Obliteration of the appendiceal lumen by spindle cells in a collagenous and myxoid backdrop is found in about one third of excised appendices. The tip of the appendix is typically affected, but the entire appendix may be involved. This process may be confined to the mucosa (called intramucosal variant), or it may replace the entire lumen and underlying crypts. Immunohistochemical staining discloses S100 protein and neuron-specific, enolase-reactive spindle cells (intermingled Schwann cells and axons), and scattered endocrine cells. These phenomena are believed to be overall proliferative, with attendant phases of growth, involution, and finally fibrosis.^[1]