Low-grade fibromyxoid sarcoma arising within the median nerve.

We report a case of low-grade fibromyxoid sarcoma arising within the median nerve. A 31-year-old woman presented with symptoms of carpal tunnel syndrome and an enlarging mass in her right palm over 1 year. MRI demonstrated a mass associated with the right median nerve with solid and cystic components. At surgery, the mass was located within the epineurium, could be bluntly dissected from the nerve fascicles, and was suspected to be a schwannoma. A 3.4 cm, tan-pink, glistening, smooth, homogenous mass was submitted to pathology. Microscopically, the tumor was a solid and cystic circumscribed nodule with a dense fibrous pseudocapsule. The tumor cells were uniformly bland and spindle-shaped, with small, hyperchromatic oval nuclei and were embedded in an alternating fibrous and myxoid stroma with a prominent curvilinear vasculature and perivascular sclerosis. The differential diagnosis for this lesion included myxoid neurofibroma, schwannoma, soft tissue perineurioma, low-grade malignant peripheral nerve sheath tumor and low-grade fibromyxoid sarcoma. The tumor cells expressed MUC4, GLUT-1, and vimentin and were negative for S-100 protein, epithelial membrane antigen, smooth muscle actin, desmin, claudin-1, neurofilament and SOX10. Fluorescence in situ hybridization, with a break-apart probe strategy, demonstrated FUS rearrangement, consistent in this morphological context with the low-grade fibromyxoid sarcoma-associated FUS-CREB3L2 or FUS-CREB3L1 fusions. Low-grade fibromyxoid sarcoma is exceptionally rare in the peripheral nerve, with only a single previously reported case. Nonetheless, as our case illustrates, this entity must be included in the differential diagnosis of unusual intraneural mesenchymal tumors. As in all other locations, intraneural low-grade fibromyxoid sarcomas should be excised with negative margins. Patients with this disease require long-term clinical follow-up, given this tumor's propensity for very late distant metastases to the lungs and other sites.

Histiocytic sarcoma in the small intestine: a case report with flow cytometry study and review of the literature.

We describe a case of true histiocytic sarcoma (HS) with features of HS in clinical manifestation, histological presentation, and immunohistochemical panels. The flow cytometry studies were used for the diagnosis. The tumor presents in the small intestine with involvement of regional mesenteric lymph nodes of a 68-year-old female. Histological examination reveals that tumor cells are large and pleomorphic. They have vesicular chromatin and abundant eosinophilic cytoplasm. Immunohistochemical studies show the tumor cells to be positive for CD45 (LCA), CD45RO, CD4, CD68, and lysozyme; and negative for all other T-, B-, macrophage, follicular dendritic- and hematopoietic-cell markers. Proliferation rate is 5% by MIB stain. Flow cytometry studies reveal large atypical cells positive for CD4, CD14, and CD45. There are 29 cases of HS reported in the literature since 2001. All of these cases are summarized. The diagnostic methods and the possible prognostic factors are discussed. We believe that the correct diagnosis of HS is important for clinical treatment and prognostic prediction, although it is very rare.