Fine Needle Aspiration Cytology of a Postoperative Foreign Body Reaction Mimicking Peritoneal Metastasis From Colon Adenocarcinoma

INTRODUCTION: Fine needle aspiration cytology (FNAC) is a very useful tool in the management of oncological patients. It is a straightforward and quick diagnostic tool, and it can also obtain material for molecular studies that can help guide therapy. However, FNAC is not always performed when radiological studies seem conclusive. We herein report a peculiar case in which FNAC diagnosis completely changed the management of a patient. PATIENTS AND METHODS: A 75-year-old man underwent laparoscopic surgical resection of TNM stage I low-grade intestinal adenocarcinoma. A follow-up CT scan 1 year after surgery revealed multiple peritoneal nodules in the left flank, with an increased FDG uptake in the PET-CT. Radiological diagnosis was peritoneal seeding of carcinoma. FNAC was performed to confirm diagnosis, obtaining a blue material. The smears revealed a large number of histocytes engulfing a dark blue material with no tumour cells. Radiological follow-up was decided and 2 and a half years after diagnosis, the nodules have remained stable and the FDG uptake has steadily decreased over time. DISCUSSION: Foreign-body reaction against sutures and meshes employed in abdominal surgery has been widely analysed in experimental models. Lymphocytes and histiocytes are the main inflammatory cells responsible for this reaction. In the literature there are few reports of foreign-body reaction mimicking peritoneal seeding of carcinomas, and all of them were diagnosed with a biopsy of suspicious nodules. A thorough review of the literature has not revealed any similar case in which FNAC allowed diagnosis of foreign body reaction avoiding the need of surgical exploration and unnecessary systemic therapy. CONCLUSION: We herein report a unique case in which FNAC led to the correct diagnosis of a foreign body reaction, avoiding aggressive measures in an oncologic patient.