Acute Appendicitis and Periappendicitis Revealing Squamous and Transitional Cystic and Solid Nests in Adult Patients: Metaplasia or Vestigeal Remnants?

Abstract

Squamous metaplasia of the appendix serosa is rare. We aimed to report the clinical and morphological features of 3 such cases. The patients presented with abdominal pain (n = 1 man, 2 women; age range, 29–35 years). The clinical diagnosis was appendicitis/periappendicitis (in the context of hydro/pyosalpinx). The surgical resected appendix showed several cystic and solid epithelial nests (1 mm and less) in the serosa/subserosa. Epithelial cells expressed p63, cytokeratin 5/6, as well as cytokeratins 7, 20, and CD10. Cystic and solid squamous and transitional epithelial nests of the appendix subserosa/serosa in adult patients may be revealed by acute appendicitis/ periappendicitis. The presence of such lesions, metaplastic or vestigial in nature, should be acknowledged since they can be misdiagnosed with metastatic epithelial tumor nests or they may undergo malignant change.