An Imitator Within: A Case of Appendiceal Neuroma Masquerading as Chronic Appendicitis

Abstract

The incidence of appendicitis, an inflammation of the appendix, has been rising significantly in many countries worldwide. Appendicitis may present in various forms, including acute or chronic inflammation, and can manifest as either uncomplicated or complicated conditions, etc. Among these conditions, chronic appendicitis is a rare type of appendiceal inflammation that is less common than acute appendicitis. In this case report, we describe a case of idiopathic appendiceal neuroma, which was initially misdiagnosed as acute gastroenteritis. Diagnosis was further supported by comprehensive laboratory testing, computed tomography and ultrasound imaging, as well as immunohistochemical staining. The patient made a full recovery following a laparoscopic appendectomy. This case highlights appendiceal neuroma as an elusive entity with atypical presentation of appendicitis and chronic histological features, emphasising the critical role of histopathology in establishing a definitive diagnosis.

Keywords: appendicitis; chronic; fibrous obliteration; gastroenteritis; neuroma.

Figure 1. CT-scan images (A, B), a picture of the appendix during surgery (C), micrographs of the biopsied appendix stained with haematoxylin and eosin (D, E), and immunohistochemical staining (F-H).

The appendix (red arrow) was identified in the coronal (A) and axial (B) views of the CT-scan image. No focal lesion or mass, no peripancreatic collection, and no streakiness of the adjacent fat were seen. Distended fluid-filled loops of small and large bowel were observed. Thickened distal ileum and caecum were noted. The stomach, small bowel and the rest of the large bowel appeared normal. No obvious bowel-related mass was observed. The appendix was noted to be about 5-6 mm in diameter, and no appendicular mass was observed. (C) Congested blood vessels were observed on the outer surface of the appendix (red arrow), and no perforation can be observed. (D) The cross-sectional view of the appendix (40x magnification) shows fibrosis and fibrofatty tissue infiltration (blue arrows). A reactive lymphoid follicle (gold arrow) was observed surrounded by diffuse lymphoid tissue. Diffuse lymphoid tissue was observed with the loss of the germinal centre (green arrow). Chronic inflammatory cell infiltration (white arrow) was observed in the inner region of a crypt. A mucosal erosion (red open arrow) was noted. Scattered neutrophils were present within the crypt epithelium and mucosa. The wall is infiltrated by mild lymphocytes. Serosa was fibrotic and had no evidence of parasites, granuloma or malignancy. (E) Under 100x magnification, a lymphoid aggregate (yellow open arrow) was observed somewhere in between the submucosa and muscularis layers of the appendix. Immunohistochemical (IHC) staining was performed to stain S-100 protein (F), chromogranin A (G), and synaptophysin (H). Micrographs F-H were captured at 40x magnification.