Akihiko Sugimoto

<jats:p>A 22-year-old woman with von Hippel-Lindau (VHL) disease presented with a hypervascular mesorectal mass (44×38 mm). Imaging revealed features consistent with VHL-associated cystadenomas, such as a sponge-like appearance, high signal intensity on T2-weighted images, and early enhancement. The possibility of a highly malignant tumor was excluded based on high ADC values, low FDG uptake, and minimal size change. Biopsy confirmed benign papillary cystadenoma, similar to other VHL-associated tumors. It is important to be aware that papillary cystadenomas can arise in unexpected locations in patients with VHL disease, and that recognizing characteristic imaging and pathologic features could facilitate early diagnosis and clinical decision-making, even if tumors arose in atypical sites.</jats:p>

<jats:p>A 69-year-old man presented with hoarseness and cervical swelling. CT revealed a neck tumor and lymph node metastasis. Somatostatin receptor scintigraphy (SRS) showed mild lesion uptake. Intravenous tumor thrombus into the right internal jugular and vertebral vein was suggested by FDG-PET/CT and confirmed by Contrast-enhanced CT. Biopsy revealed squamous cell carcinoma (SCC). The tumor location and thrombosis suggested ectopic thymic origin. Immunostaining for markers CD117 and POU2F3 was positive, confirming ectopic thymic SCC. Chemotherapy was initiated, with tumor reduction after 6 months. This case highlights the usefulness of FDG-PET/CT suggestion of tumor thrombus and SRS accumulation in the diagnosis of ectopic thymic carcinoma.</jats:p>

Epstein-Barr Virus (EBV)-positive inflammatory follicular dendritic cell sarcoma (EBV-IFDCS) is a rare tumor of low malignant potential. Abundant lymphocytes and plasma cells often infiltrate into this tumor tissue with lymphoid follicles and sarcoid-like granulomas, so that the differential diagnosis of this tumor includes inflammatory lesions such as IgG4-related disease, morphologically. This tumor typically arises in the spleen or liver, and shows follicular dendritic cell (FDC)-like immunophenotype. Here we presented a case of EBV-IFDCS arising in intrapancreatic accessory spleen, which was preoperatively considered as a pancreatic tumor. Immunohistochemistry revealed its fibroblastic reticular cell-like phenotype, namely alpha SMA, l-caldesmon, tenascin C, and transglutaminase II positivity, while FDC marker expression such as CD21 and clusterin was focal. Positivity for EBV-encoded small RNA in situ hybridization (EBER ISH) distinguished it from inflammatory lesions or conventional FDC sarcoma. The differential diagnosis of EBV-IFDCS is broad, ranging from non-neoplastic lesions to sarcoma, particularly when it arises in unusual sites. Therefore, careful gross and microscopic examination and adequate immunohistochemistry application including EBER ISH are important to diagnose it properly.

Erdheim-Chester disease (ECD) is a rare type of non-Langerhans cell histiocytosis, characterized by the infiltration of disease-specific foamy histiocytes, polymorphic granulomas, and fibrosis. Although cardiovascular involvement is observed radiologically in approximately half of ECD patients, only a few reports have described its pathological features. We herein report the autopsy of an ECD patient with pulmonary, cardiovascular, and retroperitoneal involvement that may have caused his death. Autopsy revealed the pathological association of coronary and renal arterial stenosis with the BRAF^V600E gene mutation. BRAF mutations should be considered in patients with ECD, especially in those with arterial lesions.

<h4>Background</h4>Chondrosarcoma is typically a slow-growing tumor, and intratumoral hemorrhage is rare. Acute brainstem hemorrhage due to chondrosarcoma has rarely been reported.<h4>Observations</h4>A 77-year-old man presented with the sudden onset of headache and vomiting followed by a declining level of consciousness, progressive right hemiparesis, and left ophthalmoplegia. Magnetic resonance imaging showed pontine hemorrhage and a mass in the retroclival space compressing the brainstem. Emergency endoscopic endonasal surgery was performed. Intraoperative observation revealed that a hematoma was located in the pons and subdural space around the tumor mass, suggesting that the hematoma had likely been caused by the rupture of small vessels around the pons, not by intratumoral hemorrhage. The pathological diagnosis was chondrosarcoma. The patient recovered well and underwent radiotherapy.<h4>Lessons</h4>This report describes a case of sudden neurological deterioration due to hemorrhage in a patient with chondrosarcoma of the skull base. An emergency endoscopic endonasal approach for mass reduction and hematoma removal was effective in the acute setting. This approach revealed the suspected etiology of peritumoral hemorrhage, not intratumoral hemorrhage. https://thejns.org/doi/10.3171/CASE2460.