Abstract
ABSTRACT
Introduction
Mycobacteria are typically identified using the acid‐fast staining technique. Prior reports have observed cross‐reactivity of
Treponema pallidum
immunohistochemistry (IHC) with
Mycobacterium
species, particularly
Mycobacterium leprae
. Further characterization of this cross‐reactivity is needed across a broader range of
Mycobacterium
species, including its extent, strength, and quality.
Materials and Methods
A retrospective review was conducted to identify all cases of mycobacterial infection at a single institution. Cases with available histopathologic slides were included. Cases in which mycobacteria were not identified on histologic examination were excluded.
T. pallidum
IHC was performed for each case that met inclusion criteria, and staining patterns were recorded.
Results
Of the 55 cases of mycobacterial infection identified, a total of 19 cases met the inclusion criteria: 10 cases of
M. leprae
, 6 cases of
M. chelonae
, 2 cases of
M. tuberculosis
, and 1 case of
M. avium
. IHC for
T. pallidum
showed cross‐reactivity in all 10
M. leprae
cases
(100%), 3 of 6
M. chelonae
cases (50%), 1 of 2
M. tuberculosis
cases (50%), and no staining in the single
M. avium
case. Cases of
M. leprae
and
M. chelonae
showed a consistent strong granular and clumped staining pattern.
Conclusions
This study demonstrates that
T. pallidum
IHC can highlight diverse
Mycobacterium
species, a cross‐reactivity that pathologists should recognize to avoid false‐positive interpretations. In the appropriate clinical context, this cross‐reactivity may be utilized to further support the diagnosis of leprosy, given the consistently strong staining observed with
M. leprae
.