IHC - Round Cell Panel

The IHC score (immunohistochemistry) quantifies protein expression in tumor cells by combining staining intensity and proportion of positive cells. Scales include HER2: 0, 1+, 2+ (equivocal), 3+ (positive); Allred score: 0–8 (ER/PR); and H‑score: 0–300 (percent cells × intensity). IHC results guide prognosis and treatment; equivocal findings often need confirmatory testing (e.g., FISH).

The five classic round-cell tumors are: lymphoma; plasma-cell tumors (plasmacytoma/multiple myeloma); mast-cell tumor; histiocytic tumors (including histiocytoma); and transmissible venereal tumor (TVT). These neoplasms are composed of round cells and often affect lymphoid or cutaneous tissues. Definitive diagnosis relies on cytology or biopsy with immunophenotyping to guide treatment.

Immunohistochemistry (IHC) helps identify and subtype many cancers by detecting tumor‑specific markers. Commonly used in breast (ER/PR/HER2), lung (TTF‑1, Napsin A), colorectal (CK20, CDX2), prostate (PSA), melanoma (S100, HMB‑45), lymphomas (CD20, CD3), gynecologic and renal tumors (PAX8), liver and various sarcomas. IHC guides diagnosis, origin determination, prognosis and therapy selection.

The six commonly used immunohistochemistry markers are: cytokeratins (epithelial differentiation), vimentin (mesenchymal), CD45/LCA (hematolymphoid cells), S100 (neural/melanocytic), Ki‑67 (proliferation index), and p53 (tumor suppressor/oncogenic alterations). Selection depends on clinical context, morphology, and differential diagnosis; panels often combine lineage and functional markers.

If an immunohistochemistry (IHC) test is positive, it means the tissue expresses the specific protein marker tested. This helps confirm diagnosis (for example tumor type/subtype), refines prognosis, and can guide targeted therapies. Results are interpreted by a pathologist with other tests; sometimes repeat or supplementary testing is needed to resolve equivocal or false-positive findings before clinical decisions are made.

There’s no single “good” cancer‑marker number. Each marker (PSA, CA‑125, CEA, etc.) has its own lab reference range, and values within that range are generally considered normal. More important is change over time: stable or falling levels are reassuring, while rising levels warrant further evaluation. Always interpret results with clinical context and discuss them with your doctor.