Intranodal Palisaded Myofibroblastoma: First Case Report in Taiwan and Review of the Literature

Intranodal palisaded myofibroblastoma (IPM) is a very rare primary mesenchymal tumor arising from the lymph nodes. Only around 70 tumors have been reported in the English literatures. Most tumors were found in adult patients and were located in inguinal lymph nodes. IPM is a benign tumor; no malignant changes nor metastases have been reported and surgical resection is sufficient for treatment. However, this tumor is easily misdiagnosed as a metastatic malignant tumor, such as Kaposi’s sarcoma, melanoma, or leiomyosarcoma. Here we report the first incidence of IPM in Taiwan. A 40-year-old male patient presented with a painless, elastic nodule in the right inguinal region that had persisted for a long period of time. Excision biopsy was performed to investigate a suspected lymphadenopathy. Microscopically, the tumor was composed of interlacing bundles of spindle cells with nuclear palisading, focal hemorrhage, hemosiderin deposition, and the presence of amianthoid fibers. The latter is characteristic of IPM. A rim of remnant lymphoid tissue was observed at the tumor border. The tumor cells were positive for smooth muscle actin and cyclin D1, but negative for desmin, CD34, S-100 and CD117 by immunohistochemical staining . The patient had no tumor recurrence 3 years after resection. Since primary mesenchymal tumors in the lymph node are rare, it is important to avoid misdiagnosis of IPM as a metastatic malignant tumor, as this can result in inappropriate treatment.