Immunohistochemical Inflammation in Histologically Normal Appendices in Patients with Right Iliac Fossa Pain

BACKGROUND: Histologically normal appendices resected for right iliac fossa pain in children demonstrate immunohistochemical markers of inflammation. We aimed to establish if subclinical inflammation was present in histologically normal appendices resected from adults with right iliac fossa pain. METHODS: Immunohistochemistry was performed on formalin-fixed paraffin-embedded appendices for tumour necrosis factor (TNF)-α, interleukin (IL)-6, IL-2R and serotonin in four groups: Group I (n = 120): uncomplicated appendicitis, Group II (n = 118): complicated appendicitis (perforation or gangrene), Group III (n = 104): histologically normal appendices resected for right iliac fossa pain and Group IV (n = 106) appendices resected at elective colectomy. Expression was quantified using the H-scoring system. RESULTS: Median, interquartile range expression of TNF-α was increased in Groups I (5.9, 3.1–9.8), II (6.8, 3.6–12.1) and III (9.8, 6.2–15.2) when compared with Group IV (3.0, 1.4–4.7, p < 0.01). Epithelial expression of IL-6 in Groups II (44.0, 8.0–97.0) and III (71.0, 18.5–130.0) was increased when compared with Group IV (9.5, 1.0–60.2, p < 0.01). Expression of mucosal IL-2R in Groups I (47.4, 34.8–69.0), II (37.8, 25.4–60.4) and III (18.4, 10.1–34.7) was increased when compared with Group IV (2.8, 1.2–5.7, p < 0.01). Serotonin content in Groups I (3.0, 0–30.0) and II (0, 0–8.5) was decreased when compared with Groups III (49.7, 16.7–107.5) and IV (43.5, 9.5–115.8, p < 0.01). CONCLUSION: Histologically normal appendices resected from symptomatic patients exhibited increased proinflammatory cytokine expression on immunohistochemistry suggesting the presence of an inflammatory process not detected on conventional microscopy. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00268-021-06288-w.