DOI:10.2214/AJR.05.1285
AJR 2006; 187:W235
© American Roentgen Ray Society
Physiologic 18F-FDG Uptake in the Serratus Anterior Muscle: A Potential False-Positive on PET Resolved with PET/CT
Barton F. Branstetter, IV
University of Pittsburgh Medical Center Pittsburgh, PA
15213
Physiologic uptake of 18F-FDG can be easily confused with
abnormality on PET. PET/CT has better accuracy than PET, but physiologic
18F-FDG uptake on PET/CT may still be confusing when it is
asymmetric [1,
2].
A 52-year-old man with a history of oral cavity squamous cell carcinoma
presented for routine follow-up with combined PET/CT. His treatment regimen
had included primary tumor resection, bilateral neck dissections,
chemotherapy, and external beam radiation. On the PET images, a focal area of
increased 18F-FDG uptake was noted
(Fig. 5A). This focus was
initially interpreted as an axillary lymph node on the PET images alone, but
after fusion images were evaluated, the uptake was shown to be associated with
a muscle running from the upper tip of the scapular wing to the lateral aspect
of the first two ribs (Fig.
5B). The scan was then interpreted as negative for residual or
recurrent tumor. No causative motions, such as shoulder twitch, were noted in
the patient.
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Fig. 5B —52-year-old man with history of oral cavity squamous cell
carcinoma. Corresponding axial enhanced CT image shows muscle responsible for
physiologic uptake: second digitation of serratus anterior (arrow).
First digitation is marked with arrowhead.
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The serratus anterior muscle arises on the medial aspect of the scapula and
attaches to the first eight ribs by interdigitating with the intercostal
muscles. Its function is to keep the scapula close to the posterior chest wall
(i.e., to prevent scapular winging). The first two digitations of the serratus
anterior arise from the superomedial tip of the scapula and are anatomically
distinct from the remainder of the muscle
[3]. These two muscular slips
insert on the lateral aspect of the first and second ribs.
Physiologic muscular uptake of 18F-FDG is a frequent finding on
PET and PET/CT. A thorough knowledge of muscular anatomy is necessary to avoid
confusing physiologic uptake with abnormality.
References
- Branstetter BF IV, Blodgett TM, Zimmer LA, et al. Head and neck
malignancy: is PET/CT more accurate than PET or CT alone?
Radiology 2005;235
: 580-586[Abstract/Free Full Text]
- Blodgett TM, Fukui MB, Snyderman CH, et al. Combined PET-CT in the
head and neck. 1 Physiologic, altered physiologic, and artifactual FDG uptake.
RadioGraphics 2005;25
: 897-912[Abstract/Free Full Text]
- Gray H. Anatomy, descriptive and surgical.
Philadelphia: Courage Books, 1901:381
-382
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