Pleural involvement in pseudomyxoma peritonei (PMP) is an exceptional event, with an estimated incidence of approximately 5.4% of cases [1]. Prognosis is poor, with a reported median survival of 55 months in patients with pleural extension [1]. While hyperthermic intraperitoneal chemotherapy (HIPEC) is the standard of care for peritoneal disease [2], optimal management of pleural involvement remains unclear. Hyperthermic intrathoracic chemotherapy (HITHOC) has shown promising results in other malignancies such as mesothelioma and thymoma [3,4], but experience in PMP is limited, and terminology across reports varies (e.g., HITHOC, intrathoracic chemoperfusion, combined abdominal–thoracic approaches) [5–8]. To our knowledge, this represents one of the few reported cases in Spain of HITHOC for PMP with pleural involvement.

A 73-year-old woman with a history of low-grade PMP diagnosed in 2017 had previously undergone multiple surgical procedures and HIPEC. In 2025, she presented with progressive dyspnea. Computed tomography (CT) revealed diffuse right pleural thickening with multiple nodules (Fig. 1). Positron emission tomography (PET-CT) demonstrated pleural hypermetabolism without evidence of peritoneal recurrence. Given disease progression and good performance status, a multidisciplinary team recommended surgical management including pleurectomy/decortication and HITHOC.

Fig. 1.

Preoperative chest CT scan (axial view) showing diffuse right pleural thickening with multiple enhancing nodules, consistent with pleural carcinomatosis.

On October 23, 2025, a right posterolateral thoracotomy was performed. Extensive extrapleural pleurectomy/decortication was carried out, including visceral pleural dissection and atypical segmentectomy of the lower lobe due to parenchymal infiltration. Total operative time was 8.5h.

HITHOC was subsequently performed using the Performer 3 system. Four catheters (two apical and two basal) were placed, and the thoracotomy was closed hermetically. A total perfusion volume of 2.7L of saline solution (including circuit volume) was circulated with cisplatin at a dose of 100mg/m2 (173mg) for 90min at 42°C. Nephroprotection was provided with sodium thiosulfate (4g/m2 bolus followed by 12g/m2 continuous infusion over 6h), based on evidence demonstrating reduced renal toxicity [9].

Postoperatively, the patient was admitted to the post-anesthesia care unit for 48h, remaining hemodynamically stable with preserved renal function (baseline creatinine 0.64mg/dL, peak 0.86mg/dL on postoperative day 2). Chest drains were removed on postoperative days 4 and 10. Prolonged pleural drainage has been described following intrathoracic hyperthermic perfusion and may relate more to the thoracic procedure than to concomitant HIPEC [10]. The patient was discharged on postoperative day 10 without complications (Clavien–Dindo grade 0). Histopathological analysis confirmed high-grade mucinous carcinoma consistent with PMP (Fig. 2).

Fig. 2.

Histopathological findings. (A) Low-power view (hematoxylin–eosin stain, ×6.1) showing abundant extracellular mucin pools dissecting fibrous tissue, characteristic of pseudomyxoma peritonei.

Pleural involvement in PMP represents a significant therapeutic challenge. HITHOC enables delivery of high local concentrations of chemotherapy with limited systemic toxicity. Cisplatin is commonly used due to its proven efficacy in peritoneal disease and favorable penetration into the pleural cavity. The main limitation is nephrotoxicity, which can be mitigated with established nephroprotection protocols [9]. Biosecurity considerations are also relevant, as approximately 59% of cisplatin is excreted within the first 48hours, necessitating strict safety measures during this period [11].

This case supports the feasibility and safety of HITHOC as a locoregional treatment strategy in selected patients with pleural involvement from PMP, achieving favorable perioperative outcomes.