[Lymph node myofibroblastoma: report of a submandibular case with peculiar morphologic and immunohistochemical characteristics].

The Authors describe a case of intranodal myofibroblastoma presenting in the submandibular region as a firm, indolent and freely mobile rounded nodule of about 3 cm. in diameter. The nature of this uncommon benign lesion is discussed. The observed histological features are partly different from the cases originally described. A proliferation of moderately pleomorphic spindle cells, which are vimentin and muscle specific actin positive, occupies a large part of a lymph node, sharply separated from the normal tissue. The so called "amianthoid fibres" are however absent and the inflammatory cells are almost exclusively eosinophils, mainly localized at the border between the lesion and the residual lymph node. Some spindle cells also show an unexplained positivity for the S-100 protein. In addition, extranodal extension of inflammation with few spindle cells is present. Such a complex picture has many features in common with the inflammatory pseudotumor of lymph node, another benign cause of lymphadenopathy. For this reason, the Authors suggest the possibility that myofibroblastoma is not a true neoplasm, but, together with the inflammatory pseudotumor, a peculiar type or a different stage of an abnormal lymph node reactivity.