PMC10011866_01
Case 1 imaging. Coronal contrast-enhanced pediatric protocol low dose CT showed a left prevascular mediastinal mass (arrow) that is well-circumscribed, and lobulated, with serpiginous heterogeneous enhancement. CT, computed tomography.
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Chest CT with contrast showed a large lobulated, heterogeneous, and vascular left prevascular mediastinal mass isodense to surrounding soft tissue, with internal areas of enhancement (Figure 1).
Case 1 first biopsy. CT-guided biopsy was nonspecific. There was scant fibroconnective tissue with variable collagenization, myxoid change, and myofibroblasts (H&E stain; original magnification: 100x). Additional tissue sampling was recommended. CT, computed tomography; H&E, hematoxylin and eosin.
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CT-guided biopsy yielded scant fragments of fibroconnective tissue with variable collagenization and myxoid change (Figure 2) associated with irregular and thin ectatic vessels.
Case 1 second biopsy. Open biopsy showed extensive fibrosclerosis, lymphoplasmacytic infiltration, and thin dilated vessels (H&E stain; original magnification: 100x). H&E, hematoxylin and eosin.
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An open biopsy (Chamberlain procedure) showed extensive fibrosclerosis, lymphoplasmacytic inflammatory infiltration, and thin dilated vessels (Figure 3).
Case 1 resection. Gross examination of the resection specimen showed a 115.6 g, 7.0 cm x 6.9 cm x 4.3 cm irregular well-circumscribed, red-pink firm mass with mottled fibrotic cut surfaces (A). Only approximately 5% of the mass showed tumor cells, mostly along the periphery and involving adjacent thymic parenchyma (B, middle and bottom; H&E stain; original magnification: 20x). The remainder of the mass consisted of inflamed vascular sclerotic tissue suggestive of regression (B, upper right). The tumor component consisted of sheets of medium-sized tumor cells with relatively uniform, large central nuclei with prominent nucleoli, and amphiphilic to clear cytoplasm (C; H&E stain; original magnification: 100x). The tumor cells were positive for immunostains OCT-4, PLAP, and D2-40, consistent with seminoma (D, E, F, respectively; immunohistochemical stains; original magnification: 100x). H&E, hematoxylin and eosin; OCT-4, octamer-binding transcription factor-4; PLAP, placental-like alkaline phosphatase; D2-40, podoplanin.
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Gross exam showed a 7.0 cm x 6.9 cm x 4.3 cm irregular circumscribed red-pink firm mass with mottled fibrotic cut surfaces (Figure 4A). The malignant cells were located mostly along the periphery of the mass and involved adjacent thymic parenchyma (Figure 4B,4C). IHC showed the tumor cells were diffusely and strongly positive for octamer-binding transcription factor-4 (OCT-4), cluster of differentiation 117 (CD117), placental-like alkaline phosphatase (PLAP) (Figure 4D-4F), and podoplanin (D2-40), while negative for AFP and S100 protein.
PMC10011866_02
Case 2 imaging. Axial CT angiogram of the chest showed a prevascular mediastinal mass (yellow arrow) with small peripheral calcifications (blue arrow). CT, computed tomography.
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CT pulmonary angiogram demonstrated pulmonary embolism, as well as an incidental large prevascular mediastinal mass with small peripheral calcifications (Figure 5).
Case 2 biopsy. During CT-guided biopsy, the needle (A, arrow) entered a non-FDG-avid portion of the mass (B; PET scan; arrow corresponds to biopsied area shown in A). The biopsy demonstrated hypocellular dense fibrous tissue (C; H&E stain; original magnification: 100x) that was negative for Congo red, STAT6, S100 protein, and beta-catenin. CT, computed tomography; FDG, fluorodeoxyglucose; PET, positron emission tomography; H&E, hematoxylin and eosin.
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CT-guided biopsy was performed, with the needle (Figure 6A) passing through a portion of the mass that was not FDG-avid (Figure 6B). The biopsy demonstrated hypocellular dense fibrous tissue (Figure 6C).
Case 2 resection. Gross examination of the resection specimen showed a 7.0 cm x 6.0 cm x 1.5 cm tan-white lobulated firm tumor with focal hemorrhage on cut sections (A). Approximately 50% of the tumor showed dense hypocellular fibrotic tissue with irregular thin ectatic vessels, suggestive of regression (B, left; H&E stain; original magnification: 40x). The tumor consisted of sheets and nests of medium sized tumor cells separated by fibrous septa. The tumor cells had amphiphilic to clear cytoplasm with relatively uniform, large central nuclei and prominent nucleoli. A lymphoplasmacytic infiltrate was seen in the fibrous septa (C; H&E stain; original magnification: 100x). The tumor cells were positive for immunostains OCT-4, CD117, SALL4 (D, E, F, respectively; immunohistochemical stains; original magnification: 100x), keratin CAM 5.2 (dot-like cytoplasmic pattern), and D2-40, while negative for Glypican-3 and CD30, consistent with seminoma. H&E, hematoxylin and eosin; OCT-4, octamer-binding transcription factor-4; CD117, cluster of differentiation 117; SALL4, spalt like transcription factor 4; D2-40, podoplanin; CD30, cluster of differentiation 30.
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Gross examination demonstrated a 7 cm x 6 cm x 1.5 cm lobulated tan-white firm tumor with focal hemorrhage (Figure 7A). The resection additionally showed areas within the fibrosis that contained irregular thin ectatic vessels similar to the first case (Figure 7B). A lymphoplasmacytic infiltrate was seen in the fibrous septa (Figure 7C). IHCs showed the tumor cells were positive for OCT-4 (Figure 7D), CD117 (Figure 7E), SALL4 (Figure 7F), pancytokeratin CAM 5.2 (dot-like cytoplasmic pattern), and D2-40, while negative for Glypican-3 and cluster of differentiation 30 (CD30), which confirmed the diagnosis of seminoma.