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Background Melanotic schwannoma is a rare variant of schwannoma composed of melanin-producing cellswith ultrastructural features of schwann cells.The description of the course of the tumors differs somewhat, but itis generally considered as a benign lesion.We investigated the clinicopathologic features, immunophenotypes,and ultrastructural features of 13 patients with nonpsammomatous melanotic schwannoma (NPMS).Methods Tumor specimens of each patient were sectioned and stained with hematoxylin-eosin, Fontana-Masson, Prussian blue, and periodic acid-Schiff (PAS).Immunohistochemical markers such as S-100, Leu-7,HMB-45, Melan-A, CK, EMA, vimentin, GFAP, laminin, collagenⅣ and MIB-1 were detected with theEnvision immunohistochemical staining method.Four of the cases were observed by electron microscopy.Results Of the 13 patients, 8 were male and 5 female, aged from 11 to 92 years (mean, 38.6 years).Thetumor sites included the spinal nerve root (5 patients), cranial nerve (1), greater omentum (1), subcutaneoustissue (3), mesentery (1), bone (1) and mediastinum(1).Eleven patients were followed up for over2 years,with a mean of 5.9 years.One patient (9.1%) with a primary tumor in the greater omentum developed anotherprimary tumor of the same type in the subcutaneous tissue of the abdominal wall after the first operation.Localrecurrence of the tumor was seen in2 patients (18.2%).One patient (9.1%) showed the local recurrence andmetastasis.Seven patients (63.6%) showed no evidence of the recurrence or metastasis.Grossly, all tumorswere well-circumscribed and the gross findings were suggestive of melanin-containing tumors.The tumor wascomposed of spindled and epithelioid cells with abundant intracytoplasmic melanin pigments.Nuclei were roundand contained delicate, evenly distributed chromatins as well as small, distinct nucleoli.In some areas, thenucleoli were large and prominent.Rare mitoses were seen in mostlesions exceptthe larger omentumlesion.Thepigment was shown to be positive for the Fontana-Masson and negative for Prussian blue and PAS.Immunohistochemical staining for S-100, Leu-7, HMB-45, Melan-A, and vimentin were strongly positive.Linear immunoreactions of both laminin and collagenⅣ was detected in all patients.Ultrastructurally, numerouselongated tumor-cell processes, duplicated basement membrane and melanosomes were observed in alldevelopmental stages.Conclusions Histologically, melanotic schwannoma is a rare variant of schwannoma composed of melanin-producing cells with ultrastructural features ofschwann cells.Distinguishing between this tumor andmalignant melanoma is of paramount importance inplanning of management. Immunohistochemically,combined use of laminin and collagenⅣ is valuablein distinguishing melanotic schwannoma frommalignant melanoma. Wide local resection andadditional radiotherapy should be advocated.Furtherstudies including cytogenetic or molecular biology arestill required to better delineate melanoticschwannoma from malignant melanoma. Appropriate long-term follow-up is needed for all melanoticschwannomas.
Background Melanotic schwannoma is a rare variant of schwannoma composed of melanin-producing cells with ultrastructural features of schwann cells.The description of the course of the tumors differs somewhat, but itis generally considered as a benign lesion. We investigated the clinicopathologic features, immunophenotypes, and ultrastructural features of 13 patients with nonpsammomatous melanotic schwannoma (NPMS). Methods Tumor specimens of each patient were sectioned and stained with hematoxylin-eosin, Fontana-Masson, Prussian blue, and periodic acid-Schiff 100, Leu-7, HMB-45, Melan-A, CK, EMA, vimentin, GFAP, laminin, collagen IV and MIB-1 were detected with theEnvision immunohistochemical staining method. Source of the cases were observed by electron microscopy. Results of the 13 patients, 8 were male and 5 female, aged from 11 to 92 years (mean, 38.6 years). The sites include the spinal nerve root (5 patients), cranial nerve (1), greater ome (1), bone (1) and mediastinum (1). Eleven patients were followed up for over 2 years, with a mean of 5.9 years. One patient (9.1%) with a primary tumor in the greater omentum developed another primary tumor of the same type in the subcutaneous tissue of the abdominal wall after the first operation. Local recurrence of the tumor was in 2 patients (18.2%). One patient (9.1%) showed the local recurrence and mettastasis. Seven patients (63.6%) showed no evidence of the recurrence or metastasis. Gross, all tumorswere well-circumscribed and the gross findings were suggestive of melanin-containing tumors. The tumor was composed of spindled and epithelioid cells with abundant intracytoplasmic melanin pigments. Nuclei were round and very evenly.Rare mitoses were seen in mostlesions exceptthe larger omentumlesion.Thepigment was shown to be positive for the Fontana-Masson and negative for Prussian blue and PAS. Immunohistochemical staining for S-100, Leu-7, HMB-45, Melan-A, and vimentin were strongly positive. Linear immunoreactions of both laminin and collagen IV was detected in all Patients. Ultrastructurally, numerouselongated tumor-cell processes, duplicated basement membrane and melanosomes were observed in all developmental stages. Conclusions Histologically, melanotic schwannoma is a rare variant of schwannoma composed of melanin-producing cells with ultrastructural features of schwann cells. Distinguishing between this tumor and malignant melanoma is of paramount importance in planning of management. Immunohistochemically, combined use of laminin and collagen IV is valuablein distinguishing melanotic schwannoma from malignant melanoma. Wide local resection andadditional radiotherapy should be advocated. Furtherstudies including cytogenetic or molecular biology arestill required to better delineate melanoticschwannoma from mali Appropriate long-term follow-up is needed for all melanoticschwannomas.