Angiomatoid malignant fibrous histiocytoma with extensive lymphadenopathy simulating Castleman's disease.

We report the association in a 10-year-old boy of an angiomatoid malignant fibrous histiocytoma (AMFH) of the left thigh with ipsilateral inguinal, pelvic and extensive retroperitoneal lymphadenopathy, and severe systemic manifestations. These include growth retardation, fever, severe anemia, hypergammaglobinemia, and hypoalbuminemia. At ultrastructural level the tumor was characterized by an abundance of myofibroblasts, occasional histiocytes, and small vessels with marked reduplication of the basal lamina. Biopsies of the inguinal and abdominal lymph nodes showed follicular hyperplasia and massive plasmacytosis indistinguishable from Castleman's disease (giant lymph node hyperplasia) of plasma cell type. The radical surgical excision of the primary tumor in the thigh resulted in the disappearance of the abdominal lymphadenopathy and a marked reduction in size of the pelvic lymph nodes with marked decrease of the gammaglobulins, thus proving that the nodal lesions were the expression of a reactive process to the tumor rather than a coincidental independent lymphoproliferative disorder. Retroperitoneal and pelvic node dissection was performed 1 year after the radical excision of the thigh tumor because of persistent pelvic lymphadenopathy and failure of serum immunoglobulins M and A to return to normal level, with a recent peak of IgA to twofolds that of normal value. Metastatic AMFH was found in the three pelvic nodes. One month postoperatively IgA returned to near normal level whereas IgM remained slightly elevated.