Podoplanin (D2-40)

D2-40 is an antibody used in pathology that binds to a protein called podoplanin. Mesothelioma cells (especially the epithelioid type) typically stain positive for D2-40, so pathologists use it as one of several markers to confirm a mesothelioma diagnosis and to distinguish it from lung cancers (such as adenocarcinoma) that have spread to the pleura.

Origin

D2-40 is the laboratory clone name of the monoclonal antibody, originally developed in the early 2000s against an oncofetal testicular antigen and later shown to recognize podoplanin. Podoplanin itself was named from the Greek podo- (foot) and planus (flat), reflecting its discovery on the foot processes of kidney podocytes.

Significance in Asbestos Context

When a biopsy is taken to investigate possible mesothelioma, the pathologist runs a panel of immunohistochemical stains rather than relying on appearance alone. A positive D2-40 result, combined with other positive mesothelial markers (such as calretinin and WT-1) and negative carcinoma markers (such as TTF-1, Ber-EP4, or claudin-4), strongly supports a mesothelioma diagnosis. This distinction matters enormously to patients: the diagnosis determines treatment options, prognosis, and eligibility for asbestos trust claims and lawsuits, all of which generally require a confirmed mesothelioma diagnosis supported by immunohistochemistry. D2-40 is most informative for epithelioid and biphasic mesothelioma; sarcomatoid mesothelioma often stains weakly or not at all, so a negative result does not rule out the disease.

Example Sentence

"Her pathology report showed strong D2-40 and calretinin staining with negative TTF-1, which the oncologist explained confirmed epithelioid mesothelioma rather than metastatic lung cancer."

Related Terms

Immunohistochemistry, Calretinin, WT-1, Epithelioid Mesothelioma, Mesothelioma, Pathology Review

Notes

• Ask your oncologist or pathologist for a copy of the immunohistochemistry panel from your biopsy report. D2-40 should appear alongside several other markers, and the full panel is often required by attorneys and asbestos trusts.
• If your initial biopsy is inconclusive or only one or two stains were run, request a second pathology opinion at a mesothelioma specialty center (such as an NCI-designated cancer center); expert re-review using a full marker panel including D2-40 frequently clarifies the diagnosis.
• Preserve the original paraffin tissue blocks and slides. These are the physical samples used for D2-40 staining and may be needed later for additional testing, expert review, or legal evidence. Hospitals do not keep them forever, and your legal team may need to request them.
• A negative D2-40 does not rule out mesothelioma, especially the sarcomatoid subtype; additional markers and clinical correlation are needed.