Absorbable Haemostatic Artefacts as a Diagnostic Challenge in Postoperative Follow-Up After Oncological Resection in Head and Neck Tumours: Systematic Review of Current Literature and Two Case Reports

<b><i>Objectives</i>:</b> This article aims to define the clinical, radiological, and pathological characteristics of non-resorbed oxidised cellulose-induced pseudotumours to raise awareness among surgeons and radiologists, to prevent misdiagnosis, and avoid unnecessary invasive procedures and delays in adjuvant oncological treatments. <b><i>Methods</i>:</b> A systematic review of oxidised resorbable cellulose (ORC)-induced pseudotumours of the head and neck was conducted following PRISMA 2020 guidelines. Articles were retrieved from PubMed, Scopus, Cochrane, and Web of Science. Two ORC-induced pseudotumour cases from the Maxillofacial Surgery Department of Verona are also presented. <b><i>Results</i>:</b> In most cases, pseudotumours were monitored using ultrasound. Further investigations included CT, MRI, PET-CT, and scintigraphy. Ultrasound images showed stable, elongated, and non-homogeneous masses. In CT scans, pseudotumours showed a liquefied core, and none or only peripheral enhancement. In MRI, pseudotumours presented none or only peripheral enhancement, and a heterogeneous pattern in T2-weighted images. 18-FDG PET scans demonstrated an FDG-avid mass (SUV 7.5). Scintigraphy was inconclusive. Cytology indicated a granulomatous reaction without neoplastic cells. Where surgical excision was performed, a granulomatous reaction with the presence of oxidised cellulose fibres was confirmed. <b><i>Conclusions</i>:</b> Surgeons should consider artifacts from retained oxidised absorbable haemostatic material when suspecting tumour recurrence or metastasis on postoperative imaging, especially if certain features are present. Fine-needle aspiration cytology (FNAC) is a useful diagnostic tool, but surgical excision may be needed if FNAC is inconclusive or impractical. Collaboration between surgeons and radiologists is essential to avoid misdiagnosis and delays in treatment. Documenting the use and location of haemostatic material in operative reports would aid future understanding of these phenomena.