Malignancy Recorded Among Secondary Diagnoses and In-Hospital Mortality in Patients Hospitalized with Chronic Ulcers: A Nationwide Romanian Patient-Level Cohort Study

Background/Objectives: Chronic ulcers are common among older and multimorbid hospitalized patients and may reflect systemic vulnerability beyond the local wound condition. Malignancy recorded among secondary diagnoses may identify patients with reduced physiological reserve and increased inpatient risk, but its prognostic significance in hospitalized chronic ulcer populations remains insufficiently characterized. This study aimed to evaluate whether malignancy coded among secondary diagnoses was associated with in-hospital mortality among adults hospitalized with chronic ulcers. Methods: This nationwide retrospective cohort study used anonymized Romanian public-hospital discharge data for adults aged ≥18 years hospitalized with chronic ulcers between 1 January 2017 and 31 December 2022. The index-episode cohort included 69,349 patients generating 116,264 hospitalizations. Exposure was defined as at least one ICD-10 C00–C97 malignant neoplasm code recorded among secondary diagnoses in the relevant analytical hospitalization. The primary outcome was in-hospital mortality. Crude and adjusted odds ratios were estimated using logistic regression models. Results: Overall, 1837 patients had C00–C97 codes recorded among secondary diagnoses, with 73 deaths. In-hospital mortality was 3.97% among exposed patients and 1.78% among unexposed patients, corresponding to a crude odds ratio of 2.28 (95% CI 1.79–2.90). After adjustment for age group, sex, admission type, chronic ulcer category, and hospitalization pattern, malignancy recorded among secondary diagnoses remained associated with mortality (adjusted OR 1.87, 95% CI 1.42–2.45; p < 0.001). Additional adjustment for the number of non-malignant secondary diagnoses yielded similar results (adjusted OR 1.88, 95% CI 1.42–2.47; p < 0.001). Conclusions: Malignancy coded among secondary diagnoses may serve as a pragmatic administrative marker of increased in-hospital mortality risk among patients hospitalized with chronic ulcers. However, residual confounding and the absence of cancer-stage information limit causal interpretation.