Pathologic Features of Miscellaneous Foregut Malignancies.

In addition to tumors arising from the primary mucosal epithelium, the foregut is host to a variety of non-epithelial precursor cells which may give rise to neoplasms of neuroendocrine, mesenchymal, and hematolymphoid lineages. Many of these lesions also occur outside of the gastrointestinal tract, such as the extranodal lymphomas and many of the sarcomas, and in many cases share the features of their non-alimentary counterparts. This heterogeneous collection of malignancies features a wide spectrum of clinical presentations, morphologic and histopathologic features, genetic underpinnings, and treatment considerations. Although encountered less frequently than primary carcinomas, it is important to correctly recognize and classify these lesions to effectively manage and prognosticate the patients in which they occur. In this chapter, we focus on the clinical, morphologic, and genetic features of the primary esophageal and gastric neoplasms of neuroendocrine, mesenchymal, and lymphoid origin.