Pathology of Intranodal Palisaded Myofibroblastoma
Intranodal Palisaded Myofibroblastoma is a rare benign tumour originating from smooth muscle cells and myofibroblasts.
There were two publications in 1989 which described spindle-cell tumors with dense collagen or hyaline nodules.
These lesions were exclusively noted in the inguinal region.
The first publication studied 22 cases and was titled "Palisaded myofibroblastoma, a benign mesenchymal tumor of lymph node".
The second publication was on 6 similar cases and was called Intranodal hemorrhagic spindle-cell tumor with "amianthoid" fibers.
The tumour occurs over a wide age range.
The patients present with an enlarged lymphnode, usually in the inguinal region. Though inguinal region is the commonest site of this rare tumor, but the tumor at other diverse sites have been reported.
Grossly, the Intranodal Palisaded Myofibroblastoma cut surface shows areas of hemorrhage.
The tumour is well circumscribed, with compressed lymphnode tissue at the periphery. It consists of intersecting fascicles of bland-looking spindle cells.
These are probably myofibroblasts.
A characteristic feature is the formation of stellate collagen nodules (amianthoid fibres).
The foci of collagen widely referred to as amianthoid fibers contained fibrils mostly of diameter, 50-83 nm.
Interstitial hemorrhage is often prominent. There may be hemorrhagic zone in the periphery.
Intranodal Palisaded Myofibroblastoma is positive for smooth muscle actin and cyclin D1.
It is negative for neural markers such as S100 protein, and endothelial markers such as CD34, and desmin. It shows a low proliferative index of Ki-67.
Electron microscopy demonstrates features of myofibroblasts and smooth muscle cells. Myofibroblastic tumours
In contrast to Kaposi's sarcoma, it behaves in a benign fashion and does not need any further therapy except total surgical resection of the mass.
Recently reported cases of Intranodal Palisaded Myofibroblastoma has been associated with expression of cyclin D1 and with infections from human herpes virus-8 (HHV-8) and Epstein-Barr virus.
Prognosis is excellent and surgical excision is the only needed treatment.
Intranodal palisaded myofibroblastoma with so-called amianthoid fibers: a report of two cases with a review of the literature.
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