PMC3539338_01
(a) Pathologic review of the tumor showed fibrous septa and nodular texture surrounded by lymphocytic infiltrate. Hematoxylin and eosin stain (12, 5x). (b) Detail image showing the absence of a capsular sinus. Hematoxylin and eosin stain (25x). (c) Image of excised tumor showing fibrous septa and nodular texture surrounded by lymphocytic infiltrate. Hematoxylin and eosin stain (12, 5x). (d) Detail image showing reticular appearance and atypical cytomorphology. Hematoxylin and eosin stain (100x).
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fig1
The atypia was specified by undefined cell borders, an amphophilic cytoplasm, large polygonal nuclei and several in part atypical mitoses (Figure 1(d)). The tumor nodules were partially surrounded by fibrous septa and densely vascularized by a capillary network (Figures 1(a) and 1(c)). A dense and extensive lymphatic infiltrate with no evident subcapsular sinus surrounded the spindle cell proliferation (Figure 1(b)).
(a) Melan A stain showing focal positivity. Melan A stain (200x). (b) The neoplastic cells were positive for EMA staining. EMA stain (25x). (c) Electrophoretogram of direct sequencing of the junctional region of the EWSR1-CREB1 fusion transcript, with in-frame fusion. The schematic overview shows the EWSR1 nucleotides/amino acids in black and the CREB1 nucleotides in red.
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fig2
There was focal positivity for S100 and Melan A (Figure 2(a)) leading to a presumptive diagnosis elsewhere of a melanoma metastasis. The neoplastic cells were positive for CD99 and EMA (Figure 2(b)) and to a lesser extent for CD31. Additional molecular research, performed in support of this diagnosis, showed a gene fusion mutation of EWSR1-CREB1 t(2;22)(q33;q12) (Figure 2(c)), while mutations in BRAF and NRAS genes, common in cutaneous melanoma, could not be detected.