A 13 years old girl was admitted one year ago with unique nodular non pigmented and painless lesion 2-2, 5 cm in size on the left leg. Medical history revealed no other family members with similar lesions, slow tumor growth rate and no other associated clinical symptoms. Excisional biopsy was performed. Microscopically, we found a pseudo-nodular lesion restricted in the deep dermis without any contact with the overlying normal epidermis (). Lymphocyte rich inflamatory infiltrate was found deep in the dermis, as a border between the proliferation and normal tissue. Tumor cells were large acidophilic oval or round in shape with distinct large nuclei and proeminent nucleoli mixed with spindle cells arranged in small nests, cords and sheets separated by fibrous septae. No mitosis or necrosis was seen. There was no cytoplasmic melanin pigment in tumor cells by conventional microscopy.
Figure 1 Tumor view at low magnification .Note that tumor is restricted to the deep dermis without any contact with normal overlying epidermis. (HE staining, ×100)
Immunostaining for vimentin, S-100 protein and Melan A revealed a strong positive reaction indicating the melanocytic lineage for tumor cells (). Low proliferative index (<1%) for Ki67 was observed in neoplastic cells. By contrast with tumor cells, endothelial cells had an unusual high proliferation rate, most of tumor blood vessels exhibited between 2-4 Ki67 positive endothelial nuclei (). No positive reaction was found for D2-40, smooth muscle actin, AE1/AE3 cytokeratin, CD68 and HMB45, neither for neuro filament associated protein and neuron specific enolase in tumor cells. Also, tumor cells were negative for desmin and glial fibrilar acidic protein.Vascular markers (CD31, CD34, FVIII related antigen) positive reaction was restricted to tumor blood vessels endothelium and highlighted a rich intratumoral vascular network with highly branched pattern between neoplastic structure suggesting an intense angiogenic process (). Lymphovascular or perineural invasion were not found on studied specimens.
Figure 2 Nested and cord like arrangements of tumor cells (a, H&E, ×200). Tumor immunophenotype revealed intense positive reaction for Melan A(b) and S100 protein(c). Highly branched intratumor blood vessels (d) were CD34 positive (e, note that (more ...)
No local recurrences, other similar lesions or distant metastases were registered after one year follow up of the case.