Summary: A 74-year-old man who underwent surgery for rectal cancer 2 years earlier
received a follow-up FDG-PET/CT examination. The study was performed with a Discovery
LS PET/CT camera (General Electric Medical Systems, Milwaukee, WI). Images were
obtained 50 min after intravenous injection of 185 MBq of FDG and performance of
CT-based attenuation correction. The acquisition and reconstruction parameters of the
FDG-PET scan were 2 min emission/bed, 7 bed position, and iterative reconstruction
(subset 14, number of iteration 2). The scanning parameters of the CT were Auto mA
(upper limit: 40 mA, noise index 20), 140kV, 5-mm section thickness, 15-mm table feed,
and a pitch of 4. The reconstructed images were converted to standardized uptake value
(SUV) images with patient’s body weight and injected dose of FDG. The patient had
a history of diabetes mellitus and liver cirrhosis with ascites; he had been taking a
potassium-holding diuretic, spironolactone, for 8 months. The patient also revealed
that he had been experiencing pain and swelling of the bilateral breast for a few
months immediately preceding the examination.
Proliferated bilateral mammary tissue was demonstrated on CT (Figure 1, upper
left), while increased FDG uptake in the bilateral anterior chest was observed on FDG-PET (SUVmax = 2.3, Figure 1, upper right), and the anatomical localization of FDG uptake in the mammary tissue was confirmed by co-registration of the FDG-PET and CT images (Figure 1, lower left).
Reports of physiological uptake of FDG in many organs have been increasing with
the growing frequency of FDG-PET examinations. In mammary tissue, physiological uptake,
uptake in benign tumors, and mastopathy have been also reported.1
Gynecomastia is a common clinical condition consisting of a benign proliferation of
male breast glandular tissue;2 its representative symptom is pain and
swelling of the breast. Gynecomastia itself is not a disease but, rather, a symptom of
an underlying imbalance in hormonal physiology—specifically, an increase in
estrogen action relative to androgen action at the breast tissue level.3,4
Transient gynecomastia occurs in the neonatal, pubertal, and senescent periods, and
some drugs and disease states are also known causes of gynecomastia.3-5
Spironolactone is a potassium-holding diuretic used to treat ascites due to liver
cirrhosis, and gynecomastia is a well-known side effect of the medication. Rose, et
al., reported that 6 of 16 patients treated with spironolactone developed
gynecomastia.6 According to this report,blood testosterone levels were
lower and estradiol levels higher in the gynecomastia group than they were in the
control group, indicating the disturbance in hormone balance with estrogen
predominating. The treatment for drug-induced gynecomastia is withdrawal of the
causative drug, leading to the disappearance of the symptom. In this case, the patient
suffered from liver cirrhosis with ascites, for which spironolactone had been
prescribed. Although liver cirrhosis also causes gynecomastia, due to the increase of
aromatization, the patient was taken off spironolactone after the FDG-PET/CT
examination, and his symptoms disappeared. Therefore, we considered this a case of
spironolactone-induced gynecomastia. FDG uptake in spironolactone-induced gynecomastia
is also reported by Fukuchi, et al.7
Gynecomastia is observed as a proliferation of breast tissue on CT and as dense
breast tissue on mammography. The relationship between breast density and FDG uptake
was reported by Vranjesevic, et al.8 FDG uptake in dense breast tissue was
significantly higher than that in fatty breast tissue. Uno, et al., compared FDG uptake
and ultrasonographic findings in fibrocystic mastopathy patients,1 FDG
uptake in mammary tissue correlated with severity of mastopathy. These reports suggest
that proliferation of breast tissue causes the increase of FDG uptake. FDG-PET/CT can
provide morphological and functional information simultaneously and assess the status
of mammary tissue through co-registration of both images.
We reported a case of spironolactone-induced gynecomastia revealed by FDG-PET/CT.
In male patients, history of medication and illness should be taken into account when
FDG uptake in bilateral mammary tissue is observed.
- Uno K, Yoshikawa K, Imazaki K, et al. FDG-PET evaluation of fibrocystic
mastopathy in patient with breast tumor. Eur J Nucl Med. 1994;21:S197.
- Nuttall FQ. Gynecomastia as a physical finding in normal men. J Clin Endocrinol
- Glass AR. Gynaecomastia. Endocrinol Metab Clin North Am. 1994;23:825-837.
- Braunstein GD. Gynecomastia. N Engl J Med. 1993;328:490-495.
- Mathur R, Braunstein GD. Gynecomastia: Pathomechanisms and treatment strategies.
Horm Res. 1997;48:95-102.
- Rose LI, Underwood RH, Newmark SR, et al. Pathophysiology of spironolactone-induced
gynecomastia. Ann Int Med. 1977;87:398-403.
- Fukuchi K, Sasaki H, Yokoya T, et al. Ga-67 citrate and F-18 FDG uptake in
spironolactone-induced gynecomastia. Clin Nucl Med. 2005;30:105-106.
- Vranjesevic D, Schiepers C, Silverman DH, et al. Relationship between 18F-FDG uptake
and breast density in women with normal breast tissue. J Nucl Med.