Gynecomastia Medical Column: One-Sided Male Breast Enlargement- Conditions to Differentiate
Can one-sided breast enlargement in men be gynecomastia, or could it be another condition?
Yes. While unilateral gynecomastia is not uncommon,
one-sided breast enlargement can also be caused by benign tumors, male breast cancer, or a breast abscess.
A breast ultrasound is essential for an accurate diagnosis.
Hello, I am Jihoon Moon from Lesarts Plastic Surgery.
In last week’s Gynecomastia Medical Column,
we discussed the mechanisms behind
the breast pain commonly experienced
by patients with gynecomastia
and explained how it can be
a natural sign of glandular tissue growth.
In this article,
I would like to answer
one of the most common questions
about gynecomastia,
regardless of whether breast pain is present.
“My chest isn’t symmetrical.
One side sticks out much more than the other.
Could this still be gynecomastia?”“I’m worried it could be something more serious.”
The short answer is yes.
Although gynecomastia
most commonly affects
both breasts simultaneously,
unilateral gynecomastia,
which affects only one side,
accounts for approximately 10–15% of cases.
However,
when only one breast
appears noticeably enlarged,
there are several important
medical conditions
that should be differentiated
from gynecomastia.
In today’s Gynecomastia Medical Column,
we will take a closer look
at the various causes
of unilateral breast enlargement
and explain why
an accurate diagnosis
is so important.
1. Natural Body Asymmetry: Normal Variation
The human body
is not perfectly symmetrical.
Just as the dominant arm
often has greater muscle mass,
the chest can also show
natural differences
in size and shape.
In clinical practice,
many patients
who visit the clinic
because of breast asymmetry
are ultimately diagnosed
with normal variation,
showing no evidence
of abnormal glandular tissue growth.
Male Gynecomastia Diagnosis – Could Uneven Breasts Be Gynecomastia?
✔ Anatomical Characteristics
Interestingly,
both clinical experience
and published studies suggest
that the left breast
is often slightly larger
than the right.
This difference may be related
to the position of the heart,
subtle asymmetry
of the chest wall,
differences in pectoral muscle development
between the dominant and non-dominant side,
or variations
in subcutaneous fat thickness.
✔ Key Points for Differentiation
If you do not feel
a firm glandular tissue mass
beneath the areola,
and the asymmetry
is caused only
by differences in muscle shape
or fat thickness,
it is generally considered
a normal anatomical variation
and is usually
not a cause for concern.
2. Unilateral Gynecomastia – When Only One Breast Responds to Hormonal Changes
When hormonal imbalance
between androgens
and estrogens occurs,
the glandular tissue
may begin to enlarge.
In some patients,
both breasts
do not respond equally
to hormonal stimulation.
Instead,
only one side
becomes more sensitive
to these hormonal changes,
leading to abnormal enlargement.
This condition
is known as
Unilateral Gynecomastia.
Unilateral Gynecomastia – Dr. Jihoon Moon, Lesarts Plastic Surgery
✔ Key Clinical Feature: Changes in the Areola
One of the most important features
that distinguishes unilateral gynecomastia
from normal breast asymmetry
or other conditions
is a change in the areola.
As the glandular tissue enlarges,
it pushes the overlying skin outward,
causing the affected areola
to appear noticeably larger
than the opposite side.
✔ Physical Examination Findings
When gently pressing
beneath the areola,
a relatively well-defined,
firm glandular tissue mass
can often be felt,
unlike the normal side.
This condition
commonly develops
during adolescence
because of hormonal changes,
or in adulthood
after taking certain medications,
such as hair-loss medication,
stomach medication,
or anabolic steroids.
Although only one side
may enlarge initially,
the opposite breast
often develops glandular tissue
later as well,
resulting in bilateral gynecomastia.
3. Benign Breast Tumors – A Common Cause of Unilateral Breast Enlargement
Many people assume
that benign breast tumors
occur only in women,
but this is a misconception.
Because men also have
glandular breast tissue,
various benign breast tumors
can develop
and cause noticeable
unilateral breast enlargement.
Fibroadenoma, Intraductal Papilloma, Lipoma, and Epidermoid Cyst in Men – Lesarts Plastic Surgery
✔ Fibroadenoma and Intraductal Papilloma
Although fibroadenoma
is most commonly associated
with female breast disease,
it can rarely develop
in male glandular breast tissue.
On examination,
it is usually felt
as a firm, well-defined lump
that moves freely
beneath the skin.
An intraductal papilloma,
which develops
inside a milk duct,
may occasionally cause
bloody or clear nipple discharge.
✔ Lipoma and Epidermoid Cyst
Unlike gynecomastia,
these common benign tumors
develop within
the subcutaneous fat layer
or the skin appendages,
rather than the glandular tissue itself.
A lipoma
typically feels soft
and movable,
and in some cases
can grow quite large.
An epidermoid cyst
often has
a small central opening,
through which
foul-smelling keratin material
may be expressed,
making it relatively easy
to distinguish
from gynecomastia
during physical examination.
4. Male Breast Cancer – A Condition That Must Be Carefully Distinguished
Among all causes
of unilateral breast enlargement,
male breast cancer
is the condition
that requires
the greatest attention.
Although men account
for less than 1%
of all breast cancer cases,
the disease
is often diagnosed
at a more advanced stage,
making early evaluation essential.
Unlike gynecomastia,
male breast cancer
develops almost exclusively
on one side of the chest.
Male Breast Cancer vs. Gynecomastia – Dr. Jihoon Moon, Lesarts Plastic Surgery
✔ Key Differences from Gynecomastia
① Fixed and Hard Mass
A gynecomastia lump
is usually elastic
and slightly movable
when examined.
In contrast,
a malignant breast tumor
feels extremely hard,
is firmly attached
to the surrounding tissues,
and does not move.
② Changes in the Nipple and Skin
As cancer grows,
it may pull
on the surrounding tissue,
causing nipple retraction
or skin thickening
with an orange-peel appearance.
③ Absence of Pain and Unilateral Growth
Early male breast cancer
is usually painless.
Unlike gynecomastia,
which often causes tenderness
during the early stage
of glandular tissue growth,
breast cancer typically presents
as a painless, hard lump
on only one side.
④ Enlarged Axillary Lymph Nodes
If a firm lump
is also felt
in the armpit,
representing enlarged
axillary lymph nodes,
prompt medical evaluation
is strongly recommended.
5. Breast Abscess – A Breast Infection with Acute Pain and Redness
If one breast
becomes rapidly enlarged
over several days
and is accompanied
by severe pain,
redness, and swelling,
a breast abscess
should be considered
rather than a tumor.
In some patients with gynecomastia, chronic non-infectious mastitis may also occur.
In these cases, mild tenderness may be present, but significant redness, swelling, or systemic symptoms are usually absent.
Male Breast Infection Treatment – Dr. Jihoon Moon, Lesarts Plastic Surgery
✔ Clinical Symptoms
A breast infection
usually develops
when bacteria enter
through a small nipple injury
or the milk ducts.
The affected breast
may become red, swollen,
and extremely tender,
with severe pain
even from light touch.
If the infection progresses
and pus accumulates,
it forms a breast abscess.
On examination,
the abscess may produce
a soft, fluctuant sensation,
and patients may also experience
fever or chills.
✔ Urgency of Treatment
Unlike gynecomastia,
a breast abscess
is not a cosmetic condition.
It is an urgent surgical infection
that requires
prompt antibiotic treatment,
and in some cases,
incision and drainage
to remove the accumulated pus.
6. Conclusion – Never Diagnose Unilateral Breast Enlargement by Appearance Alone
Having enlargement
of both breasts
can already be distressing.
When only one side
appears noticeably larger,
the anxiety and fear
patients experience
are often even greater.
However,
trying to diagnose yourself
by looking in the mirror—
thinking,
“My areola is larger, so this must be
unilateral gynecomastia,”
or,
“It doesn’t hurt, so maybe it’s cancer,”
can be medically dangerous.
Diagnosis of Male Breast Conditions – Dr. Jihoon Moon, Lesarts Plastic Surgery
Normal anatomical variation,
unilateral gynecomastia,
and both benign
and malignant breast tumors
cannot be distinguished
by appearance alone.
At our clinic,
the evaluation begins
with a thorough
physical examination
performed by the surgeon.
This is followed
by breast ultrasonography,
which provides
a detailed assessment
of the underlying tissue.
Within just a few minutes,
ultrasound can determine
whether the enlargement
is caused by glandular tissue growth
associated with gynecomastia,
a breast tumor,
or a breast abscess requiring treatment.
FAQ
Q1. Can gynecomastia affect only one breast?
Yes. Although gynecomastia usually develops on both sides, unilateral gynecomastia accounts for
approximately 10–15% of cases and may initially affect only one breast.
Q2. How can unilateral gynecomastia be distinguished from normal breast asymmetry?
Normal asymmetry is usually caused by differences in muscle or fat distribution without a firm glandular lump.
Unilateral gynecomastia typically presents with enlarged glandular tissue beneath the areola.
Q3. What other conditions can cause one-sided breast enlargement in men?
Besides gynecomastia, benign breast tumors, male breast cancer, lipomas, epidermoid cysts,
and breast abscesses can all cause unilateral breast enlargement.
Q4. What are the warning signs of male breast cancer?
A hard, fixed lump, nipple retraction, skin thickening, enlarged underarm lymph nodes,
and painless unilateral enlargement should all be evaluated promptly.
Q5. How is unilateral breast enlargement diagnosed?
A surgeon performs a physical examination followed by breast ultrasonography,
which can quickly determine whether the enlargement is caused by gynecomastia, a tumor, or an infection.
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