IMR Press / EJGO / Volume 42 / Issue 2 / DOI: 10.31083/j.ejgo.2021.02.5463
Open Access Editorial
Immunohistochemical expression of cannabinoid receptors in women’s cancers: what’s new?
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1 Department of Maternal, Child and Adult Medical and Surgical Sciences, University Hospital of Modena, 41124 Modena, Italy
2 Second Opinion Network, 41100 Modena, Italy
Eur. J. Gynaecol. Oncol. 2021, 42(2), 193–195;
Submitted: 3 January 2020 | Revised: 20 February 2020 | Accepted: 21 December 2020 | Published: 15 April 2021
Copyright: © 2021 The Authors. Published by IMR Press.
This is an open access article under the CC BY 4.0 license (

The cannabinoid receptors belong to the G protein-coupled receptor superfamily and are integral part of the endocannabinoid system. Two main types of cannabinoid receptors are known: cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2). In the last few years, great attention has been paid to the immunohistochemical evaluation of CB1 and CB2 expression in various types of tumors, including women’s cancers, for the alleged anticancer properties of cannabinoids. Today, in the modern era of precision oncology, monoclonal antibodies for the immunohistochemical evaluation of CB1 and CB2 expression are available on the market; therefore, our recommendation is to submit preliminary the formalin-fixed, paraffin-embedded, bioptic or surgical specimen of neoplastic tissue, containing at least 100 tumor cells and coming from the selected patient with no history of cannabis abuse, to predictive immunohistochemistry, before undertaking any cannabinoid-based therapeutic attempt, in association with conventional anticancer treatments or when the most advanced care is failing. The receptor expression is determined through a ‘tumor proportion score’ (TPS), which represents the percentage of viable neoplastic cells showing partial or complete membrane staining. By exploiting a methodology analogous to that applied for PD-L1 (programmed death-ligand 1) testing on cancer tissues, the specimen can be considered to have a high CB1 and/or CB2 expression if TPS 50%; a value between 1–49% corresponds to a low expression, while below 1% certifies no significant expression and, thus, no eligibility to a cannabinoid-based pharmacological approach.

Cannabinoid receptors
Cannabinoid receptor 1 (CB1)
Cannabinoid receptor 2 (CB2)
Predictive immunohistochemistry
Tumor proportion score (TPS)
Fig. 1.
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