Benign and malignant neoplasms of nonlymphoid cell components of lymph nodes are remarkably rare. They may have a vascular origin (see Part IX) or arise from a variety of mesenchymal cells, including fibroblasts, histiocytes, myofibroblasts, smooth muscle cells, dendritic reticulum cells, and interdigitating reticulum cells. These cells are normal components of the supporting framework of lymph nodes and other hematolymphoid organs. They are generally spindle-shaped or stellate. Their functions are diverse. Some cells are simply structural, whereas others are actively involved in immune processes. Spindle cell tumors may also involve the lymph nodes secondarily by local extension or metastasis from different locations in the soft tissues. Neoplasms arising from accessory cells, histiocytic sarcoma (see Chapter 77) and dendritic cell neoplasms (see Chapter 78) have been previously described. This part describes spindle-shaped primary proliferations of lymph nodes arising from cells with a supportive function and includes inflammatory pseudotumor and palisaded myofibroblastoma.