Presenting Author Information
Swikrity Upadhyay Baskota, MD
UPMC Shadyside Hospital
Pittsburgh, PA

Second Author Information
Samer Khader, MD
University of Pittsburgh Medical Center (UPMC) Shadyside Hospital
Pittsburgh, PA

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Objective 1: To understand the cytomorphology of Epithelioid Hemangioendothelioma (EHE).

Objective 2: To review the ancillary tests required for the diagnosis of Epithelioid Hemangioendothelioma.

Objective 3: To list the differential diagnosis of Epithelioid Hemangioendothelioma in an effusion cytology.

Clinical History
A female in her forties with a significant past medical history of intermediate grade soft tissue neoplasm of lung, with invasion of anterior left 4th-9th ribs. She was treated by resection,
localized radiation therapy and systemic chemotherapy, now presents with increasing left sided pleural effusion. An anterior chest x-ray shows moderate left-sided pleural effusion. Diagnostic
left pleural thoracentesis fluid was sent for cytologic evaluation.

Features:
The liquid based Cytology preparations (ThinPrep) (Figure 1-4, pre-test) and cell block preparations (Figure 5-6, pre-test) demonstrate increased cellularity with neoplastic cells arranged singly and in loose clusters, with minimal to moderate amount of cytoplasm, and eccentric nuclei (plasmacytoid cells). Some of the cells appear epithelioid with increased nuclear to cytoplasmic ratio, irregular nuclear membranes, multi-nucleation and prominent nucleoli. The chromatin ranges from finely granular to coarse. Immunostains performed on the cellblock (Figure 1-4, post-test) reveal that the tumor cells are positive for CD34 (Figure 1, post-test), CD31 (Figure 2, post-test), ERG (Figure 3, post-test) and focally positive for pancytokeratin (Figure 4, post-test). The tumor cells are negative for calretinin, CD68, and EMA.

Figure 1: Pleural Fluid, Thin prep, Diff-Quik stain, 20x. A cluster of neoplastic epithelioid cells with eccentrically placed nuclei and abundant cytoplasm with some background macrophages.

Figure 2: Pleural Fluid, Thin prep, Diff-Quik stain, 20x. Two malignant epithelioid cells demonstrating pleomorphism and a cytoplasmic vacuole.

Figure 3: Pleural Fluid, Thin prep, Papanicolaou stain, 20x. A cluster of neoplastic epithelioid cells with moderate to abundant cytoplasm, eccentric nuclei, and eosinophilic globules in the cytoplasm.

Figure 4: Pleural Fluid, Thin prep, Papanicolaou stain, 20x. A cluster of malignant epithelioid cells with abundant cytoplasm, eccentric nuclei, and eosinophilic globules with associated red blood cells.

Figure 5: Pleural Fluid, Cell block, H&E stain, 10x. A low power view of malignant epithelioid cells mixed with mesothelial and inflammatory cells.

Figure 6: Pleural Fluid, Cell block, H&E stain, 20x. An intermediate power view of malignant epithelio orphism mixed with mesothelial and inflammatory cells.