Mast cells (MCs) have been identified in various tumors; however, the role of these cells in tumorigenesis remains controversial. Here, we quantified MCs in human and murine malignant pleural effusions (MPEs) and evaluated the fate and function of these cells in MPE development. Evaluation of murine MPE-competent lung and colon adenocarcinomas revealed that these tumors actively attract and subsequently degranulate MCs in the pleural space by elaborating CCL2 and osteopontin. MCs were required for effusion development, as MPEs did not form in mice lacking MCs, and pleural infusion of MCs with MPE-incompetent cells promoted MPE formation. Once homed to the pleural space, MCs released tryptase AB1 and IL-1β, which in turn induced pleural vasculature leakiness and triggered NF-κB activation in pleural tumor cells, thereby fostering pleural fluid accumulation and tumor growth. Evaluation of human effusions revealed that MCs are elevated in MPEs compared with benign effusions. Moreover, MC abundance correlated with MPE formation in a human cancer cell–induced effusion model. Treatment of mice with the c-KIT inhibitor imatinib mesylate limited effusion precipitation by mouse and human adenocarcinoma cells. Together, the results of this study indicate that MCs are required for MPE formation and suggest that MC-dependent effusion formation is therapeutically addressable.

To develop and pretest an European Organization for the Research and Treatment of Cancer Sexual Health Questionnaire (EORTC SHQ‐22) for the assessment of physical, psychological, and social aspects of sexual health (SH) in male and female cancer patients and survivors. Questionnaire construction started with creating a list of relevant SH issues based on a comprehensive literature review. Issues were subsequently evaluated for relevance and prioritization by 78 healthcare professionals (HCP) and 107 patients from 12 countries during in‐depth interviews (phase 1). Extracted issues were operationalized into items (phase 2). Phase 3 focused on pretesting the preliminary questionnaire in a cross‐cultural patient sample (n = 171) using debriefing interviews. Psychometric properties were preliminary determined using a principal component analysis and Cronbach's alpha. We derived 53 relevant SH issues from the literature. Based on HCP and patient interviews, 22 of these 53 issues were selected and operationalized into items. Testing the preliminary 22‐item short questionnaire resulted in a change of wording in five items and two communication‐related items; no items were removed. Preliminary psychometric analysis revealed a two‐factor solution and 11 single items; both scales showed good reliability indicated by a Cronbach's alpha of 0.87 (sexual satisfaction) and 0.82 (sexual pain). Cross‐cultural pretesting of the preliminary EORTC SH questionnaire has indicated excellent applicability, patient acceptance, and comprehensiveness as well as good psychometric properties. The final development phase, that is psychometric validation (phase four) including large‐scale, cross‐cultural field testing of the EORTC SHQ‐22, has commenced.