If malignancy is suspected, histochemical, ICC, and other ancillary techniques can be performed on cell blocks to increase diagnostic accuracy

Histochemical stains and ICC can be done on cell blocks because multiple duplicate slides can be obtained

Sensitivity increases to 83-85% when ≥ 2 preparation methods are utilized (e.g., cytocentrifuge and cell block)

Traditionally, cell blocks are prepared from cell pellet using plasma thrombin clot or HistoGel method

ICC and molecular testing can also be performed utilizing Cellient cell blocks

Reactive mesothelial cells can have significant cytologic atypia and thus mimic carcinomas

Malignant mesotheliomas can present as 3D clusters and papillary groups that simulate carcinomas

Histochemical stains that aid in DDx include mucicarmine stain and PAS diastase

GMS, AFB, Fite, and mucicarmine stains are some of the histochemical stains that can be used to detect mycobacterial or fungal organisms

ICC stains and molecular testing can be utilized to detect viral organisms

Highly cellular specimens with atypical cytologic features can mimic adenocarcinoma

ICC stains are helpful in determining possible primary site, especially in patients with occult primary and in patients with history of multiple primary malignancies

Consider cytomorphology, site of effusion, gender, and clinical history in order to perform most specific markers

General adenocarcinoma markers coupled with more specific markers are often helpful