Figure 2.

Histological features and immunophenotype of the intramuscular ALCL. (A) The biceps femoris muscle showed a tumoral and diffuse polymorphic infiltration by large lymphoid cells (magnification 100×). Inlay: Majority of the cells were small to middle sized with pleomorphic nuclei and various size of pale cytoplasm. Intermingled and less common larger cells with eccentric lobulated "horse shoe" or "kidney-shape" nuclei and an abundant cytoplasm (so called "hallmark cells") (magnification 400×). (B) Strong membranous and perinuclear dot-like positivity for CD30 (magnification 100×). (C) T-cell phenotype of ALCL demonstrated by positivity for CD7 and CD8 (D) (magnification 100×). (E) Tumor cells expressing ALK-1 protein both in the cytoplasm and nucleus indicating the classical t(2;5) translocation (magnification 200×). (F) FISH with ALK Dual Color, Break Apart Rearrangement Probe for detecting translocations affecting 2p23 ALK breakpoint region. ALK locus in its native state is seen as two immediately adjacent red and green signals. However, if a t(2;5) chromosome rearrangement has occurred as in this case, one separate red and one separate green signals can be seen (the one remaining native ALK remains as an orange/green signal) (magnification 1000×).