We report a case of a 26-year-old type 1 diabetic woman presenting with acute lower abdominal pain, bloating, and vomiting. Initial examination revealed right lower quadrant tenderness and a suprapubic mass. Computed tomography (CT) imaging identified a 12-cm cystic structure suggestive of a dilated bowel loop with an adjacent inflamed 7-cm small bowel segment. Surgical exploration uncovered a Merkel\'s diverticulum-associated duplication cyst originating from the Meckel\'s diverticulum. Subsequent complications included an anastomotic leak, requiring relook laparotomy and the formation of a double-barrel stoma. The patient recovered and was discharged on day 13. This case highlights the diagnostic challenge of Meckel\'s diverticulum-associated duplication cysts, emphasizing the need for vigilance in managing complex abdominal presentations.

OBJECTIVE: TFE3-rearranged renal cell carcinomas (RCCs) harbor gene fusions between TFE3 and 1 of many partner genes. MED15::TFE3 fusion RCC is rare, often cystic, and easily misdiagnosed.
METHODS: This study aimed to characterize 2 cases of MED15::TFE3 fusion RCC with extensive cystic change using fluorescence in situ hybridization and targeted RNA sequencing.
RESULTS: Both patients were young adult women aged 29 and 35 years. Radiologically, both presented with a cystic Bosniak category II renal lesion. The cysts measured 9.3 cm and 4.8 cm in greatest dimension. Both patients underwent cyst enucleation, and neither had tumor recurrence or metastasis at 26 and 6 months of follow-up, respectively. Microscopically, both tumors were entirely cystic, with thick, fibrous cystic walls lined by small clusters of cells with clear to eosinophilic cytoplasm and uniform, round nuclei with inconspicuous nucleoli. There were also small aggregations of similar clear cells within the cystic walls. Foci of basement membrane-like material depositions were noted in 1 case; calcifications were observed in both cases. Both cases demonstrated nuclear positivity for PAX8 and TFE3 and cytoplasmic staining for Melan-A; HMB45, CAIX, and CK7 were negative. Fluorescence in situ hybridization revealed that both tumors were positive for TFE3 rearrangements. RNA sequencing identified MED15::TFE3 gene fusions in both cases.
CONCLUSIONS: The main differential diagnosis of MED15::TFE3 fusion RCC includes multilocular cystic renal neoplasm of low malignant potential and atypical renal cysts. Molecular confirmation of TFE3 fusion is essential for establishing the correct diagnosis.

Presented are four cystic renal masses which harbored a MED15::TFE3 gene fusion detected by RNAseq, mimicking multilocular cystic neoplasm of low malignant potential. Clinicopathologic and outcomes data were collected for all cases. Radiologically, three cases were diagnosed as complex cystic masses and one case as a renal cyst, three years prior to surgery. The tumors ranged in size from 1.8 to 14.5 cm. Grossly, all masses were extensively cystic. Microscopically, cells with a clear or minimally granular cytoplasm and nuclei with inconspicuous nucleoli lined the cysts\' septa. Focally, small mass-forming aggregates of malignant cells were present between septae and were associated with psammomatous calcifications. In case one, apparent prior cyst wall rupture was associated with reactive changes and cystic spaces filled with fibrin clots. Two of the tumors were staged as T1a, one as T1b, and the other as T2b. By immunohistochemistry, the tumors were positive for TFE3, MelanA, and P504S, with apical CD10 while CAIX and CK7 were negative. RNA sequencing was performed on all cases revealing a MED15::TFE3 gene fusion. The patients were alive and without evidence of disease 11-49 months (mean 29.5) after partial nephrectomy. To date, 12 of the 15 MED15::TFE3 fusion renal cell carcinomas published in the literature are cystic, with three being extensively cystic. Thus, if a multilocular cystic renal neoplasm is encountered in a kidney specimen, translocation renal cell carcinoma should be included in the differential diagnosis as cystic MED15::TFE3 tRCCs carry an uncertain prognosis making recognition for future characterization necessary.

As the majority of incidentally detected lesions in the anterior mediastinum is small nodules with soft tissue appearance, the differential diagnosis has typically included thymic neoplasm and prevascular lymph node, with benign cyst. Overestimation or misinterpretation of these lesions can lead to unnecessary surgery for ultimately benign conditions. nonsurgical anterior mediastinal lesions. The pitfalls of MRI evaluation for anterior mediastinal cystic lesions are as follows: first, we acknowledge the limitation of T2-weighted images for evaluating benign cystic lesions. Due to variable contents within benign cystic lesions, such as hemorrhage, T2 signal intensity may be variable. Second, owing to extensive necrosis and cystic changes, the T2 shine-through effect may be seen on diffusion-weighted images (DWI), and small solid portions might be missed on enhanced images. Therefore, both enhancement and DWI with apparent diffusion coefficient values should be considered. An algorithm will be suggested for the diagnostic evaluation of anterior mediastinal cystic lesions, and finally, a management strategy based on MRI features will be suggested.

The existence of a cystic mass which walls originated from a metastatic gallbladder adenocarcinoma is infrequent. We present the case of 68-year-old male that present to the emergency department with abdominal distention, hyporexia and jaundice. Upon exploratory laparotomy, a duodeno-colonic cyst with walls formed by metastatic cells derived from a Gallbladder Adenocarcinoma. Metastatic disease from a gallbladder adenocarcinoma to transverse colon and duodenum formed adherences between both organs, leading to the formation of cystic mass. Cancer cells have multiple adaptation mechanisms in order to survive harsh environments.
La existencia de un quiste cuyas paredes se originaron de una metástasis de adenocarcinoma de vesícula biliar es infrecuente. Varón de 68 años con distensión abdominal, hiporexia e ictericia. En la laparotomía exploratoria se evidencia un quiste duodeno-colónico de paredes conformadas por células metastásicas producto de un adenocarcinoma de vesícula biliar. La metástasis del adenocarcinoma de vesícula biliar hacia colon transverso y duodeno formaron adherencias entre ambos órganos, conduciendo a la formación de una masa quística. Las células cancerígenas pueden adaptarse de muchas maneras para sobrevivir en entornos adversos.

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UNASSIGNED: Myxoma is a benign tumor and is mesenchymal in origin. Myxomas of the retroperitoneum are extremely rare entities.
METHODS: We here report a case of a 67-year-old male who presented with progressive abdominal distention for 3 years. Laboratory investigations revealed a reduction in erythrocytes, lymphocytes, hemoglobin, and an elevation in carbohydrate antigen 19-9. Imaging findings showed a multilocular cystic mass in the right abdomen with thin septa and internal calcifications. Laparotomy revealed that the mass had arisen from the retroperitoneum and the histological study suggested the diagnosis of myxoma.
CONCLUSIONS: Myxoma features as a \"cystic mass\" in imaging studies. Therefore, the possibility of a cystic lymphangioma, cystic mesothelioma and myxoma should be considered when a multicystic lesion in the retroperitoneal space is observed. Due to the rarity of retroperitoneal myxomas and lack of specific manifestations and diagnostic methods, preoperative diagnosis is often delayed or incorrect. And until now, only a few cases of retroperitoneal myxoma have been reported.
CONCLUSIONS: The report will increase the understanding of the diagnosis and treatment of retroperitoneal myxomas. A brief review of the related literature was also carried out.

Third branchial cleft cyst is a rare congenital disease of the neck. It presents as a painless mass that develops rapidly in the neck following an infection. This is the first case report of recurrent laryngeal nerve palsy caused by a third branchial cleft cyst. A 30-year-old woman presented with a 3-month history of hoarseness as her only symptom; she had no pain, fever, dysphagia, dyspnoea, or palpable neck mass. Laryngoscopy revealed that her right vocal cord was paralyzed. Computed tomography and magnetic resonance imaging revealed a cystic mass in the right tracheoesophageal groove that was closely associated with the trachea. Intraoperatively, the cyst was found not to originate from the thyroid or trachea, but it was compressing the right recurrent laryngeal nerve. The hoarseness resolved the day after the cyst was removed.

UNASSIGNED: Ventricular cystic masses are uncommon. Elucidating the cause is essential for early directed therapy and prevention of complications. We present two cases of ventricular cystic masses, one in each ventricle, after myocardial infarction (MI) and ventricular septal rupture (VSR), respectively.
UNASSIGNED: Patient 1 is a 58-year-old male with left brachio-facial stroke and evolved anterior MI. A left ventricular (LV) cystic thrombus was seen on transthoracic echocardiogram (TTE) and cardiac magnetic resonance (CMR) imaging. He was started on anticoagulation with reduction in thrombus size 11 days later. Patient 2 is a 67-year-old male with evolved anterior MI, severe LV systolic dysfunction, and normal right ventricular (RV) function. He was readmitted two weeks later with fever, heart failure, Streptococcus agalactiae bacteraemia, and septic pulmonary emboli. Transthoracic echocardiogram showed biventricular systolic dysfunction and a RV cystic mass associated with a partial VSR. He was treated with anticoagulation and antibiotics. Repeat TTE 5 weeks later revealed near resolution of the cystic mass and complete VSR. Cardiac magnetic resonance confirmed these findings and also showed a localized mid-septal transmural infarction at the VSR site. He underwent percutaneous coronary intervention to the left anterior descending and circumflex arteries, and percutaneous VSR closure with a muscular ventricular septal defect device later.
UNASSIGNED: Our two cases demonstrate that ventricular thrombi can present as cystic masses after MI and VSRs. Infectious, vascular, or oncogenic causes should be considered in the appropriate clinical context. Early diagnosis and treatment is essential to prevent embolic complications, and secondary infection.