Test Catalog

Test ID: PGM1    
CD68 (PG-M1) Immunostain, Technical Component Only

Useful For Suggests clinical disorders or settings where the test may be helpful

Identification of monocytic differentiation


Phenotyping hematolymphoid neoplasms that are suspected to represent histiocytic sarcomas

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

In normal tissues, CD68 PG-M1 stains monocytes, macrophages and, to a lesser extent, neutrophils in a cytoplasmic granular staining pattern. It has greater specificity for monocytes and macrophages than does KP-1 but its immunohistochemical staining pattern in non-hematolymphoid tumors has not been studied as extensively as CD68 KP-1. Diagnostically, CD68 PG-M1 is usually applied to cases of acute leukemia to demonstrate monocytic differentiation and to cases of hematolymphoid neoplasms that are suspected to represent histiocytic sarcomas.

Interpretation Provides information to assist in interpretation of the test results

This test does not include pathologist interpretation; only technical performance of the stain. If interpretation is required order PATHC / Pathology Consultation for a full diagnostic evaluation or second opinion of the case.


The positive and negative controls are verified as showing appropriate immunoreactivity and documentation is retained at Mayo Clinic Rochester. If a control tissue is not included on the slide, a scanned image of the relevant quality control tissue is available upon request, call 855-516-8404.


Interpretation of this test should be performed in the context of the patient's clinical history and other diagnostic tests by a qualified pathologist.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Age of a cut paraffin section can affect immunoreactivity. Stability thresholds vary widely among published literature and are antigen-dependent. Best practice is for paraffin sections to be cut within 6 weeks.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Sanchez-Espiridion B, Martin-Moreno AM, Montalban C, et al: Immunohistochemical markers for tumor associated macrophages and survival in advanced classical Hodgkin's lymphoma. Haematologica. 2012;97:1080-1084

2. Tan KL, Scott DW, Hong F, et al: Tumor-associated macrophages predict inferior outcomes in classic Hodgkin lymphoma. A correlative study from the E2496 intergroup trial. Blood. 2012;120(18):3280-3287

3. Wobser M, Roth S, Reinartz T, Rosenwald A, Goebeler M, Geissinger E: CD68 expression is a discriminative feature of indolent cutaneous CD8-positive lymphoid proliferation and distinguishes this lymphoma subtype from other CD8-positive cutaneous lymphomas. Br J Dermatol. 2015 Jun;172(6):1573-1580. doi: 10.1111/bjd.13628