HISTOLOGIC PARAMETERS PREDICTIVE OF MYCOBACTERIAL INFECTION

Tissue specimens from a wide variety of anatomic locations are frequen tly examined for mycobacteria using a combination of cultures and spec ial stains. Auramine-rhodamine (AR) staining is a sensitive method for detecting acid-fast bacilli (AFB) in tissue sections. We reviewed 85 AR-positive and 275 randomly selected AR-negative biopsy specimens col lected during the past 2 years at the Mayo Clinic, Rochester, Minn. Pa thologic diagnoses and culture results were also reviewed. Biopsy spec imens containing necrotizing granulomas yielded the highest positivity rate for AFB (61 [47.7%]), followed by nonnecrotizing granulomas (14 [17.7%]). Poorly formed granulomas (5 [16.1%]) and acute inflammation (5 [15.6%]) were less frequently positive. Cases with fibrotic or hyal inized granulomas, nonspecific chronic inflammation, nonspecific react ive or reparative changes, no significant histologic abnormality, or m alignancy failed to disclose AFB. These specimens, which were consiste ntly negative for AFB, were responsible for 25% of the samples submitt ed. Of the 360 tissue specimens submitted, 166 had a corresponding myc obacterial culture. Mycobacteria were cultured only from the biopsy sp ecimens that contained necrotizing granulomas (38.2%), nonnecrotizing granulomas (32.4%), poorly formed granulomas (30.0%), or acute inflamm ation (15.8%). Tissues with fibrotic or hyalinized granulomas, nonspec ific chronic inflammation, nonspecific reactive or reparative changes, no significant histologic abnormality, or malignancy failed to yield positive cultures. These data suggest that biopsy specimens with these latter diagnoses are inappropriate specimens for mycobacterial cultur e or AR staining.