Anatomic Pathology / DIAGNOSTIC YIELD AND SIMULTANEOUS BIOPSIES
Diagnostic Yield Associated With Multiple Simultaneous
Skeletal Muscle Biopsies
Richard A. Prayson, MD
Key Words: Muscle biopsy; Skeletal muscle biopsy; Inflammatory myopathy; Vasculitis
DOI: 10.1309/78B3M0TGJYT4RUUM
Abstract
Certain skeletal muscle disorders, such as
inflammatory myopathies, may show regional
variability, prompting consideration of simultaneous
biopsy of more than 1 muscle to increase the likelihood
of diagnosis. There are few data in the literature to
support this approach. This study is a retrospective 8year review of 99 cases (52 men; mean age, 61.8 years)
who had multiple muscles biopsied simultaneously. The
most common clinical symptoms prompting biopsy
included weakness in 83 cases and myalgia in 15. The
most common diagnoses were as follows: neurogenic
atrophy, 48; inflammatory myopathy, excluding
inclusion body myositis, 29; and type II muscle fiber
atrophy, 24. Diagnoses were the same in both biopsied
muscles in 54 cases (55%). In 17 cases, a diagnosis was
made from only 1 biopsy. Of 29 inflammatory
myopathies and vasculitis (excluding inclusion body
myositis), a diagnosis could be made from only 1 of the
2 biopsies in 10 cases (34%). In a significant subset of
cases, a potentially treatable inflammatory myopathic
condition might have been missed if only 1 site had
been biopsied, justifying biopsy of 2 sites in suspected
cases of inflammatory myopathy.
The role of muscle biopsy in diagnosis or corroborating a
clinical impression in a variety of disease processes is well
established.1-7 Although certain muscle groups are typically the
target of a nondirected biopsy in a patient with a more diffuse
disease process, the biopsy is generally directed at a muscle
that is likely to yield diagnostic information. In selecting a
muscle for biopsy, care should be taken not to biopsy a muscle
that is likely to demonstrate nonspecific end-stage changes.
Certain pathologic processes, such as myositis and vasculitis, may be diffuse or localized. One strategy for increasing diagnostic yield is to biopsy 2 different potentially
involved muscle groups at the same time, hoping that at least
one, if not both biopsied sites, will yield diagnostic information. In contrast with many types of neuromuscular disease for
which there is no definitive treatment, many inflammatory
myopathic and vasculitic conditions respond to pharmacologic treatment. There is a paucity of literature, however, that
specifically addresses the issue of increased diagnostic yield
in the setting of multiple simultaneous biopsies.
The purpose of this study was to retrospectively review 1
institution’s experience with patients who had 2 or more muscles biopsied simultaneously for the evaluation of neuromuscular disease. Particular attention is given to the subset of patients
in whom a potentially treatable inflammatory myopathic or vasculitic condition was diagnosable from only 1 of the biopsies.
Materials and Methods
Institutional review board approval was obtained before
commencement of this study. The surgical pathology computer system was searched for cases during an 8-year period
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(January 1996 to January 2004) in which 2 or more skeletal muscle biopsy specimens obtained at the same time
were evaluated for neuromuscular disease. There were 99
cases that fulfilled these criteria and formed the study
group. In each case, histologic sections, pathology reports,
and medical records were reviewed, when available, to
obtain information about clinical manifestations, sites
biopsied, and diagnoses made. Particular attention was
given to comparing diagnoses made between biopsied sites
in the same patient.
Routine histologic evaluation of muscle biopsy specimens included sections stained with H&E, acid phosphatase,
alkaline phosphatase, nonspecific esterase, nicotinamide adenine dinucleotide reduced (NADH), cytochrome oxidase,
adenosine triphosphatase at pH 4.6 and pH 9.8, periodic
acid–Schiff, oil red O, and sulfonated alcian blue.
Diagnoses were compared between different biopsied
muscles. Information regarding age, sex, symptoms or manifestations prompting biopsy, and muscle biopsied were
obtained through review of the medical records, including
pathology reports.
Results
The study group included 99 cases. Patients ranged in age
from 23 to 92 years (mean, 61.8 years). There were 52 men
and 47 women. Two different muscles were biopsied simultaneously in 97 patients. The remaining 2 patients had 3 different muscles biopsied simultaneously.
The most common clinical symptoms or manifestations
prompting biopsy included weakness in 83 cases, myalgia in
15, and elevated enzyme levels (most commonly creatinine
kinase) in 8. Less common clinical manifestations included
the following: rash, 3; generalized lethargy or fatigue, 2; dysphagia, 2; shortness of breath, 1; and weight loss, 1. In 4 cases,
information regarding clinical symptomatology was not available. Thirty patients underwent biopsy because of questions
about possible inflammatory myopathy.
The most commonly biopsied muscles included the deltoid in 70, vastus lateralis in 44, and quadriceps in 27. The less
commonly biopsied sites included the following: biceps, 10;
triceps, 9; thigh region, not otherwise specified, 8; rectus
femoris, 7; gastrocnemius, 4; upper arm region, not otherwise
specified, 4; gluteus maximus, 2; paraspinal muscles, 2; trapezoid, 1; pectoralis, 1; sternocleidomastoid, 1; temporalis, 1;
brachialis, 1; infraspinatus, 2; anterior tibialis, 1; peroneus, 1;
and calf region, not otherwise specified, 1. In 85 cases, the
muscles biopsied were all on the same side. In 8 cases, the
biopsies were taken from muscles on opposite sides of the
body. In the remaining 6 cases, the laterality of the biopsied
muscles was not known.
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The most common diagnoses made included denervation
or neurogenic atrophy in 48 cases, type II muscle fiber atrophy
in 24, and an inflammatory myopathic condition consistent
with polymyositis in 23. An additional 8 cases were diagnosed
as inclusion body myositis ❚Image 1❚, 3 as dermatomyositis
❚Image 2❚, and 1 as a granulomatous inflammatory myopathic
condition. One case demonstrated marked acute inflammatory
changes consistent with an acute bacterial myositis. One additional case was diagnosed as necrotizing vasculitis consistent
with polyarteritis nodosa. In 20 cases, biopsy specimens
demonstrated cytochrome oxidase–negative muscle fibers
(excluding cases of inclusion body myositis). Additional
encountered pathologic diagnoses included type I muscle fiber
atrophy in 1 case, nonspecific mild inflammatory changes in 5,
increased lipid deposition in 2, rhabdomyolysis in 2, and acute
myositis in 1. In 5 cases, no pathologic abnormality was
revealed by either of the biopsies. In 25 biopsied muscles (deltoid, 10; vastus lateralis, 6; quadriceps, 4; triceps, 2; and other,
3), no pathologic abnormalities were identified.
Electron microscopic evaluation of 1 of the biopsied muscles was performed in 37 cases. In only 2 cases were both
muscles examined ultrastructurally. In 10 cases, additional
diagnoses were made based on ultrastructural evaluation of
the muscle, including mitochondrial abnormalities in 4 cases
and increased glycogen deposition in 6 cases. In 10 cases, the
electron microscopic findings confirmed the light microscopic impression of inclusion body myositis or a mitochondrial
abnormality (as suggested by cytochrome oxidase staining
abnormalities).
In 54 cases, the diagnoses were the same in the biopsied
muscles. In the remaining 45 cases, a different diagnosis was
made from each biopsy. In 17 of these 45 cases, a diagnosis
was made from only 1 of the biopsied muscles; the other
revealed no significant pathologic change ❚Image 3❚. The
details of these 17 cases are outlined in ❚Table 1❚. These
patients included 9 women and 8 men who ranged in age from
33 to 79 years (mean, 57.2 years). Diagnoses made in this
group included the following: denervation atrophy, 6;
polymyositis, 4; type II atrophy, 3; nonspecific myopathic
changes, 2; mitochondrial abnormality, 1; and inclusion body
myositis, 1.
Of particular significance were the 29 potentially treatable inflammatory myopathic or vasculitic (excluding inclusion body myositis) cases ❚Table 2❚. The patients in this group
included 18 women and 11 men who ranged in age from 23 to
87 years (mean, 61.6 years). In 10 cases (1, 3, 10, 12, 16, 18,
20, 23, 24, and 27), a definitive diagnosis of potentially treatable inflammatory myopathy or vasculitic condition could be
made from only 1 of the 2 biopsies (34%). In 8 of the 10 cases,
a diagnosis of polymyositis was given. One patient had a granulomatous inflammatory condition, and 1 had a necrotizing
vasculitis consistent with polyarteritis nodosa.
© American Society for Clinical Pathology
Anatomic Pathology / ORIGINAL ARTICLE
A
B
C
D
❚Image 1❚ A, Deltoid muscle in a 68-year-old man showing a nonspecific, mild variation in muscle fiber size (H&E, original
magnification ×400). B and C, Vastus lateralis muscle marked by myopathic changes consistent with inclusion body myositis,
including muscle degeneration, regeneration, and rimmed vacuoles (H&E, original magnification ×400). D, Ultrastructural evidence
of tubulofilaments in the vastus lateralis biopsy confirms the diagnosis of inclusion body myositis (original magnification ×13,000).
Discussion
The diagnostic usefulness of a muscle biopsy in the evaluation of a wide spectrum of neuromuscular disorders is well
established. Experience has suggested that certain disorders,
such as polymyositis and vasculitis, may be localized, and
careful selection of a muscle to biopsy in these situations is
important. An optimal muscle for biopsy includes one that
will hopefully demonstrate diagnostic pathologic features and
not nonspecific end-stage changes. It is well recognized that
muscles that have been recently traumatized do not serve as
good targets for biopsy because they frequently show changes
that may resemble an inflammatory myopathy.
With certain other muscle diseases, the extent of findings
is less well established (ie, it is not clearly known whether the
pathologic process is widespread or focally present). In this
latter scenario, it again makes sense to target a muscle that is
clinically involved for purposes of biopsy. In certain conditions such as the inflammatory myopathies and vasculitis,
given the potential focality of the lesion, it makes empiric
sense to biopsy more than 1 site with the hope of increasing
the diagnostic yield.
There is relatively little information in the literature substantiating such practice. Up to 25% of patients who have clinical features of polymyositis have no evidence of inflammation in their muscle biopsy specimens.8,9 The significance of
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A
B
❚Image 2❚ A, Right vastus lateralis muscle in a 32-year-old woman showing vascular-based chronic inflammation suggestive of an
inflammatory myopathic or vasculitis process (H&E, original magnification ×200). B, Right deltoid muscle from the same patient
showing evidence of perifascicular atrophy highly suggestive of dermatomyositis (H&E, original magnification ×100).
A
B
❚Image 3❚ A, Vastus lateralis muscle biopsy specimen from a 42-year-old woman with inflammatory myopathic changes (chronic
endomysial inflammation, muscle fiber degeneration, and muscle fiber regeneration) consistent with polymyositis (H&E, original
magnification ×400). B, Biceps muscle in the same patient showing no evidence of inflammatory myopathic changes (H&E,
original magnification ×200).
this lies in the fact that many of the inflammatory myopathic
conditions are potentially treatable with steroids and immunosuppressive agents. Because therapeutic agents are not without
side effects, confirmation of a clinical diagnosis is useful. A
corollary to this is the fact that certain inflammatory
myopathies, most notably inclusion body myositis, are not particularly responsive to such treatment. The pathology of inclusion body myositis overlaps somewhat with polymyositis, and,
therefore, biopsy confirmation of the diagnosis is again helpful
in avoiding unnecessary therapeutic complications.
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Even within the same muscle, there may be variability in
the presence of inflammatory myopathic changes in patients
with myositis. Use of a percutaneous needle biopsy technique
to obtain muscle tissue has been reported in several studies to be
advantageous in that it allows for the procurement of “diagnostic tissue” under local anesthesia, causing less scarring, and it is
associated with significantly less pain and bleeding than more
traditional open biopsy procedures.10-13 Haddad et al8 described
a small series of patients diagnosed with polymyositis using a
percutaneous needle biopsy procedure. Even in multiple needle
© American Society for Clinical Pathology
Anatomic Pathology / ORIGINAL ARTICLE
❚Table 1❚
Summary of Patients Who Had One Normal Biopsy Result
Case No./
Sex/Age (y)
1/F/58
2/M/70
3/F/55
4/F/57
5/F/79
6/F/55
7/F/54
8/M/72
9/M/38
10/F/33
11/M/37
12/F/69
13/M/77
14/M/57
15/F/51
16/M/74
17/M/37
Muscle 1
Diagnosis, Muscle 1
Muscle 2
Diagnosis, Muscle 2
L vastus lateralis
L deltoid
L deltoid
L biceps
Vastus lateralis
L deltoid
R deltoid
L thigh
R deltoid
L deltoid
L vastus lateralis
L deltoid
L arm
L quadriceps
L deltoid
L vastus lateralis
R brachialis
Denervation atrophy
Nonspecific myopathic changes
NPC
Type II atrophy
Polymyositis
Polymyositis
Type II atrophy
NPC
NPC
NPC
NPC
NPC
NPC
Denervation atrophy
NPC
NPC
NPC
L deltoid
L vastus lateralis
L quadriceps
L vastus lateralis
Deltoid
L quadriceps
R rectus femoris
R thigh
R vastus lateralis
L paraspinal
L deltoid
L vastus lateralis
L vastus lateralis
L deltoid
L quadriceps
L deltoid
R triceps
NPC
NPC
Type II atrophy
NPC
NPC
NPC
NPC
Denervation atrophy
Denervation atrophy
Chronic active neurogenic atrophy
Mitochondrial abnormality
Nonspecific myopathic changes
Inclusion body myositis
NPC
Polymyositis
Polymyositis
Neurogenic atrophy
L, left; NPC, no pathologic changes; R, right.
❚Table 2❚
Summary of Patients With Potentially Treatable Inflammatory Myopathy or Vasculitis Found by Biopsy
Case No./
Sex/Age (y)
Muscle 1
1/M/64
L vastus lateralis
2/F/47
3/M/73
4/F/75
L thigh
R vastus lateralis
L deltoid
5/F/26
6/F/69
7/F/23
8/M/71
R upper arm
R vastus lateralis
R lateral thigh
R vastus lateralis
9/F/71
L biceps
10/F/79
11/F/55
12/F/83
13/M/52
14/F/86
15/M/57
Vastus lateralis
L deltoid
R forearm
Pectoralis
R temporalis
R rectus femoris
16/F/57
17/F/87
R deltoid
L deltoid
18/F/69
19/M/55
20/F/51
21/F/62
22/M/65
23/M/74
24/M/72
Paraspinal
R deltoid
L deltoid
R deltoid
L biceps
L vastus lateralis
R deltoid
25/M/44
26/F/44
R vastus lateralis
L deltoid
27/F/87
28/F/28
29/M/61
R deltoid
L vastus lateralis
L quadriceps
Diagnosis, Muscle 1
Inflammatory myopathy
with granulomas
Dermatomyositis
Type II atrophy
Polymyositis; denervation
atrophy
Polymyositis
Polymyositis
Polymyositis
Polymyositis; denervation atrophy;
mitochondrial abnormality
Polymyositis; type II atrophy;
mitochondrial abnormality
Polymyositis
Polymyositis
Polymyositis
Acute bacterial myositis
Polymyositis
Polymyositis; type II atrophy;
mitochondrial abnormality
Nonspecific chronic inflammation
Polymyositis; mitochondrial
abnormality
Polymyositis
Polymyositis, denervation atrophy
Nonspecific chronic inflammation
Dermatomyositis
Polymyositis
Denervation atrophy
Polymyositis; denervation atrophy
Polymyositis; denervation atrophy
Dermatomyositis; denervation
atrophy
Nonspecific chronic inflammation
Polymyositis; type IIb atrophy
Targetoid fibers
Muscle 2
L triceps
L deltoid
R deltoid
L vastus lateralis
R thigh
R deltoid
R medial thigh
R deltoid
L vastus lateralis
Deltoid
L quadriceps
R thigh
Sternocleidomastoid
R deltoid
L deltoid
R quadriceps
L vastus lateralis
Deltoid
R vastus lateralis
L quadriceps
R vastus lateralis
L vastus lateralis
L deltoid
R infraspinatus
Diagnosis, Muscle 2
Denervation atrophy; mild inflammation;
mitochondrial abnormality
Dermatomyositis; denervation atrophy
Polymyositis; mitochondrial abnormality
Polymyositis; type II atrophy; denervation
atrophy
Polymyositis
Polymyositis; type II atrophy
Polymyositis
Polymyositis; mitochondrial abnormality
Polymyositis; type II atrophy; mitochondrial
abnormality
Type II atrophy
Polymyositis
Denervation atrophy
Acute bacterial myositis
Polymyositis
Polymyositis; type II atrophy; mitochondrial
abnormality
Necrotizing vasculitis
Polymyositis; mitochondrial abnormality
R deltoid
L vastus lateralis
Regenerating fibers
Polymyositis; denervation atrophy
Polymyositis
Dermatomyositis
Polymyositis
Polymyositis
Denervation atrophy; degenerating and
regenerating fibers
Regenerating fibers; polymyositis
Dermatomyositis; denervation atrophy
R vastus lateralis
L deltoid
L deltoid
Polymyositis
Polymyositis
Polymyositis; mitochondrial abnormality
L, left; R, right.
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cores obtained from the same muscle, inflammatory changes
were not observed in all of the core specimens. They recommended that if one was going to use a needle biopsy approach
to muscle biopsy, a potentially higher yield may result from
obtaining multiple biopsy cores.
In the present study, the most common pathology identified was that of denervation atrophy. The pathology of denervation atrophy is somewhat nonspecific and is the result of
secondary changes in muscle resulting from primary pathology affecting the peripheral nervous system or spinal cord. This
condition is treatable only to the extent that the more proximal
cause of the denervation atrophy is treatable. In slightly fewer
than half of the patients who had 2 muscle biopsies, different
diagnoses were made from each biopsy. Of particular significance was the fact that in 29 cases of inflammatory myopathy
and vasculitis, the condition was diagnosed from only 1 biopsy in 10 cases. These results would suggest that the diagnostic
yield for biopsy of 2 muscles justifies such an approach.
Although the therapeutic ramifications are perhaps not as
dramatic in other conditions, there were other cases in which
the diagnosis obtained from only 1 biopsy might affect clinical management. For example, mitochondrial myopathy,
although not directly curable, if diagnosed, may offer some
guidance in terms of clinical management of the patient and
suggestion for potential supportive approaches.
Although the number of the cases of vasculitis was relatively small in this series, 2 patients were given diagnoses of
polyarteritis nodosa based on the presence of necrotizing vasculitis in 1 of the biopsied muscles. Similar to the inflammatory myopathies, vasculitis is classically a focalized process and
may affect the skeletal muscle in up to 20% of patients.14 A
similar issue of biopsy of multiple sites (usually a muscle and
peripheral nerve) has also been raised in the setting of evaluating vasculitis. In 1 series of 40 patients evaluated with skeletal
muscle vasculitis arising outside the setting of inflammatory
myopathy, 33 patients had a concomitant sural nerve biopsy
and vasculitis was also identified in the peripheral nerve in 26
(79%) of the 33 patients.15 Another series of 202 biopsies noted
that concomitant muscle biopsy improved the diagnostic yield
by 27%.16 The implication is that in approximately 20% of
cases, the vasculitis would not have been diagnosed had a muscle biopsy not been performed. Again, this adds some credence
to the notion that biopsy of multiple sites also increases one’s
diagnostic yield for making a diagnosis of vasculitis.
The empiric practice of performing 2 simultaneous biopsies to increase diagnostic yield seems to be justified. In 17
cases in the current series (17%), pathology was observed in
only 1 of 2 biopsied muscles; the other biopsied muscle showed
no significant pathologic changes. Of perhaps more clinical significance, a third of potentially treatable inflammatory myopathic conditions and vasculitis cases were diagnosable in only
1 of the 2 biopsied muscles.
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From the Department of Anatomic Pathology, Cleveland Clinic
Foundation, Cleveland, OH.
Address correspondence to Dr Prayson: Dept of Anatomic
Pathology (L25), Cleveland Clinic Foundation, 9500 Euclid Ave,
Cleveland OH 44195.
Acknowledgment: Special thanks to Denise Egleton for
assistance in the preparation of this manuscript.
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