case_images: PMC11146452_01
case_images: Radiographic and pathological images of Case No. 1: (A) CT scan of the chest (axial plane) showing a 1.3 cm nodule located beneath the pleura in the lower left lung; (B) Follow-up CT scan three years later revealing the lesion stable; (C) Core-needle biopsy showing that the tumor was primarily composed of spindle-shaped cells set in fascicular arrangements; (D) High-power view exhibiting tumor cells with mild pleomorphism and minimal nuclear atypia; (E) Certain areas of tumor displaying hemangiopericytoma-like branching vascular pattern; (F) The tumor cells were positive for alpha-SMA; (G) ISH revealed nuclear positive signals for EBER; (H) EBNA2 nuclear positive staining in tumor cells. HE staining: (C and E) x100; (D) x400. alpha-SMA immunostaining: (F) x400. EBER ISH analysis: (G) x400. EBNA2 immunostaining: (H) x400. alpha-SMA: Alpha-smooth muscle actin; CT: Computed tomography; EBER: Epstein-Barr virus (EBV)-encoded small ribonucleic acid; EBNA2: EBV nuclear antigen 2; HE: Hematoxylin-Eosin; ISH: In situ hybridization
case_images: RJME-65-1-107-fig1.jpg
case_images: PMC11146452_01_RJME-65-1-107-fig1.jpg
case_images: F1
case_images: The pre-contrast mean CT value of the largest nodule was 4 HU, whereas the enhanced mean CT value was 70 HU, indicating obvious enhancement (Figure 1A). The lesion mainly consisted of spindle cells arranged in fascicles (Figure 1C), with moderate amounts of eosinophilic cytoplasm and elongated nuclei. Tumor cells showed mild nuclear pleomorphism with minimal atypia, and mitotic figures were infrequent (Figure 1D). Prominent branching thin-walled blood vessels were observed in the background (Figure 1E), and intratumoral lymphocytic infiltration was occasionally seen. By immunohistochemistry, the tumor cells expressed alpha-smooth muscle actin (alpha-SMA) (Figure 1F) and vimentin but did not express cluster of differentiation (CD)34, KIT, CD21, anaplastic lymphoma kinase (ALK), signal transducer and activator of transcription 6 (STAT6), CD45, S100, human melanoma black 45 (HMB45), h-caldesmon, pan-cytokeratin (CK) AE1/AE3, CK7, epithelial membrane antigen (EMA), estrogen receptor (ER), or CD10. Tumor cells were also positive for EBV-encoded small ribonucleic acid (RNA) (EBER) ISH (Figure 1G). Subsequently, additional immunohistochemical (IHC) staining for Epstein-Barr virus nuclear antigen 2 (EBNA2) showed nuclear positivity in tumor cells (Figure 1H). Over a follow-up period of 60 months, regular chest CT scans had shown that the number and size of nodules remained stable, with the largest nodule diameter fluctuating between 1.2 cm and 1.5 cm (Figure 1A, 1B).
case_images: PMC11146452_02
case_images: Radiographic and pathological images of Case No. 2: (A) Plain chest CT image illustrating a circular nodule in the left upper lobe of the lung; (B) Gross examination showing grayish-white well-circumscribed mass in the cut section; (C) Whole slide image showing the lesion was circumscribed but not encapsulated (HE staining). Scale bar: (B) 1 cm; (C) 1000 mum. CT: Computed tomography; HE: Hematoxylin-Eosin
case_images: RJME-65-1-107-fig2.jpg
case_images: PMC11146452_02_RJME-65-1-107-fig2.jpg
case_images: F2
case_images: After four months of observation, it was discovered that the nodule located in the left upper lung had rapidly increased in size to approximately 1.1x1.0x0.9 cm3 (Figure 2A). Grossly, the lesion presented as a nodular mass, measuring approximately 0.85x0.85x0.8 cm3 in size, with a blurred scar visible at the center of the cut surface (Figure 2B). On the whole slide image, the lesion appears as an oval mass with sharp delineation from the surrounding lung tissue, without obvious capsule (Figure 2C).
case_images: Pathological images of Case No. 2: (A) High-power view of a representative area demonstrating the morphology of the tumor, containing atypical mitotic figure (white arrow); (B) Tumor cells stained for alpha-SMA; (C) Tumor cells stained for EBNA2; (D) EBER ISH showing strong nuclear staining in most tumor cells. HE staining: (A) x400. alpha-SMA immunostaining: (B) x400. EBNA2 immunostaining: (C) x400. EBER ISH analysis: (D) x400. alpha-SMA: Alpha-smooth muscle actin; HE: Hematoxylin-Eosin. EBER: Epstein-Barr virus (EBV)-encoded small ribonucleic acid; EBNA2: EBV nuclear antigen 2; HE: Hematoxylin-Eosin; ISH: In situ hybridization
case_images: RJME-65-1-107-fig3.jpg
case_images: PMC11146452_02_RJME-65-1-107-fig3.jpg
case_images: F3
case_images: Atypical mitotic figures were occasionally observed (Figure 3A), but no necrosis was noted. Immunohistochemically, the tumor cells were strongly positive for vimentin, alpha-SMA (Figure 3B) and EBNA2 (Figure 3C), while negative for desmin, pan-CK AE1/AE3, h-caldesmon, ALK, CD34, calponin, S100, CD21, CD35, CD207, and CD1alpha. ISH for EBER showed more than 60% of neoplastic cells were positive stained (Figure 3D).