Intranodal palisaded myofibroblastoma (IPM), a benign, rare primary mesenchymal neoplasm, located in the inguinal lymph nodes, was described as “palisaded myofibroblastoma” by Weiss et al, and “intranodal hemorrhagic spindle-cell tumor with amianthoid fibers” by Suster and Rosai.［1,2］ Similar neoplasms have been previously reported as intranodal schwannoma.［1］ The age of the patients ranged between 19-70 years, and more men are affected than women.［2］ Even though most of the cases occurred in inguinal lymph nodes, the submandibular, cervical and mediastinal lymph nodes location also have been reported.［2,3］ IPM is generally characterized by proliferation of spindle cells, interstitial hemorrhage and amianthoid fibers. Metaplastic bone formation and calcification have been also reported.［3,4］ IPM has also been reported as multicentric［1］ and recurrent.［2］ The neoplasm appears to be benign. Metastases have not been reported. Local excision is adequate and curative.［5］
We report a 48-year-old woman with IPM, located in the inguinal lymph nodes. This patient underwent an operation for uterine leiomyoma ten years ago. The aim of our case report is to review the histopathological features and differential diagnosis of IPM with metastatic or primary other examples of spindle cell proliferation of lymph node.
The patient, a 48-year-old woman, was admitted (January 22, 2004) to the Department of Surgery because of a slow growing and painful mass in her left groin for 2 years. She had total abdominal hysterectomy and bilateral salpingo-oophorectomy for uterine leiomyoma ten years ago. In the examination of the patient, multiple enlarged lymph nodes were identified in her left groin. Lymph nodes did not regress with antibiotic treatment. These lymph nodes were excised to rule out lymphoma, bacterial infection or metastatic tumors. The patient was discharged (January 23, 2004) without complications and has been free of disease until March 18, 2005.
Macroscopically, the lymph nodes, 0.5-3.0 cm in diameter, were well circumscribed. Cut surface of the greatest lymph node was firm, solid, and gray-white-to-tan. The other nodes were normal in gross examination.
Lymph nodes were fixed in 10% formalin and embedded in paraffin. Five-micrometer sections were stained with hematoxylin-eosin, Van Gieson, and trichrome stains. Immunohistochemically, the sections were stained with antibody against S-100, muscle specific actin, and desmin using avidin-biotin peroxidase complex technique.
Microscopically, the abnormal lymph node was composed of variably intersecting bundles of uniform fibroblast like spindle cells with symmetrically tapered, bland fusiform nuclei and scant eosinophilic cytoplasm and hemosiderine deposits in the first tissue examples ( Fig. 1 ). Moreover, there were also multiple collections of an intensely eosinophilic collagen matrix, which were generally oval in shape (amianthoid fibers) in the second tissue examples taken to examine atypia and mitosis since the patient had been diagnosed as uterine leiomyoma previously ( Fig. 2 ). Amianthoid fibers were stained red with Van Gieson. There were no nuclear atypia and mitosis in the cells. The tumor was circumscribed by a thick collagenous capsule and beyond there was a complete rim of residual lymphoid tissue showing lymphoid follicles with reactive germinal centers ( Fig. 3 ). Tumor cells were stained positively for vimentin and smooth muscle actin, and negative for desmin and S-100. The amianthoid fibers were negative for all of the immunocytochemical markers. All of other lymph nodes were reactive nature.
Benign and malignant neoplasms of nonlymphoid cell components of lymph nodes are remarkably rare. They may have a vascular origin or arise from a variety of mesenchymal cells, including fibroblasts, histiocytes, myofibroblasts, smooth muscle cells, dentritic reticulum cells, and interdigitating reticulum cells. They are generally spindle or stalled shaped. Spindle cell tumors may invade the lymph nodes secondarily by local extension or metastasis from different locations.［6］
Lymph nodes include primary nonlymphoid tumors such as Kaposi's sarcoma in human immuno-deficiency virus-infected patients, benign melano-cytic nevi, and malignant melanoma arising in displaced intranodal nevus cells.［2,3］ Metastatic spindle cell neoplasm to lymph nodes, including both carcinomas with sarcomatoid morphology and sarcomas, are relatively more common than primary nonlymphoid neoplasms of lymph nodes. Recog-nition of IPM entity is of paramount importance in preventing its potential confusion with metastatic or other primary neoplasm.［3］
The histogenesis of IPM is incompletely understood. The cell of origin is likely the modified myofibroblast between fibroblasts and muscle cells.［5］ This is supported by the immunophenotyping, positive staining for vimentin and actin, and negative staining for desmin, as well as ultrastructurally, by the evidence of elongated cells with long nuclei and abundant filament. IPM can represent a quasineoplastic or neoplastic proliferation in a group of lymph nodes subject to a striking degree of drainage function and massive workload.［3,7,8］ Small and repeated traumas to the region can play a role in the development of IPM.［6］ Certain environmental agents or an endogenous (probably genetic) background may be responsible.［8］
IPM has been commonly reported in inguinal locations as in our case. But also have been reported in submandibular, cervical, and medias-tinal locations. Myofibroblasts have been reported as increased numbers in the inguinal lymph nodes, which may be due to the proliferation of them secondary to the increased drainage function in the inguinal lymph nodes.［3,5,8］
The tumors are solitary, painless, palpable, typically well-circumscribed, round-oval mass with firm, gray-white tissue and focal areas of hemorrhages. They are usually 0.6-5.0 cm in diameter.［6］
The tumor mass has a nodular configuration and low power examination may identify a thin, compressed rim of normal lymph node separated from the neoplasm by a thick band of sclerotic hyalinized tissue, forming a pseudo capsule. The tumor is composed of parallel, slender, spindle-shaped cells that arranged in solid sheets or crisscrossing fascicles. There is no nuclear atypia. Mitoses are rare, usually less than 2 per 50 high-power fields. Hemorrhage is a prominent feature. A characteristic feature observed in all cases is cellular stellate-shaped collagen-rich areas so-called amianthoid fibers.［6］ Our case showed similar features, but there was no mitotic figure and compressed rim of lymph node was reactive in nature.
Even if amianthoid fibers are characteristics of IPM, stellate collagen formation similar to them has been reported in malignant schwannoma, fibrous histiocytoma, epitheloid leiomyosarcoma, chondro-sarcoma, and synovial sarcoma.［2］ Amianthoid fibers may be found in degenerative and neoplastic conditions of cartilage.［8］ Collagen fiber aggregation might be secondary to trauma and anoxia due to vascular obliteration or disruption.［2］ Amianthoid fibers are stained red with Van Gieson staining. These fibers are negative for Congo red staining. Immunohistochemically, most of tumor cells are strongly positive for actin and vimentin while they give negative reactions for cytokeratin, epithelial membrane antigen, desmin, factor Ⅷ-related antigen, myelin basic protein and S-100 protein as in our case.［2］ The tumors and pseudotumors other than IPM, can be excluded clinically, histologically, and immuno-histochemically. The differential diagnosis for this lesion includes benign metastasizing leiomyoma, Kaposi's sarcoma, intranodal schwannoma, inflammatory pseudo-tumor, and metastatic disease especially leiomyosarcoma, malign melanoma, and carcinoma.［1］
There is more evident conventional appearance of the smooth muscle cells and they will be positively immunostained by smooth muscle actin, desmin, vimentin and negatively HMB-45 and in benign metastasizing leiomyoma.［9］ In our case, this lesion was particularly considered for differential diagnosis since the patient was operated for uterine leiomyoma ten years ago and only spindle cells and hemosiderine deposits were observed in the first tissue examples. These findings as amianthoid fibers, positive actin and vimentin, and negative desmin were harmonious with IPM. Kaposi's sarcoma typically shows greater nuclear pleomorphism, higher mitotic activity, and features slit-like vascular spaces and extra cellular eosinophilic bodies. Immunohistochemistry will further distinguish the cells of Kaposi's sarcoma, which are positive with vascular markers, but no smooth-muscle actin. Intranodal schwannoma includes Antoni A and Antoni B areas. Immunostaining for S-100 is positive.［2,9］
An inflammatory pseudotumor of the lymph nodes shows proliferation of spindle cells, blood vessels lined by flat endothelium, and inflammatory cell infiltrate; it differs from IPM because of its inflammatory character, being particularly rich in plasma cells.［9］ Metastatic or primary intranodal sarcoma exhibits irregular architecture, marked nuclear atypia and frequent mitoses on the contrary to IPM. A negative reaction with S-100 and HMB-45 excludes from metastatic melanoma.［5,9］
As a conclusion we underline that the diagnosis of IPM may sometimes be difficult in patients with history of benign or malignant tumor composed of spindle cells. Hence, clinical and histopathological data should be carefully reviewed and more tissue examples should be taken from the lymph nodes if necessary.
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