Metastasis to the breast from an adenocarcinoma of the lung with extensive micropapillary component: a case report and review of the literature

Intranodal palisaded myofibroblastoma (IPM) is a benign mesenchymal neoplasm originating from smooth muscle cells and myofibroblasts. It is characterized by spindle cells, amianthoid fibers, and by the proliferation of hemosiderin-containing histiocytes in the lymph node. A nodular lesion was excised from the inguinal region of an 80-year-old male patient. Macroscopic examination of a section of the lesion demonstrated a solid appearance with hemorrhagic areas. Microscopic examination revealed spindle cell proliferation, amianthoid fibers, hemosiderin pigment, and extravasated erythrocytes. Nuclei of the spindle cells displayed a palisaded appearance. Compressed lymphoid tissue was observed around the lesion. With Masson's trichrome, spindle cells stained as smooth muscle, whereas collagen staining was observed in homogeneous eosinophilic accumulations. Neoplastic cells were identified by the presence of vimentin and SMA. The Ki67 index was less than 1%. In light of these results, the case was diagnosed as "intranodal palisaded myofibroblastoma." IPM is an uncommon neoplasm originating from the stromal component of the lymph node. Although IPM is benign, it is frequently confused with metastatic lesions.