case_images: PMC11809604_01
case_images: CT of the chest with contrast demonstrating an 8.7 x 7.1 x 4 soft tissue mass extending along the middle and posterior mediastinum into the left hilum (arrow). The lesion is exerting mass effect on the left atrium, encasing several pulmonary veins, and effacing the fat plane along the anterior esophagus with esophageal wall thickening. CT: computed tomography.
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case_images: PMC11809604_01_jmc-16-048-g001.jpg
case_images: F1
case_images: Computed tomography (CT) of the thorax with contrast revealed an 8.7 x 7.1 x 4 cm soft tissue mass extending along the midline and posterior mediastinum into the left hilum (Fig. 1). This lesion exerted a mass effect on the left atrium and encased several pulmonary veins, resulting in mild narrowing of the right inferior pulmonary vein, severe narrowing of the left superior pulmonary vein, and near-complete occlusion of the left inferior pulmonary vein (Fig. 1). There was also effacement of the fat plane along the anterior esophagus with esophageal wall thickening, raising concerns for possible involvement (Fig. 1).
case_images: CT thorax with contrast demonstrating a large pleural effusion occupying the majority of the left hemithorax (arrows). CT: computed tomography.
case_images: jmc-16-048-g002.jpg
case_images: PMC11809604_01_jmc-16-048-g002.jpg
case_images: F2
case_images: Additionally, there was a small left pleural effusion, which eventually developed into a large pleural effusion occupying the majority of the left hemithorax, with loculated fluid along the left anteromedial hemithorax (Fig. 2).
case_images: Primary effusion lymphoma. (a) Sheets of large pleomorphic lymphoma cells with prominent nucleoli and abundant cytoplasm, morphologically consistent with EC-PEL (H&E stain, original magnification: x 400). (b) Cytospin smear of pleural fluid showing PEL (Wright-Giemsa stain, original magnification: x 600). (c) Strong positive immunostaining for CD138 in neoplastic cells (immunohistochemistry, original magnification: x 400). (d) Strong positive immunostaining for MUM-1 in neoplastic cells (immunohistochemistry, original magnification: x 400). (e) The lymphoma cells demonstrate strong positive immunostaining for HHV8 (immunohistochemistry, original magnification: x 400). (f) Weak positive immunostaining for CD45 in neoplastic cells (immunohistochemistry, original magnification: x 400). (g) A small subset of neoplastic cells showed positive immunostaining for CD3 (immunohistochemistry, original magnification: x 400). (h) In situ hybridization for EBER was positive in the lymphoma cells (original magnification: x 400). EBER: Epstein-Barr virus-encoded RNA; EC-PEL: extracavitary primary effusion lymphoma; H&E: hematoxylin and eosin stain; PEL: primary effusion lymphoma.
case_images: jmc-16-048-g003.jpg
case_images: PMC11809604_01_jmc-16-048-g003.jpg
case_images: F3
case_images: Endoscopic ultrasound-guided fine needle biopsy of the mediastinal mass revealed sheets of large pleomorphic lymphoma cells with prominent nucleoli and abundant cytoplasm (Fig. 3a). Immunohistochemical (IHC) stains showed the lymphoma cells were positive for CD138 (Fig. 3c), multiple myeloma oncogene 1 (MUM-1) (Fig. 3d), and HHV8 (Fig. 3e), weakly positive for CD45 (Fig. 3f), with a small subset positive for CD3 (Fig. 3g). Additionally, Epstein-Barr virus-encoded RNA (EBER) in situ hybridization (ISH) was positive (Fig. 3h). Later, a cytospin smear of his pleural fluid also demonstrated large lymphoma cells with marked pleomorphism, prominent nucleoli, and deep blue plasmacytoid cytoplasm (Fig. 3b), consistent with the diagnosis of PEL.