After trimming of the 72 FFPET samples of NPC blocks obtained, 5 [micro]m sections of the tissue were taken using a microtome.
These figures are similar to those reported in Greece, where among 63 FFPET samples of NPC examined using PCR, EBV specific sequence was amplified in 20 (32%) and HPV in 12 (19%) of the samples .
In USA, among 30 FFPET samples of NPC studied using the ligation-dependent polymerase chain reaction (LD-PCR), 2 samples were coinfected with HPV and EBV .
Although some studies had no significant association to both EBV and HPV using FFPET samples , most studies using fresh NPC samples in Africa and elsewhere have shown a high level of association between NPC cases and EBV, but not HPV [7, 21, 28].
 Nonstandard abbreviations: EGFR, epidermal growth factor receptor; TKI, tyrosine kinase inhibitor; pDHPLC, partially denaturing HPLC; FFPET
, formalin-fixed, paraffin-embedded tissue.
Histology laboratory accession logs were used to secure hematoxylin-eosin-stained diagnostic tissue glass slides, FFPET block accession numbers, and dates.
The stored FFPET blocks were small without supporting cassettes, and they could not be accurately matched to the original diagnostic hematoxylin-eosin-stained tissue section because the cut surface on the block was lost when the block was re-embedded.
Immunohistochemistry markers among the 47 cases of BL and 7 cases of B-cell lymphoma, unclassifiable, varied in intensity and integrity of antigen by FFPET block age (1993-1999 versus 2000-2007; Table 1) and likely individually by the length of exposure to formalin (Figure 2, A through L).