Advances in drug therapy for hepatocellular carcinoma are remarkable, and currently eight drug therapy regimens are covered by insurance. At the same time, drug therapy is introduced depending on the stage of hepatocellular carcinoma, where the purpose of each drug therapy must be clarified : adjuvant for resectable, neoadjuvant for borderline resectable, and conversion for unresectable malignancies. With combination of surgery and drug therapy based on the well understanding of drug characteristics, we can expect further improvement of therapeutic outcomes. For that purpose, it is challenging but necessary to clearly define the resectability classification, and to clarify the treatment strategy for hepatocellular carcinoma through an all-Japan prospective clinical trial.

Closure of the temporary stoma after low rectal resection is generally considered after 3 months. However, stoma-related complications have become a problem, and there are reports of early stoma closure mainly in foreign countries. We reviewed 10 cases of early stoma closure after rectal resection experienced in our department. The median age was 62 years old, and there were four men and six women. Their diseases included adenocarcinoma in eight cases and neuroendocrine tumor (NET) in two cases, and the median distance from the anal verge to the tumor was 70 mm. Gastrografin enema was performed before closure to confirm that there were no problems with the rectal anastomosis. The median distance from the anal verge to the anastomosis was 35 mm, and the median period from resection to closure was 12.5 days. No complications related to rectal anastomosis were observed, and the median length of hospital stay after resection was 21 days in eight patients who underwent resection and closure in the same hospitalization. Early stoma closure has the advantage of stoma creation to prevent aggravation of anastomotic leakage while also avoiding stoma-related complications as much as possible.

A 37-year-old male patient presented to our hospital with complaints of a right breast mass. On palpation, an elastic mass approximately 2 cm × 1 cm in size, slightly caudal to the right nipple, was detected. Mammography revealed asymmetrical breast tissue below the right nipple. Ultrasonography showed a 1.2 × 1.1 × 0.6 cm hypoechoic mass below the right nipple with abundant blood flow in the surrounding area and increased elasticity. The patient had a family history of breast cancer, with his mother surviving it at 68 years of age, and his sister dying of it at 26 years of age. An ultrasound-guided core needle biopsy was performed on the same day, and a diagnosis of chronic mastitis with no evidence of malignancy was made. We encountered a case in which gynecomastia was suspected based on initial clinical findings, but the diagnosis was chronic mastitis based on biopsy results. In this report, we provide a literature review on this topic.

Metaplastic breast carcinoma is a rare disease, categorized as a special type, and accounts for <1% of all breast cancer cases. Herein, we report a case of metaplastic breast carcinoma in a male patient. A 73-year-old man presented with a growing mass in his right breast and was diagnosed with adenomyoepithelioma suspicious for malignant transformation, and underwent total mastectomy of the right breast. The pathological diagnosis was triple-negative metaplastic breast carcinoma, pStage IIA. He achieved a relapse-free survival of 3 years 8 months.

A 70-year-old woman with a pacemaker (PM) implanted in her left anterior chest four years previously noticed a mass in her left axilla and visited our hospital. A growth with a diameter of 6 cm, centered in the E region of the left breast, was detected, and enlarged lymph nodes were identified in the left axilla. A biopsy revealed an invasive ductal carcinoma. However, lymph node metastasis was also discovered in the left supraclavicular region, leading to a locally advanced breast cancer diagnosis. Preoperative chemotherapy was performed so that cancer in her left breast, including the left supraclavicular lymph node, shrank and was rendered operable. Postoperative radiotherapy was indicated, and a leadless PM was implanted preoperatively. A calcified lesion was also found in her right breast, and the biopsy diagnosis confirmed noninvasive ductal carcinoma. Bilateral mastectomy, left axillary lymph node dissection, and right sentinel lymph node biopsy were performed. The patient underwent a total left mastectomy followed by radiotherapy (50 Gy/25 Fr) as scheduled, without recurrence, for four years after surgery. With the aging of the population, the number of PM implantation cases is increasing. Careful diagnosis and treatment are required when breast cancer occurs at the site of PM implantation.

The patient is a 65-year-old woman diagnosed with right breast cancer, cT4bN1M0 Stage IIIB (invasive ductal carcinoma, ER 50%, PgR 20%, HER2 3+). Contrast-enhanced magnetic resonance imaging of the breast showed hypoplasia of the right pectoralis major and absence of the right pectoralis minor. Hypoplasia of the right fingers led to the diagnosis of Poland's syndrome. The patient received preoperative chemotherapy with endocrine therapy and underwent right mastectomy and axillary node dissection. Postoperatively, the patient received endocrine therapy, molecular-targeted drug therapy, and radiotherapy. Three years and eight months after the operation, the patient is alive without cancer recurrence. We should pay attention to the operation of the breast cancer in patients with Poland syndrome because the unique anatomy of this condition can easily lead to misidentification of blood vessels and nerves.

Here, together with a literature review, we report on a case of breast cancer with extensive infarct necrosis and fistula formation, which was difficult to diagnose and treat preoperatively. A 42-year-old woman visited our hospital complaining of a painful, rapidly enlarging growth in her left breast. During the examination, a 10 × 15 cm mass in her left breast and left axillary lymph node were palpated, and a fistula was detected at the 12 o'clock position. Breast ultrasonography and contrast-enhanced MRI revealed an approximately 10 cm mass with a mixture of liquid and solid components in the left breast and an abnormal communication to the skin. The pathological findings of the initial needle biopsy led to a diagnosis of ductal hyperplasia. However, on re-examination, an invasive ductal carcinoma was identified. As T4 breast cancer with axillary lymph node metastasis was considered, she underwent a total left mastectomy, axillary lymph node dissection, and full-thickness skin grafting. Postoperative histopathological examination yielded a diagnosis of encapsulated papillary carcinoma with invasive components (mucinous). Extensive infarct necrotic tissue was observed in the encapsulated papillary carcinoma without tumor invasion in the skin surrounding the fistula.

A 47-year-old woman presented to our hospital with a left breast mass and was diagnosed with left breast cancer using a core needle biopsy (CNB). The day after the biopsy, redness and pain at the puncture site were observed, and the patient was treated with antibiotics and drainage, with the assumption that it was a wound infection ; however, no improvement was observed. Each imaging examination showed a continuous soft-tissue shadow between the tumor and the epidermis of the biopsy puncture site. An incisional tissue biopsy was performed at the same site, and malignant findings were obtained. The tumor was aggravated by severe inflammation and was resistant to chemotherapy and radiotherapy, and the patient died 176 days after the initial diagnosis. The patient did not reach the downstaging because the time required to diagnose the symptoms immediately after CNB delayed the start of chemotherapy due to the rapid progression of tumor cells and inflammatory spread. Although there have been numerous reports of needle tract seeding after CNB, there have been no reports such as the present case in which rapid progression with clinical findings was observed on imaging. This case involved inflammatory spillover of the tumor by a mechanism other than conventional needle tract seeding as the cause of tumor aggravation.

Lobular carcinoma in situ (LCIS) or breast cancer coexisting with a phyllodes tumor is rare. Here, we report a case of a phyllodes tumor coexisting with LCIS. A 47-year-old woman became aware of a right breast mass in January 2020. She underwent core needle biopsy and was diagnosed with LCIS at a different hospital. At the time of her first visit to our hospital, a 100-mm mass was palpated in her right breast. Mammography revealed a well-defined smooth mass occupying the entire right breast. Ultrasound examination also showed an oval 120-mm mass with smooth borders, isoechoic internal heterogeneity, and an increased back-echo level in the right breast. Core needle biopsy revealed a phyllodes tumor coexisting with LCIS. A right mastectomy and sentinel node biopsy were performed. Pathological examination revealed a benign phyllodes tumor with LCIS in the epithelial component of the mass. Neither LCIS nor breast cancer lesions were found outside of the phyllodes tumor.

There are few reports on robot-assisted simultaneous resection of combined bronchogenic cyst and extrapulmonary sequestration that is a rare condition. A 15-year-old girl who was detected having an abnormal shadow in a chest radiograph at physical examination was referred to our hospital for further examinations and treatments. Chest CT scan and MRI study showed a well-defined, homogeneous posterior mediastinal mass and an atelectasis-like soft tissue shadow caudally adjacent to the posterior mediastinal mass. Contrast-enhanced CT scan showed an anomalous artery flowing from the descending thoracic aorta into this atelectatic pulmonary lobe-like structure bordering the caudal side of a posterior mediastinal mass, therefore we could lead to a diagnosis of extrapulmonary sequestration. We performed robot-assisted simultaneous resection of the posterior mediastinal tumor and extrapulmonary sequestration. The posterior mediastinal mass was resected first, and subsequently extrapulmonary sequestration was resected at the stalk containing the anomalous artery using an automatic suture via robot-assisted thoracoscopic surgery. The patient had a good postoperative course and was discharged on the third postoperative day. The pathological diagnosis of the posterior mediastinal tumor was bronchogenic cyst. Robot-assisted thoracoscopic surgery is a very useful procedure for resection of both mediastinal tumor and pulmonary sequestration. We report this case with some bibliographical comments.

A 20-year-old woman presented with left anterior chest pain and fever. A chest radiograph revealed a bulge impacting the left hilar region. A chest computed tomography revealed an anterior mediastinal tumor and pneumonia in the upper lobe of the left lung. After undergoing antibiotic treatment for pneumonia, the patient underwent robot-assisted thoracoscopic surgery via a subxiphoid approach for resection of the anterior mediastinal tumor and partial resection of her left upper lobe. A histological examination revealed a mature teratoma that had penetrated the upper lobe of the left lung. We used robot-assisted thoracoscopic surgery to perform a complete resection of the mature mediastinal teratoma penetrating the left lung. She was discharged on the third postoperative day without any complications. Even in cases where a mediastinal tumor has penetrated, depending on the case, it is suggested that the operation can be completed under the endoscope due to the multi-joint and precise operability of the robot.

Congenital cystic adenomatoid malformation (CCAM) is a congenital cystic disease that is believed to occur as a result of airway obstruction during bronchogenesis and bronchiogenesis in the embryonic period. Since approximately 80% of CCAM cases are usually detected at less than one year of age, detection in adults is rare, and there have been few cases reported in Japan. We report two cases of CCAM with different imaging findings that were treated surgically in our hospital.

A 48-year-old man presented to our hospital with a 2.9-cm suspected lung cancer in S9/S10 of the right lung. We scheduled right lower lobectomy and lymphadenectomy (ND2a-1). The intraoperative pathological examination showed that the nodule was adenocarcinoma, and it was removed by right lower lobectomy under robot assistance. During the surgery, we selected the EndoWrist^® Stapler 45 Green for stapling the right lower lobe bronchus. We found air leakage from the bronchial stump after the inflation to the right lung at 20cmH₂O because of stapling failure. We closed the leak site of the bronchial stump with sutures supported by pericardial fat pledgets under robot assistance. Although it is reported that adverse events related to stapling occurred in approximately 1.6% of all cases, there have been no minute reports on stapling failure due to the use of da Vinci stapler. The stapler used in the procedure is likely inappropriate for young males who have thick bronchial walls. Depending on each case, the additional use of the stapler for thoracoscopy should be considered.

Oral use of albendazole (ABZ) is recommended for pulmonary metastasis of echinococcosis. We have surgically treated a case of the disease presented with recurrent bouts of bloody phlegm. The patient was a man in sixty-four and had undergone hepatic resection for hepatic echinococcosis with multiple pulmonary metastases. After the surgery, he had been treated with oral ABZ while bloody phlegm developed twice, 3 years and 5 years after the initiation of the ABZ therapy, respectively. These hemorrhages were likely to arise from the metastatic lesion at the S1 of the right lung. We performed thoracoscopic partial resection of the same pulmonary site. After the operation, bloody phlegm improved. As of one year and two months after the operation, sustained oral administration of ABZ leads to uneventful postoperative course ; without increasing the number of pulmonary metastatic lesions, without enlarging the remnant pulmonary metastatic lesions, and without having recurrence of hepatic metastatic lesions. In the treatment of echinococcosis associated with multiple pulmonary metastases, some patients can have recurrent bouts of respiratory symptoms such as bloody phlegm even though they have been on ABZ oral therapy. There is room for consideration of local partial resection of causative lesion as a therapeutic option.

A 59-year-old woman was referred to the emergency department because of traffic trauma. She was diagnosed with a traumatic left diaphragmatic hernia complicated by pericardial rupture. Laparotomy revealed a traumatic diaphragmatic defect measuring 120 mm in diameter and pericardial injury. We repaired the diaphragmatic defect and pericardial injury with continuous primary sutures. The occurrence of traumatic diaphragmatic hernias complicated by pericardial injury is rare. Anatomically, the diaphragm and pericardium are continuous tissues. In this case, we considered that the external force applied to the diaphragm continued to spread to the pericardium. Traumatic diaphragmatic injury is often associated with multiple organ injuries, and pericardial injury should be recognized as one of them.

Although we come across clinical reports of gastrointestinal stromal tumor (GIST) of the stomach with calcification, there are few reports of gastric GIST with ossified components. We report a case of gastric GIST with severe calcification and partial ossification. A 77-year-old woman was pointed out to have an upper abdominal abnormal shadow in a chest X-ray examination at a medical checkup, and a CT scan revealed a heavily calcified mass in the lesser curvature of the stomach. The tumor was resected by laparoscopic local resection. The pathological diagnosis was GIST with severe calcification and partial osseous degeneration. The mechanism of calcification or ossification within GIST has not been clearly elucidated, nor has the clinical prognosis been established. We present a case of gastric GIST with severe calcification and partial ossification.

A 46-year-old woman was referred to our hospital for a detailed examination of a mass with tenderness in the right lower abdomen. Contrast-enhanced computed tomography of the abdomen showed a 4-cm mass with multiple calcified stones and fluid in the pelvic cavity. The mass was in contact with the terminal ileum and was diagnosed as a Meckel's diverticulum with enteroliths. Blood tests showed no inflammatory reaction, but the patient was symptomatic, so elective laparoscopic resection of the Meckel's diverticulum was performed. Postoperative histopathological examination showed Meckel's diverticulum with ectopic gastric mucosa, and about 20 enteroliths in the diverticulum were 0.5-2 cm in size, including sharp ones. Postoperatively, the abdominal pain resolved. Although Meckel's diverticulum may necessitate emergency surgery due to complications such as diverticulitis or perforation, asymptomatic Meckel's diverticulum does not require treatment, and there have been few cases of elective surgery reported. Although Meckel's diverticulum with enteroliths is rare, if enteroliths are thought to cause chronic abdominal pain, diverticulitis, or perforation, elective surgery should be considered.

Acute appendicitis is the most common cause of acute abdomen in pregnant women. Although laparoscopic appendectomy is commonly performed, reports of its use are limited. Seven cases of laparoscopic appendectomy for acute appendicitis during pregnancy were seen from March 2017 to July 2022. By trimester at the onset of the disease, 3 were in the first trimester (up to 15 weeks' gestation), 3 were in the second trimester (from 16 to 27 weeks' gestation), and 1 was in the last trimester (from 28 weeks' gestation). Port placement was determined according to gestational week. All operations were completed safely without any complications, including two cases of single-incision laparoscopic appendectomy (SILS). In laparoscopic surgery, it is essential to avoid interference of the forceps with the uterus. The optimal port placement for laparoscopic appendicectomy by gestational week is described.

An 80-year-old man was diagnosed with sigmoid colon cancer (cT4bN0M0, cStage IIc) with bladder invasion and underwent open sigmoid colectomy and partial cystectomy. The histopathological diagnosis was moderately differentiated adenocarcinoma (pT4bN0M0, pStage IIc) with tumor invasion of the muscle layer of the bladder, but the bladder resection margin was negative. Computed tomography (CT) 6 months after surgery showed a 5-mm mass lesion on the wall of the bladder, and transurethral resection of bladder tumor (TUR-Bt) was performed. Histopathological investigations showed that this was adenocarcinoma resembling the sigmoid colon cancer, and intravesical recurrence of sigmoid colon cancer was diagnosed. The resection margin was negative, but CT 9 months after the original surgery showed that there was another 30-mm mass lesion in a part of the bladder distant from the resected lesion. TUR-Bt was again performed, but muscle layer invasion was suspected, and simple total cystectomy and bilateral cutaneous ureterostomy were performed. Histopathological investigations showed metastatic adenocarcinoma and dissemination in the bladder, and recurrence due to dissemination in the remaining bladder was suspected.

The patient was a 68-year-old man who underwent laparoscopic low anterior resection of the rectum for Ra rectal cancer. The pathological diagnosis was pT3 (SS) N2aM0 pStage IIIb. His postoperative course was uneventful, and oral ingestion was started on the 6^th postoperative day (POD). On the 14^th POD, all drains were removed. On the next day, he developed high fever and pneumaturia. Close examination clarified a seminal vesicle-rectal fistula. Management with fasting and high-caloric infusion was started, and on the 65^th POD, we could confirm the seminal vesicle-rectal fistula to have closed. Seminal vesicle-rectal fistula is a relatively rare complication after rectal resection. Due to its rarity and successful conservative therapy that we used, we present the case, together with a review of the literature.

The patient was a 48-year-old woman. She visited her previous physician with a chief complaint of right hypochondralgia, her abdominal ultrasonography showed a 40-mm tumor in liver S5, and she was referred to our department. Blood tests showed no particular abnormalities, but dynamic computed tomography and EOB-MRI showed that the tumor was heavily stained in the early phase and washed out in the late phase. Hepatocellular carcinoma was diagnosed, and laparoscopic S5 partial resection of the liver was performed. Histopathological examination showed large, polygonal tumor cells with eosinophilic reticulum, bright nuclear chromatin, and distinct nucleoli that had proliferated diffusely with alveolar to cord-like structures. Smooth muscle-like eosinophilic spindle-shaped tumor cells were also present in some areas. Immunostaining was positive for myogenin, vimentin, HMB-45, SMA, and CD68. Based on these findings, the patient was diagnosed with primary perivascular epithelioid tumor of the liver. Primary perivascular epithelioid cell tumor of the liver is a very rare disease. A case of primary perivascular epithelioid cell tumor of the liver that was laparoscopically resected is presented.

A case of hepatocellular carcinoma (HCC) with bile duct invasion and contralateral multiple nodules successfully treated by conversion hepatectomy after atezolizumab plus bevacizumab treatment is reported. An 81-year-old man with liver tumors and a dilated intrahepatic bile duct in the left lobe was referred to a hospital. A 60-mm HCC in segment 4 with infiltration to the left intrahepatic bile duct and three small HCCs in segments 5, 7, and 8 were seen on computed tomography (CT). He was diagnosed with Stage IVa HCC and treated with atezolizumab plus bevacizumab. After 10 courses of treatment, the tumor marker levels decreased, the tumors in segments 4 and 7 had shrunk markedly, and the tumors in segments 5 and 8 had disappeared. However, contrast-enhanced CT showed a viable lesion in the tumor, and he was referred to our hospital for surgery. A decision was made to perform conversion surgery, and the tumor was completely removed by left hemihepatectomy. Histopathologically, complete response to atezolizumab plus bevacizumab treatment was confirmed. The criteria for conversion surgery in unresectable HCC remain unclear. The indications and optimal timing of conversion surgery after atezolizumab plus bevacizumab treatment are considered.

A 58-year-old man presented to a hospital with general fatigue and lower leg edema. He was referred to our hospital because of anemia and a gallbladder tumor. As a result of close examination, he was diagnosed as having gallbladder bleeding associated with gallbladder cancer (Gf, papillary-expanding type, hep, 50×40mm, cT2b, cPV0, cA0, cN0, cM0, Stage II B). In addition, endoscopic retrograde cholangiopancreatography (ERCP) performed preoperatively revealed association of pancreaticobiliary maljunction without bile duct dilatation, and duplication of the common bile duct which is a rare morphological abnormality. Extended cholecystectomy and lymphadenectomy were performed. This patient has been alive as of 24 months after surgery without any signs of recurrence. Duplicated bile ducts are extremely rare congenital malformations of the biliary tract, defined as “congenital anomalies in which two patent bile ducts open separately into the gastrointestinal tract.”. Only a few dozen cases have been reported in the past. We report a rare case of gallbladder cancer with duplication of the bile duct and pancreaticobiliary maljunction without bile duct dilatation, which presented with gallbladder bleeding.

Case : In a 61-year-old man hospitalized for acute aortic dissection (Stanford type B), a follow-up computed tomography scan showed an aneurysm in the pancreatoduodenal artery and surrounding blood speculum formation. Median arcuate ligament syndrome was observed, and dissection was seen from near the origin of the celiac artery to the superior mesenteric artery, but the origin of the superior mesenteric artery was intact. After preparing for emergency laparotomy, a decision was made to perform arterial embolization. A micro-catheter was inserted through the superior mesenteric artery, and the posterior superior pancreaticoduodenal artery and the posterior inferior pancreaticoduodenal artery were coil embolized. No bleeding or worsening of dissection was observed. Although transiently decreased peristalsis of the upper gastrointestinal tract was observed postoperatively, the patient was discharged from the hospital on the 14th postoperative day.

Arterial embolization, stenting, and laparotomy are treatment options for ruptured pancreaticoduodenal aneurysms, and arterial embolization is minimally invasive and has relatively better outcomes than other treatments. In the present case with severe intravascular disease, arterial embolization with a backup system involving multiple departments was considered useful.

An 80-year-old man was suspected to have lymphoproliferative disease because of splenomegaly and enlarged lymph nodes throughout the body shown by enhanced computed tomography (CT). Positron emission tomography-CT, lymph node biopsy, and skin biopsy were performed, but no definitive diagnosis was made. Therefore, splenectomy was required. CT showed the tail of the pancreas very close to the splenic hilum and left-sided portal hypertension. Therefore, manipulation of the splenic hilum was considered to require extreme caution. To avoid intraoperative and postoperative complications, selective splenic artery branch embolization was performed immediately before laparoscopic partial splenectomy. The patient was discharged on postoperative day 5 without any complications and underwent chemotherapy for the pathological diagnosis of angioimmunoblastic T-cell lymphoma. Laparoscopic partial splenectomy combined with selective splenic artery embolization has not yet been reported, but it was useful and safe in the present case.

A 65-year-old man tested positive for fecal occult blood in a routine health checkup. Lower gastrointestinal endoscopy showed a 10-mm Ip polyp in the sigmoid colon and a 12-mm Is polyp in the rectum, and endoscopic mucosal dissection was performed. The histopathological diagnosis was adenocarcinoma, tub1>por2, pT1a, Ly1a, V0 for the sigmoid colon lesion and adenocarcinoma, tub1>por2, pT1b (1,750μm), Ly1a, V1a for the rectal lesion, and laparoscopic low anterior resection was performed as an additional procedure. Although there had been no sign of obvious lymph node enlargement on preoperative and intraoperative findings, 4 of the 12 pararectal lymph nodes in the resected specimen showed metastases of poorly differentiated adenocarcinoma. Immunohistostaining results were negative for CK7, CK20, and CDX2, but positive for prostate-specific antigen (PSA), and lymph node metastases of prostate cancer were therefore suspected. Additional tests showed an elevated serum PSA level, and a hypointense mass in both lobes of the prostate was seen on T2-weighted imaging of magnetic resonance imaging. Biopsy confirmed the presence of adenocarcinoma, and prostate cancer was therefore diagnosed. There have been few reports of pararectal lymph node metastases of prostate cancer, and this case in which prostate cancer was diagnosed by the identification of pararectal lymph node metastases in a patient being treated for colorectal cancer is reported, along with a short discussion of the literature.

A 52-year-old woman consulted a physician at the Department of Cardiology in our hospital because she had hypertension of over 180 mmHg. To rule out primary aldosteronism, abdominal computed tomography (CT) was performed, revealing a 30 × 40 mm tumor with calcification, surrounded by the duodenum and right kidney. Enhanced CT displayed pale tumor staining at the equilibrium phase. Fluorodeoxyglucose-positron emission tomography (FDG-PET) /CT showed accumulation of SUVmax 3.5 in the same area, and magnetic resonance imaging (MRI) showed a homogeneous tumor with low T1W1 and markedly high T2W1 signals. Overall, this tumor was diagnosed as either a neurogenic tumor, a liposarcoma, or a hemangiosarcoma. Finally, we decided on tumor resection to make a definitive diagnosis without a preoperative needle biopsy. The operation was initiated via an anterior approach through the abdominal cavity. The resected tumor was diagnosed as a cavernous hemangioma. Retroperitoneal cavernous hemangiomas are quite rare. Perioperative diagnosis is usually difficult because the findings from images, including enhanced CT and MRI, display great diversity, such as hypo- or hypervascular staining. In conclusion, we should consider cavernous hemangioma as a differential diagnosis in retroperitoneal tumors.

A 62-year-old man was referred to our hospital because an abdominal ultrasonography examination indicated a tumor on the dorsal side of his pancreas. Computed tomography and magnetic resonance imaging showed a clear border between the tumor and the pancreas. Endoscopic ultrasonography (EUS) revealed a 23-mm hypoechoic mass on the dorsal side of the pancreatic body and connected to the splenic artery. It was diagnosed as a neuroendocrine tumor by EUS-fine-needle aspiration (FNA), and the patient underwent laparoscopic tumor resection. Intraoperative findings showed no continuity between the pancreas and the tumor. The pathological diagnosis was NET-G2, and there was no evidence of origin from the pancreas, lymph nodes, adrenal gland, or ganglia, suggesting a retroperitoneal primary. No evidence of recurrence was observed 2 years after the surgery. We experienced a case of a primary retroperitoneal neuroendocrine tumor arising on the dorsal side of the pancreatic body and could be resected laparoscopically.

Endometriosis may occur in any organ of the body, but its emergence in the retroperitoneal cavity is infrequent and canceration is rare. We report a retroperitoneal tumor with a histological picture suggestive of malignant transformation due to endometriosis. A 42-year-old woman, gravida 1 para 1, visited our hospital complaining of right, upper-quadrant pain during menstruation. An abdominal computed tomography (CT) scan revealed the presence of a retroperitoneal tumor. Magnetic resonance imaging showed a cystic mass measuring 10 × 9 cm with liquid and solid components on the dorso-lateral surface of the ascending colon. Her CA19-9 levels had increased to 2,120 U/mL and CA-125 levels increased to 116 U/mL. A retroperitoneal tumor resection was performed without invasion into the other organs. Pathological findings revealed a cystic lesion with a brownish-red fluid. This lesion was identified as an adenocarcioma, histologically similar to a gynecological carcinoma. The lesion was, therefore, comprehensively determined to be a retroperitoneal malignant tumor associated with endometriosis. A positron emission tomography-CT scan showed no obvious accumulation and a total hysterectomy, bilateral adnexectomy, and partial omentectomy were additionally performed for diagnosis ; however, no pathologically malignant findings were observed. The patient underwent six courses of TC therapy postoperatively for endometrial cancer and is currently under observation without any recurrence.