this tumor.     

Image-diagnostic features of mature cystic teratomas of the pancreas: report on two cases difficult to diagnose preoperatively

This report documents the findings of two rare cases of mature cystic teratoma of the pancreas. Although they could not be diagnosed preoperatively, our retrospective report suggests that the combined diagnosis of ultrasonography (US), enhanced computed tomography (CT), and magnetic resonance cholangiopancreatography (MRCP) might allow differentiation from other cystic lesions such as mucinous cystic tumors (MCTs) and intraductal papillary–mucinous tumors (IPMTs). Since the cystic teratomas were both filled with keratinous and sebaceous material, they were echogenic, appearing as solid masses on US. Enhanced CT showed their cystic nature, with values slightly higher than water, and MRCP revealed defects of internal signals.     

Intraductal mucinous tumors occurring simultaneously in the liver and pancreas

A case of simultaneous intraductal mucinous tumors of the liver and pancreas in a 67-year-old man is described. Abdominal ultrasonography and computed tomography (CT) revealed the presence of cystic lesions with intraluminal septae both in the caudate lobe of the liver and in the uncinate process of the pancreas; these cystic lesions communicated with the hepatic duct and pancreatic duct, respectively. Mucin retention was observed in the cysts, and cholestasis was induced by mucin secretion into the common bile duct. The lesions were resected by left hepatic lobectomy with caudate lobectomy, and segmental pancreatectomy. Both lesions were multilocular cystic tumors with no papillary projections or focal mass effect in their walls. Histologically, both cystic lesions were a mixture of hyperplasia and adenoma lined by low papillary columnar epithelium. There were no cellular or histological features to suggest malignant change. The fibrous intratumor interstitium lacked any mesenchymal or ovarian-like stroma. The hepatic lesion was considered to be of a similar nature to intraductal papillary mucinous tumor (IPMT) of the pancreas. However, the two lesions occurred simultaneously in the liver and pancreas. This case is of interest in regard to the diagnosis and management of mucinous hepatopancreatobiliary lesions. Received: March 16, 2001 / Accepted: September 14, 2001     

Surgical treatment of intraductal papillary-mucinous tumor (IPMT) of the pancreas: operative indications based on surgico-pathologic study focusing on invasive carcinoma derived from IPMT

Background/Purpose. Between 1979 and 2000, 51 patients with intraductal papillary-mucinous tumor (IPMT) of the pancreas underwent surgical resection. Methods. The patients were reviewed to disclose the surgical pathology of invasive carcinoma derived from IPMT and to determine the surgical indications for IPMT on the basis of the pathologic findings. Results. The incidence of invasive carcinoma derived from IPMT according to the localization of the tumor was as follows: 4/9 (44%) in the main pancreatic duct (MPD type), 4/9 (44%) showing ductal spread from the MPD to branch ducts (mixed type), and 2/33 (6%) in the 2 branch duct (branch type). The maximal size of the intraductal spread of invasive carcinomas (8 of 18 cases in the MPD and mixed type together and 2 of 33 cases in the branch type) was as follows: 6/8 (75%) in the MPD and mixed type were over 6?cm in size, and the 2-branch-type invasive carcinomas were within the 3-cm size range. Conclusions. We concluded that for both invasive and noninvasive IPMTs, surgical resection was necessary for any MPD or mixed-type IPMTs, and that surgical resection was appropriate for branch-type lesions larger than or equal to 3?cm in diameter, or for lesions smaller than 3?cm showing rapid growth on clinical images.