Miscellaneous tumours of the appendix

Fig. 5.19 Burkitt lymphoma of appendix.

Neuromas are common in the appendix. The most frequent manifestation is the axial neuroma, which causes fibrous obliteration of the appendiceal lumen. Occasionally, neuromas may be found in the mucosa or submucosa without luminal obliteration {1423, 251, 1818}. Appendiceal neuromas may be reactive lesions. Histologically, they consist of a myxoid and collagenous background within which a variety of cells is present, including nerve fibres, spindle cells that immunoexpress S-100 protein, endocrine cells, mast cells and eosinophils. In this context, the presence of endocrine cells should not be mistaken for carci-noid tumour. However, it has been suggested that some carcinoids of the appendix might develop in the same setting as appendiceal neuroma. {251}.

Stromal tumours may affect the appendix on rare occasions; they have generally been described in the literature as being of smooth muscle type {324, 865}.

Kaposi sarcoma may be found in the appendix as part of the acquired immunodeficiency syndrome {406}. Rarely, it occurs in individuals without evidence of HIV infection {295}.

Malignant lymphomas involve the appendix usually as part of more general intestinal spread. Lymphomas presenting as primary disease of the appendix are rare; some are of Burkitt type {1295, 1761}.

Secondary tumours are unusual in the appendix. Primary sites include carcinomas of the gastrointestinal and urogenital tract, breast, lung, and gallbladder. Metastatic thymoma and melanoma have also been reported {130, 98, 570, 607, 1051, 1407, 1615, 1822, 2129}. A common pattern is serosal involvement, presumably due to transcoelomic spread.

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