Incidental Walthard cell nests in the intestine. Report of two cases and review of the literature.

Walthard cell nest (WCN) is a rare incidental finding in the intestine including the vermiform appendix and the mesocolon. This article describes a case of WNCs in the vermiform appendix and the mesocolon. The location in the mesocolon is reported for the first time. A review of the seven published intestinal cases including our report is presented. The lesion is seen in children, adults, and both sexes. The number of present cell nests varied between one and three per case. The diagnosis rests on histopathological examination. A potential source for histopathological diagnostic error includes a NET. The coexistence of WCNs with an appendicular neuroendocrine tumor (NET) may complicate the diagnosis. WCNs show the immunohistochemical profile of urothelial differentiation. To establish a diagnosis of WCN the absence of significant atypia, significant mitotic activity, atypical mitoses, necrosis, desmoplastic stroma, and tissue invasion must be confirmed. The lesion is a benign proliferation and once the appendectomy or colectomy has been performed, no further treatment is required.