Molecular analysis of sarcoidosis lymph nodes for microorganisms: a case–control study with clinical correlates

Robinson, Lary A; Smith, Prudence; SenGupta, Dhruba J; Prentice, Jennifer L; Sandin, Ramon L

Additionally, the number of lymph nodes positive for bacterial DNA may be significantly underestimated because of the tendency of the formalin-fixation and paraffin embedding process to breakdown prokaryotic DNA. Also, over time other investigators have found degradation of the prokaryotic bacteria DNA (especially mycobacteria) with aging of the paraffin-embedded specimens. 14 Of note, the only 3 sarcoidosis lymph nodes positive for mycobacteria in our study were less than 3 years old when evaluated by PCR. Had we used fresh lymph node tissue like Drake and associates 14 who found 60% PCR positive for mycobacteria species, there may have been a much higher rate of positive bacterial DNA results (particularly mycobacteria) in our study.