Solitary fibrous tumors are rare mesenchymal neoplasms that can range from slow-growing to aggressive tumors. This report presents a unique case of a young male patient with a solitary fibrous tumor involving the seminal vesicle, a rare location, and reinforces incidental discovery of these tumors on imaging and physical exams. Detection of these tumors is imperative to identify and treat malignancy. In our case, a 39-year-old previously healthy Asian male presents to the emergency department as a trauma admission post bicycle crash and is incidentally found to have a pelvic mass on computed tomography imaging of the pelvis. The patient underwent trans-anal biopsy which showed spindle epithelioid cells positive for CD34 and STAT6 markers, with a morphological and immunohistochemical profile consistent with a solitary fibrous tumor. The patient underwent surgery with a robotic-assisted laparoscopic pelvic mass resection and now follows up annually with imaging for observation.

In this case report, we describe a diagnosis of papillary renal cell carcinoma in a 76-year-old male patient who was incidentally found to have a left adrenal mass during routine aneurysm surveillance. Computed tomography demonstrated a left adrenal mass and left renal structure which was concerning for renal cell carcinoma. He underwent left adrenalectomy and initial histopathology demonstrated papillary renal cell carcinoma. He subsequently underwent left radical nephrectomy with lymph node dissection. Histopathological analysis of the removed left renal and nodal specimens revealed papillary renal cell carcinoma with lymph node metastasis. However, re-review of the adrenal pathology slides determined the specimen as represented by primary kidney tumor and not adrenal metastasis. This report reviews the presentation and radiological findings of synchronous papillary renal cell carcinoma and differential diagnosis for indeterminate adrenal mass on computed tomography.

BACKGROUND: Undifferentiated carcinomas of the pancreas with osteoclast-like giant cells (UCPOGC) are rare pancreatic neoplasms that account for less than 1% of all pancreatic malignancies. This case report of a 54-year-old male with metastatic UCPOGC adds to the existing literature and further ascertains the clinical and imaging features, treatment options, and prognosis of this rare entity. CASE PRESENTATION: We present the detailed clinical course of a 54-year-old Asian male patient with UCPOGC, with focus on the relevant clinical features and imaging findings that are characteristic of this disease entity. CONCLUSIONS: UCPOGC is an extremely rare pancreatic tumor with a unique histopathology and clinical course. It is often difficult to distinguish UCPOGCs from other pancreatic tumors, such as traditional pancreatic ductal adenocarcinomas (PDAC), on imaging, and it therefore remains a pathological diagnosis. Surgery is generally regarded as the first-line treatment option, and the roles of chemotherapy and radiation are unclear. Due to the exceeding rarity of this tumor, large-scale clinical studies are not feasible. Therefore, it is important to share individual insights and experiences to improve our understanding and care for patients with this devastating disease.

Phosphaturic mesenchymal tumor (PMT) is a rare tumor causing bone complications and myopathy. Histologically, PMT displays a mix of spindled cells, osteoclast-like giant cells, basophilic matrix, and flocculent or grungy calcification. Here we describe a case of PMT in the right hip and proximal femur, initially suspected to be multiple myeloma, presenting with osteolytic lesions and elevated alkaline phosphatase. Tests for malignancy were negative, but a subsequent biopsy confirmed PMT. The patient underwent hip biopsy, femur resection, and hemiarthroplasty, with follow-up MRI recommended.

Polypoid pyeloureteritis is a rare benign exophytic mucosal lesion of the renal pelvis and ureter caused by recurrent inflammation. Risk factors include a history of radiation therapy, colovesical fistulas, or calculi. To our knowledge, we present the first documented case of polypoid pyeloureteritis with radiologic, pathologic, and clinical correlation. A 74-year-old male with a history of right papillary renal cell carcinoma status-post nephrectomy and recurrent nephrolithiasis presented for computed tomography urography for carcinoma surveillance. Computed tomography urography revealed urothelial thickening at the left renal pelvis along with small polypoid filling defects in the left renal collecting system at the ureteropelvic junction, as well as a 3mm nonobstructing stone. Biopsy of the lesion confirmed the diagnosis of polypoid pyelitis with ureteritis. Lithotripsy for stone removal was administered at the time of biopsy, and fulguration of the mass was performed. At the time of 1-year follow-up the patient denied any complaints, including urinary symptoms. Imaging was once again remarkable for extensive urothelial thickening of the left renal pelvis and proximal ureter that demonstrated subtle nodularity, consistent with known polypoid pyeloureteritis. Clinical context and pathologic findings should be considered to differentiate benign polypoid lesions from urothelial neoplasms after observing urothelial thickening and filling defects on computed tomography urography. If the lesion is non-neoplastic, fulguration combined with removal of the irritant may serve as an alternative management for surgical excision.

During thymocyte development, medullary thymic epithelial cells (mTECs) provide appropriate instructive cues in the thymic microenvironment for not only negative selection but also the generation of regulatory T (T reg) cells. Here, we identify that miR-155, a microRNA whose expression in T reg cells has previously been shown to be crucial for their development and homeostasis, also contributes to thymic T reg (tT reg) cell differentiation by promoting mTEC maturation. Mechanistically, we show that RANKL stimulation induces expression of miR-155 to safeguard the thymic medulla through targeting multiple known and previously uncharacterized molecules within the TGFβ signaling pathway, which is recognized for its role in restricting the maturation and expansion of mTECs. Our work uncovers a miR-155-TGFβ axis in the thymic medulla to determine mTEC maturity and, consequently, the quantity of tT reg cells and suggests that miR-155 ensures proper tT reg cell development in both cell-intrinsic and -extrinsic manners.