Effusion cytology
IHC panels

Last author update: 8 August 2022
Last staff update: 8 August 2022

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PubMed Search: Immunostaining panels effusion cytology

Lawrence Hsu Lin, M.D., Ph.D.
Tamar C. Brandler, M.D., M.S.
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Cite this page: Lin LH, Brandler TC. IHC panels. website. Accessed September 25th, 2023.
Definition / general
  • Serous cavities can be involved by metastatic neoplasms, inflammatory / infectious conditions or primary malignancies
  • Immunostaining panels with correlation with cytomorphology and clinical information can aid in the differential diagnosis of serous fluid effusion
Essential features
CPT coding
  • 88108 - concentrated cytology specimen (e.g., centrifugation)
  • 88112 - selective enhanced cytology specimen (e.g., liquid based slide preparation)
  • 88305 - cell block
  • 88342 - immunohistochemistry, first stain
  • 88341 - immunohistochemistry, additional stains
  • Pleura, peritoneum, pericardium
Diagrams / tables

Contributed by Lawrence Hsu Lin, M.D., Ph.D. and Tamar C. Brandler, M.D., M.S.

Serous fluid immunostain work up

Cytology description
  • Use of immunostaining panel with multiple stains is beneficial since no single stain has 100% sensitivity or specificity
  • Positive stains are more useful than negative stains since a larger percentage of cases in effusion can lose expression as compared with primary tumors
  • Cytomorphology and correlation with clinical and radiological information can tailor immunostains panel in order to make the following differential diagnoses:

      • Immunostains and special stains to differentiate mesothelioma from metastatic carcinoma (Hum Pathol 2013;44:1, Cancer Cytopathol 2014;122:299, Transl Lung Cancer Res 2020;9:S3):
        Metastatic carcinoma Mesothelioma
        Calretinin Negative (can be positive in breast cancer, squamous cell carcinoma) Positive (nuclear and cytoplasmic)
        D2-40 Negative (can be positive in breast, lung and ovarian cancer) Positive (membranous)
        WT1 Negative (can be positive in gynecologic tumors) Positive (nuclear)
        CK5/6 Negative (positive in squamous cell carcinoma) Positive (cytoplasmic / membranous)
        Claudin4 Positive (membranous) Negative
        MOC31 Positive (membranous) Negative
        BerEP4 Positive (membranous) Negative
        B72.3 Positive (cytoplasmic) Negative
        CEA Positive (cytoplasmic) Negative
        PASD Positive (cytoplasmic granules) Negative
        Mucicarmine Positive (cytoplasmic mucin) Negative

    • Immunostains to identify primary site or lineage of metastatic neoplasms (Cancer Cytopathol 2018;126:590, Adv Anat Pathol 2020;27:114, Hum Pathol 2013;44:1):
      • Lung adenocarcinoma: TTF1 and Napsin A
      • Thyroid: TTF1, PAX8, thyroglobulin
      • Breast: mammaglobin, GCDFP-15, GATA3, ER
      • Urothelial: p40 or p63 and GATA3
      • Gynecological tract: PAX8, ER
      • Lower gastrointestinal: CDX2, CK20 and SATB2
      • Hepatocellular carcinoma: Arginase1, HepPar1, Glypican 3
      • Renal cell carcinoma: PAX8, CAIX, RCC, CD10
      • Prostate: NKX 3.1, PSA
      • Squamous cell carcinoma: p40 and p63, CK5/6 (also positive in mesothelial cells)
      • Neuroendocrine neoplasm: synaptophysin, chromogranin, INSM1, CD56
      • Melanoma: SOX10, MelanA, S100, HMB45
      • Hematological neoplasm: CD45, B cell marker (CD20, CD79a, PAX5), T cell marker (CD3), plasma cell marker (CD138), HHV8 in primary effusion lymphoma
      • Vascular tumors: CD31, CD34, ERG
      • Germ cell tumors: PLAP, OCT 3/4, SALL4, HCG
      • Sex cord stromal tumors: calretinin (also positive in mesothelial cells), inhibin, SF1 and FOXL2

    • Predictive and prognostic markers performed on cell block (Chandra: The International System for Serous Fluid Cytopathology, 1st Edition, 2020, J Am Soc Cytopathol 2017;6:33, Arch Pathol Lab Med 2021;145:46, J Clin Oncol 2018;36:2105, Arch Pathol Lab Med 2018;142:291, Cancer Cytopathol 2015;123:117, Cancer Cytopathol 2018;126:421, Am J Surg Pathol 2017;41:1547, Cancer Cytopathol 2017;125:896):

      Immunostain Staining pattern Typically performed in Significance Additional testing
      ER / PR Nuclear Breast cancer Hormonal therapy for ER / PR positive tumors N/A
      HER2 Membranous Breast, gastric, gastroesophageal, endometrial cancer Anti HER2 therapy for HER2 positive tumors; specimens should be placed in 10% neutral buffered formalin as soon as possible and fixed for 6 - 72 hours FISH is used in equivocal results (2+)
      Mismatch repair proteins Nuclear Metastatic colorectal, endometrial, cholangiocarcinoma Immunotherapy for tumors with loss of mismatch repair protein PCR or NGS can be used to evaluate microsatellite instability
      ALK Cytoplasmic Non small cell lung cancer (NSCLC), inflammatory myofibroblastic tumor ALK inhibitors for tumors with ALK fusions or positive ALK immunostain FISH, PCR or NGS can be used as alternative to immunostaining
      ROS1 Cytoplasmic and membranous NSCLC ROS1 inhibitors for tumors with ROS1 fusions Immunostain is a screening method; FISH, PCR or NGS confirmation is necessary
      Pan TRK Nuclear, perinuclear, cytoplasmic and membranous Variety Anti NTRK therapy for tumors with NTRK fusions Immunostain is a screening method; molecular confirmation (typically NGS) is necessary
      PDL1 Membranous NSCLC Immunotherapy for PDL1 positive tumors; type of scoring and cut off points depend on antibody clone and type of tumor N/A
Cytology images

Contributed by Lawrence Hsu Lin, M.D., Ph.D. and Tamar C. Brandler, M.D., M.S.

BerEP4 in pleural fluid

MOC31 in pleural fluid

GATA3 in pleural fluid

PAX8 in pleural fluid

NKX3.1 in ascites

TTF1 in pleural fluid

Napsin A in pleural fluid

p40 in ascites

CDX2 in ascites

Calretinin in ascites

D2-40 in ascites

WT1 in ascites

ER in pleural fluid

HER2 in pleural fluid

Images hosted on other servers:

BAP1 in mesothelioma

Molecular / cytogenetics description
  • p16 / CDKN2A deletion by fluorescent in situ hybridization (FISH) is found in up to 80% of malignant mesothelioma and can help differentiate it from reactive mesothelial cells (Cancer Sci 2015;106:1635)
Molecular / cytogenetics images

Images hosted on other servers:

p16 / CDKN2A deletion (FISH) in malignant mesothelioma

Absence of p16 / CDKN2A deletion by FISH

Board review style question #1

Which immunostaining panel is most helpful in the differential diagnosis of a 60 year old male patient with unilateral pleural effusion with the above findings from the pleural fluid cytology smear stained with Papanicolaou stain?

  1. AE1 / AE3, CAM5.2, CK7, CK20
  2. BerEP4, MOC31, calretinin, D2-40, TTF1
  3. BerEP4, MOC31, CK7, CK20, TTF1
  4. Calretinin, D2-40, WT1, AE1 / AE3, CAM5.2
  5. TTF1, synaptophysin, chromogranin, Ki67
Board review style answer #1
B. BerEP4, MOC31, calretinin, D2-40, TTF1

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Reference: IHC panels
Board review style question #2
Which of the following immunostains can aid in the differentiation between a reactive mesothelial cells and mesothelioma?

  1. BAP1
  2. BerEP4
  3. Calretinin
  4. D2-40
  5. MOC31
Board review style answer #2

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Reference: IHC panels
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