|Year : 2013 | Volume
| Issue : 2 | Page : 295-298
Intranodal palisaded myofibroblastoma: A case report and an update on etiopathogenesis and differential diagnosis
Nandyala Hariharanadha Sarma1, Katepogu Sateesh Arora1, Kalyanadurgam Pujari Varalaxmi2
1 Department of Pathology, Rural Development Trust Hospital, Bathalapalle, Andhra Pradesh, India
2 Department of Pathology, Government Medical College, Anantapur, Andhra Pradesh, India
|Date of Web Publication||13-Jun-2013|
Nandyala Hariharanadha Sarma
Department of Pathology, Rural Development Trust Hospital, Bathalapalle - 515 661, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Intra-nodal palisaded myofibroblastoma (IPM) is a rare benign lymph node mesenchymal tumor. It presents as a slow growing, painless nodular mass confined mostly to the inguinal area. Histologically, it shows palisading spindle cells, hemorrhages, hemosiderin laden macrophages, and amianthoid fibers, almost totally replacing the lymph node. Recent genetic evidence supports viral etiology. A case of IPM occurring in a 25-year-old woman is presented and the differential diagnosis of this lesion is discussed. IPM occurs between 4 th and 6 th decade of life, male to female ratio is 2:1 and the inguinal region is the commonest location. Origin of this tumor is from myofibroblasts or smooth muscle fibers. Though benign, morphologically it can be confused with malignant tumors like Kaposi's sarcoma, melanoma, and leiomyosarcoma. Prognosis is excellent and surgical excision is the only needed treatment. There are no reports of malignant transformation though an occasional case has recurred.
Keywords: Amianthoid fibers, intranodal, lymph node, myofibroblastoma
|How to cite this article:|
Sarma NH, Arora KS, Varalaxmi KP. Intranodal palisaded myofibroblastoma: A case report and an update on etiopathogenesis and differential diagnosis. J Can Res Ther 2013;9:295-8
|How to cite this URL:|
Sarma NH, Arora KS, Varalaxmi KP. Intranodal palisaded myofibroblastoma: A case report and an update on etiopathogenesis and differential diagnosis. J Can Res Ther [serial online] 2013 [cited 2019 Dec 16];9:295-8. Available from: http://www.cancerjournal.net/text.asp?2013/9/2/295/113395
| > Introduction|| |
Intra-nodal palisaded myofibroblastoma (IPM) is a rare benign mesenchymal tumor arising possibly from the myofibroblast or smooth muscle fibers present in the lymph node. Until 1989 this tumor was diagnosed as intra-nodal schwannoma or leiomyoma.  Weiss et al.  proposed the name palisaded myofibroblastoma. The synonyms for this lesion are intra-nodal hemorrhagic spindle cell tumor with amianthoid fibers  and solitary spindle cell tumor with myoid differentiation of the lymph node.  The term "INTRANODAL" was added afterwards to call this lesion as "IPM."  Its morphology can be confused with a variety of malignant mesenchymal tumors emphasizing the importance of correct diagnosis of this tumor. Possible viral etiology is gaining ground. It behaves like a benign tumor and surgical excision is sufficient for treatment. There has been no malignant transformation or metastasis by this tumor, though an occasional case has recurred.
| > Case Report|| |
A 25-year-old woman presented with a gradually increasing painless swelling in the left groin of 3 years duration. Physical examination revealed a single, painless, firm, mobile mass of size 2 × 3 cm. No other significant findings were noticed. Clinical diagnosis of metastatic sarcoma in the groin was made. Fine needle aspiration cytology (FNAC) of the swelling was reported as possible benign soft tissue tumor.
The swelling was excised for confirmatory diagnosis and further management. The patient was discharged without complications and is free of the disease so far.
The specimen received was a well-circumscribed nodular greyish brown firm mass of size 2 × 3 × 4 cm. Cut surface was greyish brown. Histology of the representative areas revealed a tumor replacing the lymph node almost totally. Remnant lymphnode was seen at the periphery [Figure 1]. The tumor consisted of bland spindle cells arranged in whorls or in fascicles. Vague nuclear palisading resembling Antoni A areas were seen at places. Small, stellate, round, or irregular eosinophilic acellular fibrillary structures were seen scattered throughout the tumor [Figure 2]. Extensive areas of fresh and old hemorrhages with hemosiderin laden macrophages were seen within the tumor [Figure 3]. Occasional normal mitoses were seen.
|Figure 1: Low power view of the lesion showing remnant lymphnode at the top and the tumor below [H and E, × 4]|
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|Figure 2: High power view of the tumor showing fascicles of spindleshaped cells with stellate or round collagenous areas-so called amianthoid fibers. Focal calcification of these fibers is noted [H and E, × 20]|
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|Figure 3: High power view of the tumor showing focus of hemorrhage and hemosiderin laden macrophages [H and E, × 20]|
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Immunohistochemistry revealed positivity for smooth muscle actin (SMA) [Figure 4] and vimentin [Figure 5] and negative for S-100 protein and desmin [Figure 6]. Histological diagnosis of IPM was made because of the typical clinical presentation, morphology, and immunohistochemistry profile.
|Figure 4: Medium power view of positive immunohistochemistry stain for smooth muscle actin × 10|
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|Figure 5: Medium power view of positive immunohistochemistry stain for vimentin × 10|
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|Figure 6: Medium power view of negative immunohistochemistry stain for desmin × 10|
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| > Discussion|| |
IPM is a rare benign mesenchymal tumor of the lymph node, possibly derived from myofibroblasts or smooth muscle fibers.  Though inguinal lymph node is the most common location, involvement of mediastinum, submandibular and cervical lymph nodes,  and retroperitoneum  have been reported.
IPM as a disease entity was established in 1989. Before that this entity was considered as primary or secondary neurilemmoma, leiomyoma, or malignant Schwannoma of the lymph node.  Weiss and collegues proposed the name palisaded myofibroblastoma. The term "INTRANODAL" was added afterwards to call this "IPM." ,
IPM has been reported in ages between 25 and 78 years. There is only one case seen in an infant.  IPM presents as a solitary asymptomatic painless nodular mass in the inguinal region. Men are more commonly affected than women. The tumor is well capsulated, usually seen deep in the groin below the inguinal ligament and involves a single lymph node without infiltrating the overlying skin. 
Gross features include grey white tumor with multifocal hemorrhagic areas. Microscopically, the tumor has a nodular configuration with fascicles of spindle cells. The nuclei may display palisading pattern. Nuclear atypia is absent and mitoses are rare.
The characteristic feature seen in all cases is the presence of mats of eosinophilic material forming bands of stellate or circular profiles.  This material called as amianthoid fibers is considered to represent degenerated or crystalline collagen.  Scattered foci of hemorrhages and extravasated red blood cells in between the spindle cells are seen.
The histogenesis is still not completely understood. The cell of origin is most likely to be the myofibroblast or smooth muscle cell of the lymph node blood vessels.  Positive staining for vimentin and actin and negative staining for desmin by immunohistochemistry (IHC) supports this notion.
Electron microscopy shows irregular contours of the nucleus and occasional intra-nuclear pseudoinclusions. Cytoplasm shows focal densities believed to be smooth muscle myofilaments.
There is a proven association between Epstein-Barr virus and human herpes virus 8.  In addition some cases of IPM have shown overexpression of cyclin D1. 
It is suggested that viral oncogenesis might be involved in the development of these lesions and possibly cyclin D1 overexpression may independently influence the spindle cells as growth factor. 
Nature of amianthoid fibers has been intriguing. Studies indicates that the center of these fibers is composed of type I collagen whereas the periphery is made up of Type III collagen. Electron microscopy also confirms that amianthoid fiber is a collagen fiber and not an amianthoid fiber. This fiber has smaller width than amianthoid fiber ranging from 80 to 150 nm versus 280 to 1000 nm. 
So far 70 cases are reported in the literature, 65 cases including our present case involved inguinal region, 4 cases submandibular region, and 1 case retroperitoneum. Inguinal lymph nodes are preferably involved possibly because of increased number of myofibroblasts secondary to increased drainage function. ,,
IPM has to be differentiated from benign lesions like leiomyoma, intranodal schwannoma, inflammatory pseudotumor, and metastatic lesions in lymph node like carcinoma, melanoma, Kaposi's sarcoma, and leiomyosarcoma.
Leiomyoma shows typical morphology and IHC positive actin, desmin and vimentin, and negative human melanoma black [HMB]-45. Schwannoma will have typical Antoni A and B areas. S-100 is positive and actin, desmin, and vimentin are negative by IHC. Inflammatory pseudo-tumor differs by its inflammatory morphology which is not a feature of IPM.
Metastatic or primary sarcomas in the lymph node show features of sarcoma-like nuclear atypia and increased mitotic activity. Melanoma can be excluded by negative HMB-45 and S-100 protein by IHC. Kaposi's sarcoma shows typical slit-like vascular spaces, extracellular eosinophilic bodies, high mitoses, and nuclear pleomorphism. Amianthoid fibers are not a feature of Kaposi's sarcoma. Positive CD34 and negative actin by IHC helps to differentiate Kaposi's sarcoma.
Diagnosis of IPM is important since potential confusion with primary or metastatic mesenchymal neoplasms in the lymph nodes can be avoided. Since IPM mostly presents as inguinal swelling, one should keep IPM in the FNAC diagnosis for inguinal swelling. Features like moderate spindle cell lesion without nuclear atypia, fibrillary stroma, and presence of hemosiderin granules can favor IPM in FNAC.
Better understanding of IPM will help in proper diagnosis and management because IPM is a benign lesion with very low or negligible rate of recurrence. We conclude with the emphasis that IPM should be kept in mind for a swelling in the inguinal lymph node.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]