A case of high-grade mucinous tubular and spindle cell carcinoma.

Mucinous tubular and spindle cell carcinoma (MTSCC) is a rare renal cell carcinoma that initially presents as low-grade renal cell carcinoma. However, cases of MTSCC with high-grade histology and poor prognosis have been reported. Here, we report a case of MTSCC with high-grade histological features and metastasis. A 77-year-old woman consulted a hospital following frequent and painful micturition. Computed tomography scan revealed a tumor of the left kidney. First, chemotherapy was performed, with no effects. Therefore, nephrectomy was subsequently performed. Histologically, the tumor showed the features of MTSCC with sarcomatoid component. Metastasis of the tumor into the lymph node was also observed. Although adjuvant chemotherapy was performed after nephrectomy, metastasis to the lungs and bone and local recurrence was observed. The patient is still alive 2 years after nephrectomy with metastasis and recurrence of the tumor. High-grade MTSCC shows a relatively poor prognosis, specifically MTSCC with metastasis upon nephrectomy.

Extra-gastrointestinal stromal tumor with a large cyst.

Gastrointestinal stromal tumors (GISTs) arising at sites other than the alimentary tract are rare, and they are called extra-GISTs (EGISTs). We report a case of a large EGIST forming a cyst, probably arising in the mesentery of the transverse colon. A 64-year-old Japanese man presented to a hospital with an abdominal tumor forming a large cyst. Intraoperatively, the tumor was neither present in nor in contact with the alimentary tract. It was present in the mesentery of the transverse colon and was attached to the greater omentum and peritoneum, immediately anterior to the body of the pancreas. The tumor was resected with the spleen and a part of the pancreas. Histological examination of the tumor revealed that it belonged to the high-risk category of cystic EGISTs.

Hepatic epithelioid hemangioendothelioma with metastasis to the mesentery of the small intestine: A case report.

Epithelioid hemangioendothelioma (EHAE) is a vascular tumor which, due to its rarity, is often misdiagnosed as other hepatic tumors based on radiological characteristics. We herein report a case of EHAE in the liver and the mesentery of the small intestine. A 64-year-old asymptomatic woman was admitted to the hospital due to a hepatic tumor identified using computed tomography (CT). An enhanced CT scan revealed multiple tumors in the liver and a tumor in the mesentery. One of the hepatic tumors and the mesenteric tumor were resected and histologically examined. The two tumors exhibited similar histological characteristics and were diagnosed as EHAE. When multiple tumors are found in the liver, EHAE should be included in the differential diagnosis, as the prognosis of EHAE differs from that of carcinoma or benign tumors.

Nephrogenic adenoma in elderly patients: Three case reports.

Nephrogenic adenoma (NA), referred to as nephrogenic metaplasia, is a rare benign lesion of the urinary tract. NA is histologically characterized by tubular and papillary formations lined by low cuboidal to columnar epithelial cells. NA is also immunohistochemically characterized by positivity for paired box (PAX) 2, PAX8 and cytokeratin 7, and negative for p63 and prostate-specific antigen. In this study, we present 3 cases of NA arising in the urinary bladder of elderly male patients with predisposing factors: patient 1 had undergone transurethral lithotripsy due to a ureteral stone; patient 2 had undergone transurethral resection of a urothelial carcinoma in the urinary bladder; and patient 3 had been treated with Bacillus-Calmettle-Guérin due to a urothelial carcinoma in the urinary bladder. The characteristics of the NAs of our 3 cases were histologically and immunohistologically consistent with previously reported cases, although 1 patient exhibited a pseudoinvasive pattern. Since NA is a tumor-like benign lesion, it should be clearly differentiated morphologically and immunohistologically from other tumors arising in the urinary tract and from invasion by prostate cancer.

The role of CD5 expression in thymic carcinoma: possible mechanism for interaction with CD5+ lymphoid stroma (microenvironment).

AIMS: Most thymic carcinomas express the lymphocyte marker CD5 aberrantly. This study was performed to examine the role of the self-reactive CD5 antigen in thymic carcinoma. METHODS AND RESULTS: We examined CD5 expression in thymic carcinoma in relation to the lymphoid stroma. All cases of thymic carcinoma examined expressed CD5. A number of CD5(+) lymphocytes were also present in the stroma of thymic carcinoma. The CD5(+) tumour areas were predominantly in contact with the lymphoid stroma, and the expression level was significantly lower in tumour cells than lymphocytes. Although p53 and Bcl-2 expression levels were significantly higher in thymic carcinoma than normal thymic epithelial cells (TECs), they did not differ between CD5(+) and CD5(-) areas. E-cadherin expression in thymic carcinoma was comparable with that of normal TECs, and it also did not differ between these areas. In contrast, both Ki-67 index and mitotic activity were significantly higher in thymic carcinoma than normal TECs, and they were significantly higher in CD5(+) than CD5(-) areas. CONCLUSIONS: CD5 may be induced by interaction with CD5(+) lymphoid stroma, and may be related to tumour proliferation. CD5 induction may also be a significant and/or specific effect of the tumour microenvironment of the thymus.

Possible involvement of Toll-like receptor 7 in the development of type 1 autoimmune pancreatitis.

BACKGROUND: High serum immunoglobulin G4 (IgG4) levels and IgG4-positive plasma cell infiltration are characteristic of type 1 autoimmune pancreatitis (AIP). It is unclear whether innate immunity is a cause of type 1 AIP; the possible involvement of microbial infection has been suggested in its pathogenesis. To clarify the pathogenesis of type 1 AIP, we investigated Toll-like receptors (TLRs) in type 1 AIP patients. METHODS: We studied nine cases of type 1 AIP with ten cases of alcoholic chronic pancreatitis (ACP) and three of the samples from non-tumorous lesion of neuroendocrine tumor (NET) as control subjects. We counted the number of TLR1-11-positive cells immunohistochemically stained with anti-TLR1-11 antibodies. To identify TLR-positive cells in pancreata from type 1 AIP patients, we used a double-immunofluorescence method and counted the numbers of identifiable CD68-, CD163-, CD123-, and CD20-positive cells. RESULTS: In type 1 AIP, TLR7 (8.815 ± 1.755), TLR8 (3.852 ± 1.489), and TLR10 (3.852 ± 0.921) were highly expressed. Only the ratio of TLR7 per monocyte was significantly higher in type 1 AIP (0.053 ± 0.012) than in ACP (0.007 ± 0.004; p < 0.01) and non-tumorous lesion of NET (0.000 ± 0.000; p < 0.01). In type 1 AIP, the CD163 to TLR7 ratio (0.789 ± 0.031) was significantly higher both than that of CD123 to TLR7 ratio (0.034 ± 0.006; p < 0.001) and CD20 to TLR7 ratio (0.029 ± 0.010; p < 0.001). CONCLUSIONS: TLR7 might be key pattern-recognition receptors involved in the development of type 1 AIP.

Solitary fibrous tumor of the kidney with focus on clinical and pathobiological aspects.

Renal solitary fibrous tumor (SFT) is a rare, and a large scale study on this topic is lacking to date. In this article, we summarize the previously reported cases. The symptoms and signs resemble those of renal cell carcinoma, including hematuria, flank/abdominal/lumbar pain and palpable abdominal mass. Grossly, the tumor demonstrates a well-circumscribed solid mass. Microscopically, the tumor consists of fusiform or ovoid spindle cells and a various amounts of collagen bundles with patternless, storiform, or fascicular arrangements with an occasional hemangiopericytomatous pattern. Immunohistochemically, CD34, CD99 and bcl-2 are often detected. Ultrastructurally, tumor cells contain irregular nuclei, prominent Golgi apparatus, branching rough endoplasmic reticulum, variable numbers of mitochondria. Surgical resection is considered to be the gold standard therapy. Most of renal SFT are benign, but cases of approximately 10 to 15% behave in an aggressive fashion. All patients need to be on long-term follow-up because clinical behavior is rather unpredictable. As the molecular genetic study of renal SFTs is lacking, a large scale study will be desirable in the future.

Adenocarcinoma with adenoma in the jejunum suggesting an adenoma-carcinoma sequence in the small bowel: A case report.

Other than that in the duodenum, adenocarcinoma in the small bowel is rare. The present study describes a case of adenocarcinoma with adenoma in the jejunum. A 70-year-old male was admitted to hospital due to dehydration induced by abdominal discomfort and difficulty with oral intake. Computed tomography revealed a tumor in the upper side of the jejunum, which was subsequently resected. The tumor contained adenocarcinoma and adenoma. The protein expression of p53 and Ki-67 was analyzed in the normal mucosa, adenoma and adenocarcinoma. The number of epithelial cells expressing p53 and Ki-67 was found to increase in the adenoma tissue compared with that in the normal mucosa. In the adenocarcinoma tissue, the number of cells expressing p53 and Ki-67 further increased, suggesting that an adenoma-adenocarcinoma sequence may occur in the small bowel, similar to that observed in the large bowel.

Placental mesenchymal dysplasia, a case of intrauterine sudden death.

Placental mesenchymal dysplasia (PMD) is a rare condition presenting with enlarged, multicystic placenta like molar changes. Although PMD usually features a normal fetus and the pregnancy often extends into the third trimester, PMD is clinically significant lesion with high rates of FGR, IUFD, and is associated with Beckwith-Wiedemann syndrome (BWS). We report a 30-year old woman at her first pregnancy with intrauterine sudden death at 31 weeks of gestation. The vesicular lesion in her uterus was detected at 10 weeks on ultrasound. The fetus was normal size without any anomaly on ultrasound and normal trophoblastic vascularization by Doppler study during the pregnancy. As the pregnancy advanced, the vesicular lesion decreased in size and no fetal abnormalities were detected. At 28 weeks of gestation an ultrasound detected dilated periumbilical chorionic vessels. We didn't detect severe FGR or abnormal trophoblastic vascularization. At 31 weeks of gestation an intrauterine sudden death of a normal-sized fetus without any anomaly occurred. The placenta was enlarged, and microscopic morphology confirmed a diagnosis of PMD. The chorionic vessels were cirsoid, dilated and tortuous. We determined the rupture of expanded periumbilical chorionic vessels led to fetal death.

Pathological outcomes of Japanese men eligible for active surveillance after radical prostatectomy.

BACKGROUND: The aim of this study was to analyze the pathological features of prostatectomy specimens from patients with low-risk prostate cancer eligible for active surveillance (AS) and evaluate preoperative data suitable for predicting upstaged (≥pT3) or upgraded disease (Gleason score of ≥7), defined as 'reclassification'. METHODS: A retrospective analysis of 521 consecutive radical prostatectomy procedures (January 2005 through to December 2011) performed at our institution without neoadjuvant hormonal therapy was performed. Eighty-four patients fulfilled the following criteria-clinical T1 or T2 disease, prostate-specific antigen (PSA) level of ≤10 ng/ml, one or two positive biopsies, and Gleason score of <7. Clinicopathological features at diagnosis were compared between patients with and without reclassification after radical prostatectomy. RESULTS: Forty of 84 patients (47.6 %) had a Gleason score of ≥7, and 8 (9.5 %) had upstaged disease (≥pT3). Seven patients with upstaged disease also showed upgraded reclassification. Two patients with reclassification showed biochemical recurrence at 59 and 89 months after surgery, respectively. Preoperative parameters evaluated included age, PSA level, PSA density (PSAD), clinical T stage, and number and percentage of positive prostate cores. Among 82 patients with complete data, univariate analysis showed that PSAD (ng/ml(2)) was a significant parameter to discriminate patients with reclassified disease and those without reclassified disease (p < 0.001). Multivariate analysis revealed that PSAD was the only independent variable to predict disease with reclassification (p = 0.006). CONCLUSIONS: Preoperative PSAD may be a good indicator for selecting patients eligible for AS in the Japanese population.

Laparoscopic distal pancreatectomy for a pancreatic lymphoepithelial cyst: case report and review of literature.

CONTEXT: Lymphoepithelial cysts of the pancreas are a rare disease of true pancreatic cysts, the cause of which is unknown. The differential diagnosis is broad and includes many benign and malignant cystic lesions of the pancreas and surrounding organs. A combination of imaging modalities and fine needle aspiration might narrow the differential diagnosis. However, the final diagnosis can only be achieved with certainty after resection of the cyst. CASE REPORT: The present case report is a lymphoepithelial cyst of the pancreas that was resected laparoscopically. A 53-year-old man was incidentally found to have a cystic tumor in the tail of the pancreas after undergoing an abdominal ultrasound, which showed a 41x33 mm cystic mass in the pancreatic tail. He had no abdominal symptoms. Laparoscopic distal pancreatectomy and splenectomy were performed. Histologic examination revealed a lymphoepithelial cyst. CONCLUSION: Herein, we discuss the diagnostic difficulties and management decisions that face surgeons treating pancreatic cysts.

[A case of ring melanoma found while treating traumatic glaucoma].

BACKGROUND: Ring melanoma, a malignant melanoma which infiltrates over 180 degrees degrees of the ciliary body is very rare in Japan. We report a case of ring melanoma found while treating treatment of traumatic glaucoma with an ultrasound biomicroscope (UBM). CASE: A 44-year old woman presented with high intraocular pressure after blunt trauma in her left eye. CLINICAL FINDINGS: Best-corrected visual acuity OS was 1.2, and intraocular pressure was 30 mmHg. Gonioscopy showed about 180 degrees of the angle recession. Intraocular pressure was difficult to control in spite of anti-glaucoma drug treatment. Rapid progression of iris elevation and 360 degrees thickening of the ciliary body were detected by UBM. We detected atypical cells with melanine granules in the aqueous fluid and positive findings in PET-CT, leading to a diagnosis of ciliary body malignant melanoma. Consequently we enucleated the left eye. The histopathological diagnosis was ring melanoma. CONCLUSION: Ring melanoma is an important element in the differential diagnosis for untreatable secondary glaucoma.

The similarity of Type 1 autoimmune pancreatitis to pancreatic ductal adenocarcinoma with significant IgG4-positive plasma cell infiltration.

BACKGROUND: High serum immunoglobulin G4 (IgG4) levels and infiltration of IgG4-positive cells are characteristic of Type 1 autoimmune pancreatitis (AIP). We previously reported that increased regulatory T cells (Tregs) may regulate IgG4 production in AIP. Although an increased serum IgG4 concentration is observed in some patients with pancreatic ductal adenocarcinoma (PDA), clarification is still necessary. We have therefore studied the correlations between IgG4-positive cells and Tregs in patients with PDA. SUBJECTS AND METHODS: A total of 21 PDA and nine AIP patients were enrolled in our study. The numbers and ratios of Tregs, IgG4-positive, and IgG-positive cells immunohistochemically stained with anti-Foxp3, IgG4, and IgG antibodies, respectively, were counted in three areas of resected pancreata in PDA, peritumoral pancreatitis (PT), and obstructive pancreatitis (OP). RESULTS: In PDA, PT, OP area, the number of IgG4-Positive cells (5.183 ± 1.061, 2.250 ± 0.431, 4.033 ± 1.018, respectively; p < 0.05) and the ratio of IgG4/IgG (0.391 ± 0.045, 0.259 ± 0.054, 0.210 ± 0.048, respectively; p < 0.05) were significantly lower than those in AIP (21.667 ± 2.436 and 0.306 ± 0.052, respectively). The numbers of IgG4-positive cells did not differ significantly among the three areas of resected pancreata examined. However, the IgG4/IgG (0.391 ± 0.045) and Foxp3/monocyte (0.051 ± 0.008) ratios in PDA area were significantly (p < 0.05) higher than those in OP area (IgG4/IgG: 0.210 ± 0.048; oxp3/monocyte: 0.0332 ± 0.005), but not in PT area. Of the 21 cases of PDA, the ratio of IgG4/IgG was >40 % in nine (43%), six (29%) and three (14%) cases in PDA, PT and OP area, respectively. Foxp3 and IgG4 were positively correlated in OP area, but not in PDA and PT area. CONCLUSIONS: Clinicians should be careful when basing a differential diagnosis of PDA and AIP on the numbers of IgG4-positive cells and the ratio of IgG4/IgG, especially when determined using a small biopsied sample.

Utility of immunohistochemical analysis of KAI1, epithelial-specific antigen, and epithelial-related antigen for distinction of chromophobe renal cell carcinoma, an eosinophilic variant from renal oncocytoma.

Distinction of renal oncocytoma (RO) from chromophobe renal cell carcinoma (ChRCC) is important because their clinical behavior is different. As part of a search for the best available immunohistochemical markers to distinguish ChRCC from RO, we investigated the immunohistochemical profiles of these tumors. We selected 30 renal tumors consisting of ChRCC, typical variant (n = 14), ChRCC, eosinophilic variant (n = 6), and RO (n = 10). Their expression of cytokeratin (CK) 7, KAI1, epithelial-specific antigen (ESA), epithelial-related antigen (ERA), Claudin- 7, and Claudin-8 was studied using an autostainer. Immunoreactivity was assessed based on a combined score of the extent and intensity of staining. Compared to RO, a significantly higher percentage of the total ChRCCs stained positive for CK7 (85% vs. 10%, respectively), KAI1 (90% vs. 10%), ESA (95% vs. 10%), ERA (95% vs. 10%), and Claudin-7 (95% vs. 20%) (P < 0.001). Additionally, there was a significant difference between the percentage of ChRCC eosinophilic variant (ChRCC-E) and RO that stained positive for KAI1 (100% vs. 10%, respectively), ESA (83% vs. 10%), and ERA (83% vs. 10%) (P < 0.001). We recommend immunohistochemical analysis of KAI1, ESA, and ERA to distinguish ChRCC-E from RO.

Neo-adjuvant chemoradiation therapy using S-1 followed by surgical resection in patients with pancreatic cancer.

OBJECTIVE: The aim of this study was to compare short-term surgical results in pancreatic cancer patients who underwent surgical resection after neo-adjuvant chemoradiation therapy (NACRT) using S-1. METHODS: The study population comprised 77 patients with pancreatic cancer between 2006 and 2010. Out of 34 patients who underwent staging laparoscopy between 2008 and 2010, 31 patients without occult distant organ metastasis underwent chemoradiation and of whom 30 underwent pancreatectomy (NACRT group). Of the other 43 patients, 36 underwent surgical resection in 2006-2008, followed by adjuvant therapy (adjuvant group). The primary endpoint was frequency of pathological curative resection (R0). RESULTS: The new regimen of NACRT was feasible and safe. Twenty-eight of 30 (93%) patients in the NACRT group had R0 resection, which was significantly higher than in the adjuvant group (21 of 36 patients, 58%, p = 0.005). The number and extent of metastatic lymph nodes in the NACRT group (1 (0-25), N0/1; 18 of 38) was significantly lower than in the adjuvant group (2 (0-19), N0/1; 23 of 30), p = 0.0363). The frequency of intractable ascites in the NACRT group (eight of 30) was significantly higher than in the adjuvant group (two of 36, p = 0.035). CONCLUSION: Neo-adjuvant chemoradiation therapy using S-1 followed by pancreatectomy can improve the rate of pathologically curative resection and reduces the number and extent of lymph node metastasis.

Immunohistochemical application of S100A1 in renal oncocytoma, oncocytic papillary renal cell carcinoma, and two variants of chromophobe renal cell carcinoma.

S100A1 is a calcium-binding protein and a member of the S100 family. Recently, S100A1 immunohistochemistry may be an available marker in the differential diagnosis between renal oncocytoma and chromophobe renal cell carcinoma (RCC). However, there are no reports on S100A1 expression in oncocytic papillary RCC that has been recently identified. In this article, we immunohistochemically examined the expression of S100A1 protein in 18 renal tumors including 4 renal oncocytoma, 10 chromophobe RCCs, and 4 oncocytic papillary RCCs. All the cases of renal oncocytoma and oncocytic papillary RCC showed a positive reaction for S100A1 with cytoplasmic pattern. In chromophobe RCC, 3 of 4 tumors with typical variant and 4 of 6 tumors in eosinophilic variant were completely negative for S100A1. Finally, S100A1 immunohistochemistry may be useful in distinguishing renal oncocytoma from chromophobe RCC, but it may be of no use in the differential diagnosis between renal oncocytoma and oncocytic papillary RCC.

Prostate cancer detection by prebiopsy 3.0-Tesla magnetic resonance imaging.

OBJECTIVES: The diagnostic value of 3.0-Tesla magnetic resonance imaging (MRI) for prostate cancer remains to be determined. The aim of the present study was to assess the features of prostate cancer detectable by prebiopsy 3.0-Tesla MRI. METHODS: From January 2007 through to December 2008, 116 patients who were examined by prebiopsy 3.0-Tesla MRI underwent radical prostatectomy for localized prostate cancer. Prostate specimens were examined to see whether the largest cancer area was the same as the area indicated on the MRI. Univariate and multivariate logistic regression analyses were conducted to identify variables predictive of agreement between MRI and histopathological findings. RESULTS: Sixty-six (56.9%) patients were suspected of having prostate cancer on the basis of MRI findings. In 49 of these patients (74.2%), it was considered that there was agreement between the abnormal area on the MRI and the index tumor. Univariate analysis revealed that there were significant differences in abnormal digital rectal examination, capsular penetration, the diameter of the index tumor of the radical prostatectomy specimen, and the Gleason scores of the biopsy and radical prostatectomy specimens. Multivariate analysis revealed that the Gleason score of the radical prostatectomy specimen was associated with the accurate detection of the prostate cancer by MRI (P = 0.0177). CONCLUSIONS: In conclusion, 3.0-Tesla MRI tends to accurately diagnose prostate cancer with high tumor burden and aggressiveness. Multimodal examination (T2-weighted imaging, dynamic contrast-enhanced imaging, and diffusion-weighted imaging) is recommended for the diagnosis of prostate cancer using 3.0-Tesla MRI.

Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma: report of two cases.

Thyroid-like low-grade nasopharyngeal papillary adenocarcinoma (LGNPPA) is extremely rare; only four cases have been reported. Herein are presented the case reports of two Japanese male patients with thyroid-like LGNPPA. Macroscopically, these tumors were pedunculated polypoid masses on the roof of the nasopharynx. Microscopically, they were characterized by papillary and glandular epithelial proliferation. The papillae were complex and tightly packed with hyalinized fibrovascular cores and lined by columnar and pseudostratified cells with intervening spindle-shaped cells. Both cell types had round to oval vesicular nuclei with tiny nucleoli and mildly eosinophilic cytoplasm. Mitotic figures were not evident and necrosis was not observed. Psammoma bodies were seen focally in one of the patients. Transition from normal surface epithelium to tumor cells was identified in both cases. On immunohistochemistry the tumor cells were positive for cytokeratin (CK)7, CK19, thyroid transcription factor-1 (TTF-1) and vimentin. They were negative for CK5/6, CK20, thyroglobulin, S-100 protein and CD15. In situ hybridization for EBV was negative. Nasopharyngeal tumors with similar morphological appearance should be examined for TTF-1 immunoreactivity, and patients should be clinically followed to determine the course of this unusual disease and the significance of TTF-1 expression.

Renal carcinoid tumor: An immunohistochemical and molecular genetic study of four cases.

Few genetic studies of renal carcinoid tumor have been conducted thus far. We performed immunohistochemical and genetic examinations on four renal carcinoid tumors. Histologically, the tumors consisted of neoplastic cells with round to oval nuclei. Various growth patterns such as tightly packed cords and trabeculae, ribbon-like, trabecular, sheet-like or solid growth were observed. Nuclear chromatin showed a coarse and granular pattern. Immunohistochemically, tumors were positive for chromogranin A and synaptophysin. In the fluorescence in situ hybridization study, three of four tumors revealed monosomy of chromosome 3 (D3Z1), but one tumor showed monosomy of chromosome 13 (D13S319/13q34). Using PCR amplification and fragment analysis of three microsatellite markers (D3S1300, D3S666 and D3S1768) of chromosome arm 3p, one tumor showed loss of heterozygosity at D3S1300 and D3S1768, one tumor was not informative and the analysis of two tumors failed due to low DNA quality. In three cases, the VHL gene status was tested. Two tumors showed wild-type, but the analysis of one tumor failed to provide adequate results. In conclusion, we suggest that the abnormality of chromosome 3 is involved in the pathogenesis of renal carcinoid tumor.

A case of splenic low-grade mucinous cystadenocarcinoma resulting in pseudomyxoma peritonei.

Primary splenic mucinous cystadenocarcinoma (MCCa) is extremely rare, and only six cases appear to have been reported previously. We present herein a case of primary splenic MCCa resulting in pseudomyxoma peritonei (PMP). A 66-year-old Japanese woman presented to a hospital with a chief complaint of upper abdominal pain and a 7-year history of splenic cyst. Cyst rupture was noted on computed tomography, and splenectomy was performed. The abdominal cavity was filled with a large amount of gelatinous ascites, with the appearance of PMP. On the cut surface, multiple cysts containing mucinous material were found within and outside the spleen. Microscopically, splenic parenchyma was occupied by large mucinous pools focally lined with mucinous epithelial cells and mesothelial cell-like cells, which were considered benign. Outside the spleen, a low-grade MCCa component was found. No ectopic pancreatic or intestinal tissue was identified. Although most PMP cases are known to be caused by low-grade mucinous appendiceal tumor, the present case represents the first report of a splenic MCCa resulting in PMP.