TLiberculosisof the Thymus*
j Mark
FitzGerald,
M.B.;t
John R. Ma@, M.D.;fç
Roberta R. Miller,M.D., F.C.C.P;* W R. Eric jamieson, M.D.;II,
and Fritz Baumgartner,
M.D.t
Tuberculosis is increasing in prevalence in North America,
mainly due to HIV infection. We describe an unusual case
of TB
of the
thymus
in a HJ.V
sero-negative
Filipino
immigrant who preoperatively was thought to have a
thymoma. We describe the clinical, radiologic and patho
logic findings and review the literature on TB of the
thymus.
(Chest 1992; 1604-05)
fter a steady decline in the number of cases of tubercu
losis (TB) reported
in North American
over a number
ofyears, this trend was reversed in the mid-80s. This change
has been ascribed to the effects ofhuman immunodeficiency
virus (HIV) infection. ‘¿
Although HIV-associated TB has been
associated
with a greater
incidence
of extrapulmonary
dis
ease, a review of the literature failed to identify any recent
cases
of thymic
TB. In addition,
to our knowledge,
the CT
findings in thymic TB have not been described. In this
report,
we
describe
a culture-proven
thymus
which was imaged
case
of TB of the
with CT
CASE REPORT
A 20-yr-old Filipino woman presented in February 1991 with a
first-trimester miscarriage. She admitted to a four.month history of
cough and positional dyspnea, which had not responded to treatment
with oral antibiotics or albuterol (salbutamol).A routine chest
roentgenogram
on admission showed a large anterior mediastinal
mass (Fig 1). A contrast-enhanced
CT scan of the chest revealed a
6 x 4 x 7-cm cystic and solid mass lying immediately anterior to the
aortic arch in the anterior mediastinum
(Fig 2). There was flO
associated mediastinal adenopathy or pericardial effusion, and the
mass was separate from vascular structures. No abnormality was
seen in the lung parenchyma. Normal thymic tissue could not be
identified. There was no evidence of continuity with the thyroid,
which appeared normal. Due to the nonspecific findings, a differ
ential diagnosis was provided which included thymic lesions, germ
cell tumor, and lymphoma. For further clarification, a CT-guided
18-gauge needle aspirate was obtained, which showed lymphocytes,
histiocytes, and clumps of bland thymic epithelial cells. These
findings were interpreted as consistent with a thymoma. The patient
was then referred for an elective resection of the lesion at our
institution.
At the time of admission for resection, the patient had no new
FIGURE 1. Chest roentgenogram
on admission shows mediastinal
widening
at the level of the aortopulmonary
window. There are no
associated lung parenchymal
abnormalities.
Surgical resection was performed through a median sternotomy.
A large infiltrative anterior mediastinal mass was found, based in
the inferior part of the thymois. Thtal thymectomy with complete
resection ofgross disease was accomplished, but required resection
of a wedge of the left lung and mediastinal pleura. After surgery
the patient was found to have a left recurrent laryngeal nerve palsy.
Grossly; the thymic mass measured 11 x 7 cm. On section, there
was a 3.5-cm central cavity with shaggy walls and thick yellow
contents. In addition, multiple 1-cm to 2-cm nodules were found
throughout the gland, many of which were caseous. histologically,
there was extensivenecrotizinggranulomatousinflammation.Nec
rotizing granulomas were present in the left lung, which was
adherent to the thymus. Ziehl-Neelsen stains were positive for acid
fast bacilli (AFB), and thymus tissue cultures were subsequently
positive for Mycobacterium tuberculosis. Although there was an
element of reactive thymic epithelial proliferation in the areas of
inflammation, there wsu no evidence ofa thymoma.
Sputum
smears
after
surgery
were
negative
for AFB
but
grew
M tuberculosis organisms. A skin test with 5 TU of purified protein
derivative gave a 28-mm positive response. Serology for HIV
antibodies was negative, and both CD4 and CD8 helper cell counts
were normal. The patient was started on and oral therapy with
rifampin (600 mg), pyrazinamide (1.5 g), isoniazid (300 mg), and
complaints. In particular, there was no history ofnight sweats, fever,
weight loss, or risk factors for HIV infection. Her history revealed
that she had immigrated from the Philippines in 1987 and was
uncertain as to her previous exposure to TB . She had received BCG
asa child. The findings from clinical examinationwere unremark
able, and a repeat chest roentgenogram confirmed that the anterior
mediastinal mass was unchanged. The results of spirometry and
flow volume studies were normal.
@
*Fn)m the Departments of Respiratory Medicine, Radiology Pa
thology, and Cardiac Surgery, University of British Columbia,
Vancouver General hospital, Vancouver, Canada.
tDepartment
of Respiratory Medicine.
@Department of Radiology.
§Department of Pathology
Department of Cardiac Surger@:
Reprint requests: Dr. FitzGerald, 2775 Heather Street, Vancouver
General Hospital, Vancouver, BC, Canadi@i
V5Z 3J5
1604
FIGURE 2. Computed
outflow
tract,
tomographic
demonstrating
scan
a solid
at the level
and
cystic
ofthe
mass
pulmonary
lying
in the
anterior mediastinum . Lzav-density cystic areas (arrows) represent
necrotic areas within ttIl)erculosis of thymus.
iliberculosis of the Thymus (FitzGerald at a!)
Downloaded From: http://journal.publications.chestnet.org/pdfaccess.ashx?url=/data/journals/chest/21658/ on 06/16/2017
ethambutol (800 mg) daily. Once the patient's organism was found
to be fully sensitive, the ethambutol was discontinued. Following
discharge the patient is tolerating her medication welland improving
8 Trastek VF. Management of mediastinal tumors. Ann Thorac
Surg 1987; 44:227-28
9 Fradet G, Evans KG, Nelems B, Miller RE, MUller NL. Primary
anterior mediastinal tumours:an investigationalalgorithm. Can
J Surg 1989;32:139-42
symptomatically.
DISCUSSION
Although TB involvement of mediastinal nodes is corn
mon, TB of the thymus is extremely rare.' It has been
suggested that thymic tuberculosis represents remnants of
postprimary localized mediastinal lyrnphadenitis.' A review
of the English literature uncovered only three other cases of
thymic tuberculosis,@― of which only one was culture
positive.―
The management of anterior mediastinal masses varies
according to the presumptive diagnosis.@―
The most common
lesionsbo include
thyrnoma
and benign
germ cell tumors,
for
which primary surgical therapy is appropriate, and lym
phoma and malignant germ cell tumors, for which primary
nonsurgical therapy is appropriate. Although CT is useful in
assessing
the extent
of these masses,
all of these lesions
was
then
performed
to
establish
Ann Thorac Surg 1987;44:229-37
11 Suster 5, Rosaf J. Histology of the normal thymus. Am J Surg
Pathol 1990; 14:284-303
ChristmasCandyMaker'sAsthma*
IgG4-MedlatedPectinAllergy
Allen Kraut, M.D.; Zhikeng I@ng, M.D.; Allan B. Becker, M.D.;
and C. I1@ter
W Warren,M.D.
may
present as a cystic and solid mass. As this case demonstrates,
thyrnic TB with central necrosis can also have this appear
ance. An 18-gauge needle aspiration biopsy under CT
guidance
10 Davis RD Jr, Oldham HN Jr, Sabiston DC Jr. Primary cysts and
neoplasms of the mediastinum: recent changes in clinical
presentation,
methods of diagnosis, management,
and results.
a histologic
preoperative diagnosis; however, the role ofneedle aspiration
biopsy of anterior mediastinal masses is controversial.― The
reason for the controversy is illustrated in this case, where
there was an erroneous interpretation of thymoma due to
the presence of clumps of thymic epithelial cells and
We evaluated a 29-year-old candy maker with no history of
asthma who developed asthma after exposure to pectin, a
compound manufactured from fruits and fruit rinds. Fol
lowing eight years of employment during which he added
pectin to a recipe for Christmascandies,the candymaker
developed acute respiratory symptoms. Challenge testing
with the pectin mixture caused a 40 percent
decrease
in
FEV,. Skin prick testing was positive to the pectin extract.
Total IgE was normal and pectin-specific
IgE antibodies
lymphocytes in the aspirate. The source of these epithelial
were not detected. A stronglypositivepectin-specificIgC4
clusters
antibody response was present that was not detected in a
appears to be reactive
thymic epithelial
proliferation
at the edge of the granulomas. This type of reactive change
is well known to be a source of diagnostic confusion― and
led to surgical excision in this case.
control serum and could be inhibited by the addition of
pectin. Antigen-specific
IgC4 should be sought in IgE
In summary, we present a case of thymic tuberculosis
(Cheat 1992; 1605-07)
which simulated a low-grade thymic epithelial
negativecasesof occupationalasthma.
tumor both
radiologically and on aspiration needle biopsy. This case
demonstrates that thymic TB can appear as a cystic and
solid mass on contrast-enhanced
CT scan. In retrospect, the
ELISAenzyme-linked
immunosorbent
assay; PBS-T20
phosphate-buffered
saline with 0.05% 1\@veen20
correct diagnosis could only have been established nonsur
gically with a very high index of suspicion.
O
ccupational asthma has been reported following expo
sure to a variety of organic compounds.'4
1 FitzGerald JM, Grzybowski 5, Allen EA. The impact of human
immunodeficiency virus infection on tuberculosis and its control.
Chest 1991; 100:191-200
2 Peabody JW, Brown RB, Sullivan MB, Gannon A. Mediastinal
granulomas: a revised concept of their incidence and etiology.
J Thorac Surg 1958;35:384-96
3 Karlson KE, Timmes
JJ. Granulomata
Pectin, a
product manufactured from fruits and fruit rinds, is a large
REFERENCES
of the mediastinum
surgically treated and followed up to nine years. J Thorac Surg
1958; 35:617-27
4 Duprez A, Cordier R, Schmitz P Tuberculoma of the thymus:
first case of surgical excision. J Thorac Cardiovasc Surg 1962;
44:115-20
5 Silvola HJ, Lahdesmaki M. On tuberculosis of the thymus. Ann
Chir Gynaecol Fenn 1966; 55:27-30
6 Peabody JW, Walkup HE, Murphy JD. Tuberculoma of the
mediastinum: report of the first culturally proved case. J Thorac
Surg 1958; 35:397-99
7 Ferguson MK, Lee E, Skinner DB, Little AG. Selective
operative approach for diagnosis and treatment
of anterior
mediastinal masses. Ann Thorac Surg 1987; 44:583-86
molecular weight organic compound (150,000 to 500,000
Daltons) made up of a mixture of methyl-esterified
galactu
ronan, galactan, and araban.@ To our knowledge, there have
been
only
two
reports
of occupational
asthma
following
pectin exposure.―'
Cases of occupational
asthma due to high molecular
weight compounds are usually, but not always, mediated by
IgE antibodies.' In recent years, the role of IgG4 in the
etiology of a variety of allergic disorders
in general@―and
occupational allergic disorders in particular' has received
increasing scrutiny. Thus, IgG4 may play a role in some
cases of occupational
asthma
that are not mediated
by IgE.
We wish to report a case of occupational asthma with
increased pectin-specific
IgG4.
“¿From
the MFL-Occupational Health Center (Dr. Kraut),and the
FacultyofMedicine,
University ofManitoba,
Winnipeg,
Manitoba,
Canada (Drs. Kraut, Peng, Becker, and Warren).
Reprint requests: Dr. Kraut, NA@618,7% McDermot, WThnipeg,
MN, Canada Pt3E0W3
CHEST I 102 I 5 I NOVEMBER, 1992
Downloaded From: http://journal.publications.chestnet.org/pdfaccess.ashx?url=/data/journals/chest/21658/ on 06/16/2017
1605