Intranodal palisaded myofibroblastoma

Intranodal palisaded myofibroblastoma (IPM), also known as intranodal hemorrhagic spindle-cell tumor with amianthoid fibers, is a rare, benign soft tissue tumor that typically arises within the lymph nodes. This neoplasm is characterized by the presence of spindle-shaped myofibroblasts, which are cells that play a key role in wound healing and are capable of contraction, similar to smooth muscle cells. The term "palisaded" refers to the arrangement of these cells in a pattern reminiscent of a palisade, while "amianthoid" fibers are thick, collagenous fibers found within the tumor, resembling asbestos fibers in appearance.

Etiology and Pathogenesis

The exact cause of IPM remains unknown. It is thought to arise from the myofibroblasts within the lymph node stroma. These cells can proliferate in response to various stimuli, possibly including trauma or inflammation, although no direct link has been established. The development of amianthoid fibers is considered a degenerative change, but its precise role in the pathogenesis of IPM is not fully understood.

Clinical Presentation

Patients with IPM typically present with a painless, slow-growing mass in the lymph nodes, most commonly located in the head and neck region, including the cervical lymph nodes. However, cases have been reported in other areas, such as the inguinal lymph nodes. The tumor affects adults predominantly, with no clear gender predilection.

Diagnosis

The diagnosis of IPM is primarily based on histopathological examination of the tumor. Imaging studies, such as ultrasound or computed tomography (CT) scans, may be used to assess the size and location of the mass but are not diagnostic. Histologically, IPM is characterized by spindle-shaped myofibroblasts arranged in a palisaded pattern, with interspersed amianthoid fibers. Immunohistochemistry may show positivity for smooth muscle actin (SMA), indicating the myofibroblastic nature of the cells.

Treatment and Prognosis

As IPM is a benign tumor, surgical excision is generally considered curative. There is a low risk of recurrence, especially if the tumor is completely removed. The prognosis for patients with IPM is excellent, with no known cases of malignant transformation or metastasis.

Epidemiology

IPM is a rare entity, with only a limited number of cases reported in the medical literature. Due to its rarity, the exact incidence and prevalence of the tumor are not known.

Conclusion

Intranodal palisaded myofibroblastoma is a rare, benign soft tissue tumor of the lymph nodes, characterized by the presence of spindle-shaped myofibroblasts and amianthoid fibers. The tumor has an excellent prognosis following surgical excision, with minimal risk of recurrence. Further research is needed to elucidate the etiology and pathogenesis of this unusual neoplasm.