case_images: PMC10614567_01
case_images: Pleural fluid sample from the initial thoracentesis. The cells within this sample were obtained 6 months before the PEL diagnosis, as seen in the cell block (hematoxylin/eosin stain, x20 original magnification with x40 inset (a)), thin prep (Papanicolaou smear, x20 original magnification with x40 inset (b)), and cytospin (Giemsa stain, x20 original magnification with x40 inset (c)), and consisted of lymphocytes, histiocytes, and mesothelial cells. The cells were negative for KSHV (LANA/HHV8) (immunoperoxidase, x20 original magnification (d)) and negative for EBV (EBER) (in situ hybridization, x20 original magnification (e)). CD45 highlighted the hematopoietic cells (immunoperoxidase, x20 original magnification (f)).
case_images: pat-2023-0090-0005-530429_F01.jpg
case_images: PMC10614567_01_pat-2023-0090-0005-530429_F01.jpg
case_images: F1
case_images: A thoracentesis, with removal of 1,500 mL of serosanguinous pleural fluid, was performed, which based on cytologic examination, did not contain neoplastic cells (Fig. 1a-c). Immunohistochemistry performed on the cell block for KSHV (latency-associated nuclear antigen [LANA]/HHV8) was negative (Fig. 1d) as was in situ hybridization for EBV (EBER) (Fig. 1e). CD45 (Fig. 1f) and calretinin highlighted the hematopoietic and mesothelial cells, respectively. Concurrent pleural fluid flow cytometric analysis showed no immunophenotypic evidence of a hematolymphoid neoplasm.
case_images: Pleural fluid sample from the thoracentesis at the time of PEL diagnosis, as seen in the cell block (hematoxylin/eosin stain, x20 original magnification with x40 inset (a)), thin prep (Papanicolaou smear, x20 original magnification with x40 inset (b)), and cytospin (Giemsa stain, x20 original magnification with x40 inset (c)), and consisted of atypical cells with pleomorphic nuclei and abundant cytoplasm. The atypical cells were positive for KSHV (LANA/HHV8) (immunoperoxidase, x20 original magnification with x40 inset (d)) and weakly positive for EBV (EBER) (in situ hybridization, x20 original magnification with x40 inset (e)). Malignant cells stained positive for CD38 (f), CD138 (g), CD30 (h), and MUM-1 (i). CD45 highlighted the hematopoietic cells (j), and calretinin highlighted the few associated mesothelial cells (k) (immunoperoxidase, x20 original magnification (f-k)).
case_images: pat-2023-0090-0005-530429_F02.jpg
case_images: PMC10614567_01_pat-2023-0090-0005-530429_F02.jpg
case_images: F2
case_images: Pleural fluid cytology showed medium to large-sized atypical cells with amphophilic cytoplasm containing vacuoles and irregular nuclei with prominent nucleoli (Fig. 2a-c). Immunohistochemistry performed on the cell block of this specimen showed that the aberrant cells were positive for CD45, MUM-1, CD38, CD138, CD30, and LANA/HHV8 (Fig. 2) and negative for CD20, PAX5, CD3, CD34, CD117, CD163, and EMA. In situ hybridization showed that the cells were negative for kappa and lambda light chain expression but were weakly positive for EBV (EBER) (Fig. 2e). In addition, the atypical cells were negative for the mesothelial markers calretinin (Fig. 2k) and WT-1 and the epithelial markers CK5/6, Ber-EP4, B72.3, and claudin-4.