Case 7: synchronous FL and histiocytic sarcoma with dendritic cell differentiation. (A) A mass in the tongue and neck showed both FL, grade 1, and H/DC sarcoma. The FL was associated with lingual lymphoid tissue (arrowheads), while the H/DC neoplasm was associated with the epithelium (arrows). Magnification ×20. (B) The FL was positive for CD20, CD10, and Bcl2. Magnification ×200. (C) The H/DC was positive for CD163 and focally for CD1a, as well as CD68 and S100 (not shown). There was no evidence of infiltrating FL cells, as shown in the CD20 stain. Magnification ×400. (D) The H/DC neoplasm showed fusion of the BCL2 and IGH signals (arrows), consistent with presence of the t(14;18), using dual-fusion FISH (D-FISH) probes. A control sample shows no fusion. Magnification ×1250.