Fig. 1

a and b: Unclassifiable high grade small blue cell tumor. Tumor cells have high nuclear to cytoplasmic ratio (N/C ratio), brisk mitotic and apoptotic activity. Multinucleated giant tumor cells are also seen. Tumor cells are focally positive for pancytokeratin. Lymphoma, neuroendocrine, melanoma, skeletal muscle, and lineage specific markers are all negative (not shown). Fluorescence in-situ hybridization for EWSR1 gene is negative. (A 100x; B 400x). c and d: Unclassifiable large eosinophilic cell tumor. Tumor cells have a moderate amount of eosinophilic cytoplasm, fine chromatin and inconspicuous nucleoli. Tumor cells are positive for CK7. Neuroendocrine, melanoma, hepatocellular, kidney, adrenal and other lineage specific markers are all negative. (C 100x; D 400x). e and f: Unclassifiable neoplasm due to scant material. Cell block preparation shows one cluster of tumor cells with nuclear pleomorphism and abundant lymphoid infiltration. Limited immunohistochemical stains were performed due to limited cellularity. Tumor cells are positive for AE1/AE3, and negative for HepPar-1, arginase, TTF-1, NKX3.1, PAX8, CK7, and CK20