mart-1-antigen and Peripheral-Nervous-System-Neoplasms

Four cases of a rare melanotic variant of malignant nerve sheath tumour (MNST) in dogs are described. All four cases presented with neurological clinical signs due to multicentric, intradural, intra- and extraparenchymal neoplasms that surrounded the spinal and cranial nerves and infiltrated the adjacent spinal cord and brain. The dogs were young (3 months to 3 years of age), all were female and four different breeds were represented. Characteristic histological features were interweaving fascicles of spindle-shaped cells, sometimes with an architecture reminiscent of Antoni A and B patterns. Some spindle cells showed prominent cytoplasmic melanin pigmentation and such cells were positive by Masson-Fontana stain. Immunohistochemistry performed in three cases was positive for S100 and vimentin, strongly positive for melan A in the melanized cells and negative for glial fibrillary acidic protein and periaxin. Non-melanized cells did not express melan A. Transmission electron microscopy findings in one case were consistent with a peripheral nerve sheath tumour and demonstrated cytoplasmic pre-melanosomes and melanosomes. Melanotic variants of MNSTs are rare in animals with only a solitary report of two previous canine cases in the literature.

Topics: Animals; Dog Diseases; Dogs; Female; Immunohistochemistry; MART-1 Antigen; Microscopy, Electron; Nerve Sheath Neoplasms; Peripheral Nerves; Peripheral Nervous System Neoplasms; Spinal Cord; Vimentin

April 2004: A 53-year-old woman presented with a large club-shaped intra- and extraspinal tumor of the C6 nerve root which had intradurally grown through the enlarged C5-6 neural foramen and focally infiltrated the dura mater. Microscopy revealed a melanin-pigmented tumor with spindle-shaped and epithelioid cells and scattered psammoma bodies, a so-called psammomatous melanotic schwannoma (PMS). More than half of the patients with PMS have Carney complex, a genetically heterogeneous multiple neoplasia syndrome of autosomal-dominant inheritance, which in our patient, however, could not be detected unequivocally. Prognosis of all melanotic schwannomas (MSs) is not good with local recurrences or metastases in over 40% of cases. In our case, frequent versicular nuclei with distinct nucleoli, occasional mitoses and apoptoses and increased focal MIB-1 labeling indices prompted us to diagnose a malignant PMS. However, histologic criteria for malignancy in MSs are not clearly defined and there is no reliable histopathological indicator of malignant clinical behavior in MSs. Therefore, designation of "PMS with malignant histologic features" may be more appropriate. Since tumor recurrences and metastases im MSs may occur after more than 5 years, long-term follow-up of affected patients is required. One year after operation our patient showed no signs of tumor recurrence or metastases.

Topics: Antigens, Neoplasm; Female; Humans; Magnetic Resonance Imaging; MART-1 Antigen; Melanoma-Specific Antigens; Middle Aged; Neoplasm Proteins; Neurilemmoma; Peripheral Nervous System Neoplasms; S100 Proteins; Spinal Cord Neoplasms

A majority of desmoplastic melanomas and some of the other forms of melanomas are S-100 positive and HMB45 negative; this pattern of immunoreactivity is similar to certain nerve-derived tumors such as malignant peripheral nerve sheath tumor. In this study the immunostaining profile of HMB45-negative malignant melanomas was evaluated by a panel of antibodies against markers associated with melanoma and melanocytic differentiation, including microphthalmia transcription factor, tyrosinase, Melan-A, and MAGE-1. Immunodetection was performed on paraffin sections of 22 cases of HMB45-negative malignant melanomas (including 8 spindle cell melanomas, 8 desmoplastic melanomas, and 6 epithelioid melanomas), 8 HMB45-and S-100-positive malignant melanomas, 15 malignant peripheral nerve sheath tumors, 16 schwannomas, and 11 neurofibromas. Of eight HMB45-positive malignant melanomas, all were positive for Melan-A, tyrosinase, and melanocyte-specific transcription factor, and three were positive for MAGE-1. In the 14 HMB-45 negative, nondesmoplastic melanomas, melanocyte-specific transcription factor was positive in 9, Melan-A in 9, tyrosinase in 6, and MAGE-1 in 11. In eight desmoplastic malignant melanomas, MAGE-1 was positive in three, and all other markers were negative. The five markers tested were negative in all but two schwannomas, one with focal melanocyte-specific transcription factor and the other with tyrosinase and weak MAGE-1 reactivity. MAGE-1, melanocyte-specific transcription factor, tyrosinase, and Melan-A are useful markers in the diagnosis of malignant melanocytic lesions when HMB45 is negative. MAGE-1 may be useful in differentiating melanocytic lesions from nerve-derived lesions, but its sensitivity is relatively low. The immunostaining profile of desmoplastic malignant melanomas more closely resembles that of malignant peripheral nerve sheath tumor than that of other types of malignant melanoma. Melanocyte-specific transcription factor is not a useful marker for desmoplastic melanoma.

Topics: Antigens, Neoplasm; Biomarkers, Tumor; DNA-Binding Proteins; Humans; Immunophenotyping; MART-1 Antigen; Melanoma; Melanoma-Specific Antigens; Microphthalmia-Associated Transcription Factor; Monophenol Monooxygenase; Neoplasm Proteins; Nerve Sheath Neoplasms; Peripheral Nervous System Neoplasms; S100 Proteins; Transcription Factors