Follicular dendritic cell sarcoma arising from the lymph node of the pancreatic head: a case report with literature review.

A 72-year-old man was referred to our hospital for the examination of a pancreatic head mass. Abdominal computed tomography revealed a contrasted 8-cm-diameter tumor extending from the dorsal pancreatic head to the porta hepatis. The preoperative diagnosis was challenging due to the absence of specific imaging findings and the inability to perform a biopsy. Positron emission tomography/computed tomography and diffusion-weighted imaging suggested a malignant tumor originating from the organs surrounding the pancreatic head. Subtotal stomach-preserving pancreaticoduodenectomy with regional lymph node dissection was performed, as dissection from the pancreatic head proved unfeasible. Pathological examination identified the tumor as an enlarged lymph node consisting of pleomorphic large cells forming clusters, positive for follicular dendritic cell markers cluster of differentiation (CD) 21 and CD23. No evidence of tumor capsule infiltration, other organ infiltration, or metastasis to other lymph nodes was observed. The final diagnosis was nodal follicular dendritic cell sarcoma (FDCS) originating from the pancreatic head lymph nodes. No recurrence occurred at 3 years postoperatively with no postoperative treatment. Intraperitoneal nodal FDCS is extremely rare, and occasionally, it can lead to postoperative recurrence and progression. It is crucial to differentiate neoplastic lymph node enlargement around the pancreatic head from nodal FDCS.

Multiple endocrine neoplasia type 1 with Zollinger-Ellison syndrome: clinicopathological analysis of a Japanese family with focus on menin immunohistochemistry.

Background: Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by the occurrence of multiple epithelial neuroendocrine tumors (NETs) and non-NETs in various organs. MEN1 encodes a 610-amino acid-long tumor suppressor protein, menin. The optimal treatment for multiple tumors, identification of the most critical tumors for patient prognosis, and menin immunohistochemistry findings remain controversial. Therefore, we aimed to elucidate these issues through a histological analysis of tumors and tumor-like lesions in a Japanese family, comprising a father and his two sons, who had MEN1 with Zollinger-Ellison syndrome (ZES). Patients and methods: All family members had a germline alteration in exon 10, c.1714-1715 del TC of MEN1, and exhibited multiple synchronous and metachronous tumors. The patients had pulmonary NETs, hyperparathyroidism, hypergastrinemia, pituitary adenomas, pancreaticoduodenal NETs, adrenocortical adenoma with myelolipoma, nodular goiter of the thyroid, lipomas, and angiofibroma. Most tumors were resected and histologically examined. We compared their clinical courses and tumor histology, and conducted menin immunohistochemistry (IHC). Results: Two patients died of pulmonary NET G2. One patient who underwent pancreaticoduodenectomy was cured of ZES; however, the two other patients who did not undergo pancreaticoduodenectomy suffered persistent ZES despite treatment with octreotide. Menin IHC revealed varying NET intensities, ranging from positive to negative stains. Conclusion: Pancreaticoduodenectomy is the most effective treatment for ZES. Long-term follow-up is essential for pulmonary NET G2 owing to the risk of distant metastasis and/or multiplicity. Moreover, the variability of menin IHC in MEN1-related tumors may indicate the pattern of tumor formation rather than the diagnostic utility of menin in MEN1.

Exploration of Malignant Characteristics in Neoadjuvant Chemotherapy-Resistant Rectal Cancer, Focusing on Extramural Lesions.

BACKGROUND: Extramural vascular invasion (EMVI) and tumor deposits (TD) are poor prognostic factors in rectal cancer (RC), especially when resistant to neoadjuvant chemotherapy (NAC). We aimed to define differential expression in NAC responders and non-responders with concomitant EMVI and TD. METHODS: From 52 RC surgical patients, post-NAC resected specimens were extracted, comprising two groups: cases with residual EMVI and TD (NAC-resistant) and cases without (NAC-effective). Proteomic analysis was conducted to define differential protein expression in the two groups. To validate the findings, immunohistochemistry was performed in another cohort that included 58 RC surgical patients. Based on the findings, chemosensitivity and prognosis were compared. RESULTS: The NAC-resistant group was associated with a lower 3-year disease-free survival rate than the NAC-effective group (p = 0.041). Discriminative proteins in the NAC-resistant group were highly associated with the sulfur metabolism pathway. Among these pathway constituents, selenium-binding protein 1 (SELENBP1) expression in the NAC-resistant group decreased to less than one-third of that of the NAC-effective group. Immunohistochemistry in another RC cohort consistently validated the relationship between decreased SELENBP1 and poorer NAC sensitivity, in both pre-NAC biopsy and post-NAC surgery specimens. Furthermore, decrease in SELENBP1 was associated with a lower 3-year disease-free survival rate (p = 0.047). CONCLUSIONS: We defined one of the differentially expressed proteins in NAC responders and non-responders, concomitant with EMVI and TD. SELENBP1 was suspected to contribute to NAC resistance and poor prognosis in RC.

Three-dimensional analysis of perineural invasion in extrahepatic cholangiocarcinoma using tissue clearing.

Perineural invasion (PNI) is a characteristic invasion pattern of distal cholangiocarcinoma (DCC). Conventional histopathologic examination is a challenging approach to analyze the spatial relationship between cancer and neural tissue in full-thickness bile duct specimens. Therefore, we used a tissue clearing method to examine PNI in DCC with three-dimensional (3D) structural analysis. The immunolabeling-enabled 3D imaging of solvent-cleared organs method was performed to examine 20 DCC specimens from five patients and 8 non-neoplastic bile duct specimens from two controls. The bile duct epithelium and neural tissue were labeled with CK19 and S100 antibodies, respectively. Two-dimensional hematoxylin/eosin staining revealed only PNI around thick nerve fibers in the deep layer of the bile duct, whereas PNI was not identified in the superficial layer. 3D analysis revealed that the parts of DCC closer to the mucosa exhibited more nerves than the normal bile duct. The nerve fibers were continuously branched and connected with thick nerve fibers in the deep layer of the bile duct. DCC formed a tubular structure invading from the epithelium and extending around thin nerve fibers in the superficial layer. DCC exhibited continuous infiltration around the thick nerve fibers in the deep layer. This is the first study using a tissue clearing method to examine the PNI of DCC, providing new insights into the underlying mechanisms.

Effect of problem-based learning tutor seniority on medical students' emotions: an equivalence study.

BACKGROUND: The effectiveness of peer learning has been recognized and discussed by many scholars, and implemented in the formal curriculums of medical schools internationally. However, there is a general dearth of studies in measuring the objective outcomes in learning. METHODS: We investigated the objective effect of near-peer learning on tutee's emotions and its equivalence within the formal curriculum of a clinical reasoning Problem Based Learning session in a Japanese medical school. Fourth-year medical students were assigned to the group tutored by 6th-year students or by faculties. The positive activating emotion, positive deactivating emotion, negative activating emotion, negative deactivating emotion, Neutral emotion were measured using the Japanese version of the Medical Emotion Scale (J-MES), and self-efficacy scores were also assessed. We calculated the mean differences of these variables between the faculty and the peer tutor groups and were statistically analyzed the equivalence of these scores. The equivalence margin was defined as a score of 0.4 for J-MES and 10.0 for the self-efficacy score, respectively. RESULTS: Of the 143 eligible participant students, 90 were allocated to the peer tutor group and 53 were allocated to the faculty group. There was no significant difference between the groups. The 95% confidence interval of the mean score difference for positive activating emotions (-0.22 to 0.15), positive deactivating emotions (-0.35 to 0.18), negative activating emotions (-0.20 to 0.22), negative deactivating emotions (-0.20 to 0.23), and self-efficacy (-6.83 to 5.04) were withing the predetermined equivalence margins for emotion scores, meaning that equivalence was confirmed for these variables. CONCLUSIONS: Emotional outcomes were equivalent between near-peer PBL sessions and faculty-led sessions. This comparative measurement of the emotional outcomes in near-peer learning contributes to understanding PBL in the field of medical education.

18F­fluorodeoxyglucose positron emission tomography predicts recurrence and histological grade of extrahepatic bile duct cancer.

Malignant tumors in cholangiocarcinoma are diagnosed and staged using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) and clinical analysis. However, comprehensive analysis, including pathological analysis, has not yet been sufficiently performed. In the present study, the maximum standardized uptake value (SUVmax) was calculated using FDG-PET and its relationship with clinicopathological factors was analyzed. The present study included 86 patients who underwent preoperative FDG-PET/computed tomography (CT) and did not receive chemotherapy among 331 patients with hilar and distal cholangiocarcinoma. Receiver operating characteristic analysis with recurrence events was used to determine the SUVmax cutoff of 4.9. Immunohistochemical staining of glucose transporter 1 (Glut1), hypoxia-inducible factor-1α and Ki-67 was performed for pathological analysis. The standardized uptake value (SUV)-high group (SUVmax ≥4.9) had a higher postoperative recurrence rate (P<0.046) and higher Glut1 and Ki-67 expression rates (P<0.05 and P<0.0001, respectively). Furthermore, SUVmax and Glut1 expression (r=0.298; P<0.01) and SUVmax and Ki-67 expression rates (r=0.527; P<0.0001) were positively correlated. The preoperative measurement of SUVmax by PET-CT is useful in predicting recurrence as well as cancer malignancy.

Use of time­density curves of dynamic contrast­enhanced computed tomography for determination of the histological therapeutic effects of neoadjuvant chemotherapy for pancreatic ductal adenocarcinoma.

The present study aimed to investigate the histological changes caused by neoadjuvant chemotherapy (NAC) for pancreatic ductal adenocarcinoma (PDAC), and to demonstrate the use of time­density curves (TDCs) of dynamic contrast­enhanced computed tomography (CECT) for determination of the histological therapeutic effects of NAC for PDAC. A total of 96 patients with PDAC were examined; 46 underwent NAC (NAC group) and 50 did not undergo NAC (non­NAC group). Based on histological therapeutic effect and using the area of residual tumor (ART) grading system, the NAC group was divided into low­responders and high­responders. Histological analysis was used to evaluate the densities of cancer cells, cancer­associated fibroblasts (CAFs), microvessels and stromal collagen fibers in the NAC and non­NAC groups. Radiological analysis was used to evaluate the TDCs of three slopes of the NAC group, namely slopes between the non­contrast and arterial phases (δ1 and δ1'), between the arterial and portal phases (δ2 and δ2'), and between the portal and equilibrium phases (δ3 and δ3'). δ1­Î´3 were before NAC, whereas δ1'­Î´3' were after NAC. Changes in δ1, δ2 and δ3 before and after NAC were denoted as δδ1 (=δ1'­Î´1), δδ2 (=δ2'­Î´2) and δδ3 (=δ3'­Î´3). ART grading system, histological examination and radiological examination data were also statistically analyzed. Histological examination revealed a significant decrease in cancer cells and CAFs, and a significant increase in stromal collagen fibers due to NAC (P<0.01). Radiological examination revealed that δ1' was significantly higher than δ1 in low­responders (P<0.05), whereas δ2' was significantly lower than δ2 in high­responders (P<0.01). δδ2 was significantly lower and δδ3 was significantly higher in high­responders than in low­responders (P<0.01 and P<0.05, respectively). Receiver operating characteristic curve showed that δδ2 and δδ3 were effective indicators of the histological therapeutic effect of NAC. In conclusion, the TDC of dynamic CECT may be useful for determining the histological therapeutic effect of NAC for PDAC.

Adapting the Motivated Strategies for Learning Questionnaire to the Japanese Problem-Based Learning Context: A Validation Study.

The COVID-19 pandemic has greatly changed medical education, and medical trainees' self-regulation has become more emphasized. In Japan, the concept of self-regulated learning has not been fully applied in health profession education due to a lack of effective measurement tools. We aimed to validate the translated Japanese version of the Motivated Strategies for Learning Questionnaire in the context of Problem-Based Learning (J-MSLQ-PBL). The questionnaire employs a seven-point Likert-type scale with 81 items and is categorized into two sections: motivation and learning strategies. An exploratory factor analysis (EFA) was conducted by using Promax rotation to examine the factor structure of the scale, using the collected data from 112 Japanese medical students. Factor extraction was based on a scree plot investigation, and an item was accepted when the factor loading was ≥0.40. In the motivation section, the extracted factors from the EFA were well aligned with the subscales of the original MSLQ, including "Self-Efficacy for Learning and Performance", "Task Value", "Self-Efficacy for Learning and Performance", "Test Anxiety", "Extrinsic Goal Orientation", and "Intrinsic Goal Orientation". In the learning strategies, the extracted factors poorly matched the structure of the original subscales. This discrepancy could be explained by insufficient translation, the limited sample size from a single medical school, or cross-cultural differences in learning strategies between Western and Japanese medical students. Only the motivation part of the J-MSLQ-PBL should be implemented to measure the competency elements of self-regulated learning in Japan.

A case of serous cystic neoplasm with tumor growth acceleration leading to extrapancreatic invasion.

Serous cystic neoplasm (SCN) is a potentially malignant and invasive disease. However, there are no established guidelines regarding the surgical management of SCN. Here, we report a case of SCN with jejunal invasion that ultimately required a distal pancreatectomy with partial resection of the jejunum. The patient was a 65-year-old female who was referred to our department after a diagnosis of SCN in the pancreatic tail. CT and MRI showed a 75-mm multifocal cystic mass with calcifications; the splenic vein and left adrenal vein were entrapped within the tumor. Furthermore, the tumor was in contact with the beginning of the jejunum. Finally, she underwent a posterior radical antegrade modular pancreatosplenectomy with a partial wedge-shaped resection of the jejunum. Histological findings indicated serous cystadenoma. In addition, the tumor cells were found to have infiltrated the jejunal muscularis propria in some areas, suggesting that the tumor had malignant potential. Currently, 14 months have passed since surgery and there is no evidence of metastasis or recurrence. Surveillance and the decision to perform surgical resection should be made based on tumor size and growth rate to avoid malignant transformation as well as to provide SCN patients with organ-sparing, less invasive surgery.

Case Report: A Giant Epignathus with a Well-Developed Skeleton of Head and Neck.

Epignathus is an extremely rare teratoma found in the oral cavity or oropharyngeal region of newborns, whose pathogenesis is poorly understood. We describe a giant epignathus arising from the oropharynx in a newborn. The giant tumor completely obstructed the airway of the newborn resulting in death. Histological and radiological examination of the tumor reveals the presence of a remarkably well-developed skeleton of the head and neck. A row of teeth, the axis and atlas, thyroid and salivary glands, trachea, and cerebral tissue are all detected within the tumor. These findings suggest that the epignathus is fetus-in-fetu which is considered a type 0 germ cell tumor in accordance with current literature.

Testicular teratomagenesis from primordial germ cells with overexpression of germinal center-associated nuclear protein.

Testicular teratomas are the major histologic type of testicular germ cell tumors and their incidence continues to grow. Moreover, teratomas can develop from undifferentiated cells in induced pluripotent stem (iPS) cell transplantation therapy, seriously hampering the progress of regenerative medicine. Germinal center-associated nuclear protein (GANP) is thought to be important to the biogenetic control of primordial germ cells and is among the genes susceptible to testicular germ cell tumors. Thus, we analyzed the expression of GANP in human testicular postpubertal-type teratomas and established a novel mouse model to reveal the association between GANP and teratomagenesis. We analyzed 31 cases of human testicular postpubertal-type teratomas and, in all cases, GANP was overexpressed. The aberrant expression was also detected in germ cell neoplasia in situ accompanied by the teratoma. GANP expression was particularly high in the epithelia of the epidermis, cutaneous appendages, and trachea-like ciliated epithelium. To further clarify the association between GANP and teratomagenesis, we established a novel teratomagenesis mouse model (CAG-ganpTg mice). In the GANP-teratoma mice, GANP-overexpressing teratomas were more frequent at the testes and the middle portion of the uterus than has been seen in the previously established mouse models. In conclusion, GANP is overexpressed in testicular postpubertal-type teratomas and is an essential teratomagenic factor. We also found that CAG-ganpTg mice are useful mouse models of teratomagenesis that mimics human midline teratomas and that teratomas may originate from the overexpression of GANP in primordial germ cells.

An autopsy case of amyotrophic lateral sclerosis with striatonigral and pallidoluysian degeneration and cat's-eye-shaped neuronal nuclear inclusions.

We report the case of a Japanese woman with sporadic amyotrophic lateral sclerosis (ALS) of 28 months' duration who died at the age of 66 years. Postmortem examination revealed moderate loss of neurons and phosphorylated TDP-43 (p-TDP-43)-immunoreactive neuronal and glial cytoplasmic inclusions in the upper and lower motor neurons. Additionally, marked neuronal loss was observed in the neostriatum, globus pallidum, subthalamic nucleus, and substantia nigra. p-TDP-43-immunoreactive inclusions were frequently found in these areas. Neuronal loss and TDP-43 pathology in the motor, striatonigral, and pallidoluysian systems were predominant on the right side. Moreover, p-TDP-43-immunoreactive cat's-eye-shaped neuronal nuclear inclusions (NNIs) were observed in the affected lesions. NNIs in the striatonigral system were also positive for valosin-containing protein (VCP). We diagnosed the patient as having ALS with striatonigral and pallidoluysian degeneration. Patients with ALS rarely experience pallido-nigro-luysian degeneration. To our best knowledge, only one case of ALS combined with striatonigral and pallidoluysian degeneration has been reported. Neuronal loss in the striatonigral and/or pallidoluysian systems has also been reported in patients with ALS with multisystem degeneration accompanied by long-term use of an artificial respirator. Based on these findings, a possibility of an extremely rare subtype of ALS demonstrating selective loss of neurons in the striatonigral and pallidoluysian systems exists; another possibility is that this type could be an early stage or forme fruste of ALS with multisystem degeneration. Although VCP-positive cat's-eye-shaped NNIs have been reported in spinocerebellar ataxia type-2 cases, our case report presents VCP-positive NNIs in a patient with ALS for the first time.

Heterogeneity of metabolic adaptive capacity affects the prognosis among pancreatic ductal adenocarcinomas.

BACKGROUND: Evolutionary cancer has a supply mechanism to satisfy higher energy demands even in poor-nutrient conditions. Metabolic reprogramming is essential to supply sufficient energy. The relationship between metabolic reprogramming and the clinical course of pancreatic ductal adenocarcinoma (PDAC) remains unclear. We aimed to clarify the differences in metabolic status among PDAC patients. METHODS: We collected clinical data from 128 cases of resectable PDAC patients undergoing surgery. Sixty-three resected tissues, 15 tissues from the low carbohydrate antigen 19-9 (CA19-9), 38-100 U/mL, and high CA19-9, > 500 U/mL groups, and 33 non-tumor control parts, were subjected to tandem mass spectrometry workflow to systematically explore metabolic status. Clinical and proteomic data were compared on the most used PDAC biomarker, preoperative CA19-9 value. RESULTS: Higher CA19-9 levels were clearly associated with higher early recurrence (p < 0.001), decreased RFS (p < 0.001), and decreased DSS (p = 0.025). From proteomic analysis, we discovered that cancer evolution-related as well as various metabolism-related pathways were more notable in the high group. Using resected tissue immunohistochemical staining, we learned that high CA19-9 PDAC demonstrated aerobic glycolysis enhancement, yet no decrease in protein synthesis. We found a heterogeneity of various metabolic processes, including carbohydrates, proteins, amino acids, lipids, and nucleic acids, between the low and the high groups, suggesting differences in metabolic adaptive capacity. CONCLUSIONS: Our study found metabolic adaptation differences among PDAC cases, pertaining to both cancer evolution and the prognosis. CA19-9 can help estimate the metabolic adaptive capacity of energy supply for PDAC evolution.

The clinical and neuropathological picture of adult neuronal intranuclear inclusion disease with no radiological abnormality.

In typical adult neuronal intranuclear inclusion disease (NIID) with predilection for the basal ganglia or cerebral cortex, not only neurons but also glial cells harbor intranuclear inclusions. In addition, these inclusions are present in the peripheral autonomic nervous system, visceral organs and skin. In NIID cases with an expansion of GGC repeats in the 5'-untranslated region (5'-UTR) of the Notch 2 N-terminal like C (NOTCH2NLC) gene, these repeats are located in an upstream open reading frame (uN2C) and result in the production of a polyglycine-containing protein called uN2CpolyG. Typically, patients with adult NIID show high-intensity signals at the corticomedullary junction on diffusion-weighted brain magnetic resonance imaging. We report a case of adult NIID in a 78-year-old Japanese male, who suffered from mild, non-progressive tremor during life but showed no radiographic abnormalities suggestive of adult NIID. Pathologically, ubiquitin-, p62- and uN2CpolyG-positive neuronal intranuclear inclusions were particularly frequent in the hippocampal formation, but were also seen in the enteric plexuses, kidney and cardiac muscles. By contrast, glial intranuclear inclusions were barely evident in the affected regions. The present case also had an immunohistochemical profile differing from that of typical adult NIID. The findings in this case suggest that adult NIID can show clinical, radiographic and pathological heterogeneity.

Eukaryotic initiation factor 2 signaling behind neural invasion linked with lymphatic and vascular invasion in pancreatic cancer.

Perineural invasion (PNI) is a typical poor prognostic factor in pancreatic ductal adenocarcinoma (PDAC). The mechanisms linking PNI to poor prognosis remain unclear. This study aimed to clarify what changes occurred alongside PNI in PDAC. A 128-patient cohort undergoing surgery for early-stage PDAC was evaluated. Subdivided into two groups, according to pathological state, a pancreatic nerve invasion (ne) score of less than three (from none to moderate invasion) was designated as the low-grade ne group. The high-grade (marked invasion) ne group (74 cases, 57.8%) showed a higher incidence of lymphatic metastasis (P = 0.002), a higher incidence of early recurrence (P = 0.004), decreased RFS (P < 0.001), and decreased DSS (P < 0.001). The severity of lymphatic (r = 0.440, P = 0.042) and venous (r = 0.610, P = 0.002) invasions was positively correlated with the ne score. Tumors having abundant stroma often displayed severe ne. Proteomics identified eukaryotic initiation factor 2 (EIF2) signaling as the most significantly enriched pathway in high-grade ne PDAC. Additionally, EIF2 signaling-related ribosome proteins decreased according to severity. Results showed that PNI is linked with lymphatic and vascular invasion in early-stage PDAC. Furthermore, the dysregulation of proteostasis and ribosome biogenesis can yield a difference in PNI severity.

Time density curve of dynamic contrast-enhanced computed tomography correlates with histological characteristics of pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an infiltrative growth pattern with intense desmoplastic stroma comprised of cancer-associated fibroblasts (CAFs). Additionally, the histological characteristics are considered to play a vital role in the poor prognosis of PDAC. However, the density of cancer cells, degree of desmoplasia and vascular proliferation varies in individual cases. We hypothesized that preoperative radiological images would reflect histological characteristics, such as cancer cell density, CAF density and microvessel density. To clarify the association between the histological characteristics and radiological images of PDAC, the cancer cell density, CAF density and microvessel density from surgical specimens were measured with immunostaining, and the time density curve of dynamic contrast-enhanced computed tomography (CECT) was analyzed. Overall, the initial slope between non-enhanced and arterial phases was correlated with microvessel density, and the second slope between arterial and portal phases was correlated with CAF and cancer cell densities. In conclusion, the present study suggested the possibility of estimating cancer cell, CAF and microvessel densities using the TDC of dynamic CECT.

A case report of mucinous adenocarcinoma derived from intra-ampullary papillary-tubular neoplasm with a malignant course.

BACKGROUND: Intra-ampullary papillary-tubular neoplasm (IAPN) has been classified as a Vater papillary tumor. The prognosis of IAPN is generally relatively good. Here, we describe a patient with a mucinous adenocarcinoma cluster in the Vater papilla of IAPN origin. CLINICAL PRESENTATION: The patient was a 66-year-old man who was admitted to our hospital after a diagnosis of pancreatic head carcinoma based on a pancreatic duct dilatation found on abdominal ultrasound. CT showed a 40 mm lesion in the pancreatic head and expansion of the main pancreatic duct to a maximum diameter of 9 mm on the caudal side of the lesion. The extrahepatic bile duct had also expanded to a maximum diameter of 8 mm. PET/CT showed fluorodeoxyglucose (FDG) accumulation of SUVmax 6.02 that corresponded to the tumor in the pancreatic head, though it did not suggest distant metastasis. The patient was diagnosed with pancreatic head carcinoma T3 N0 M0 Stage IIA and underwent a pancreaticoduodenectomy. Pathology indicated that the tumor in the pancreatic head was a benign inflammatory lesion. On the other hand, the papillotubular tumor pervading the lumen in the duodenal papillary common channel met the criteria for IAPN, and a mucinous adenocarcinoma cluster found in the surrounding stroma suggested malignant transformation of IAPN. No metastasis to lymph nodes was demonstrated. With regard to the mucus phenotype of each lesion, the IAPN was MUC2 and MUC5AC positive, while the mucinous adenocarcinoma was MUC2-positive and MUC5AC-negative. In addition, CD10 was negative in both lesions, suggesting that mucus transformation from the gastric type to the intestinal type was a key element. A blood test 10 months after surgery showed increased CA19-9 (105 U/mL) and CEA (7.1 ng/mL). Abdominal CT showed multiple cystoid nodes in the liver, which were diagnosed as multiple liver metastases of mucinous adenocarcinoma transformed from the IAPN. CONCLUSIONS: We reported a case with IAPN that developed in the Vater papilla, which took an extremely malignant course. IAPN generally has a good prognosis, but it is important to understand that a malignant course may occur.