Expanded question: In a healthy 40-year-old male with unilateral left gynecomastia, does performing diagnostic tests such as mammography, ultrasound, or biopsy improve the assessment of breast cancer risk compared to clinical observation alone?

Answered on February 5, 2025
In the evaluation of unilateral gynecomastia in a healthy 40-year-old male, the use of diagnostic tests such as mammography, ultrasound, or biopsy should be considered based on the clinical context and findings. The medical literature suggests that routine imaging for gynecomastia is generally not warranted unless there are suspicious abnormalities on physical examination.
The study by Lapid et al. highlights that malignancies in the male breast are rare, and the probability of finding cancer when performing imaging of clinically benign findings is negligible. Therefore, routine imaging of gynecomastia should be discouraged unless there are suspicious abnormalities.[1] Similarly, the American College of Radiology (ACR) Appropriateness Criteria recommend mammography or digital breast tomosynthesis (DBT) as the initial imaging modality for men with an equivocal physical examination, particularly when breast cancer is more likely due to age or other risk factors.[2] However, for men with a suspicious physical examination, mammography is recommended due to its high sensitivity and specificity in distinguishing benign from malignant disease.[2]
The Mayo Clinic study by Hines et al. found that mammography added little information to the initial evaluation of men with breast symptoms, as breast cancer was typically suspected based on the presence of a dominant mass or other suggestive findings on clinical examination.[3] Furthermore, the study by Muñoz Carrasco et al. demonstrated that while mammography and ultrasound have high negative predictive values, their routine use in the absence of suspicious clinical findings may lead to unnecessary procedures.[4]
In summary, while imaging can be useful in certain clinical scenarios, such as when there is a suspicious mass or other concerning findings, it does not generally improve the assessment of breast cancer risk in cases of clinically benign gynecomastia. Clinical observation remains a reasonable approach in the absence of suspicious findings.

1.
Overuse of Imaging the Male Breast-Findings in 557 Patients.

Lapid O, Siebenga P, Zonderland HM.

The Breast Journal. 2015 May-Jun;21(3):219-23. doi:10.1111/tbj.12393.

Gynecomastia is the most common abnormality of the male breast. However, breast cancer may occur, albeit with a significantly lower incidence than in females. Imaging is often used as part of the diagnosis. The aim of this study was to assess the utilization and outcome of imaging with mammography or ultrasound of the male breast in a university hospital's department of radiology. A retrospective study assessing the imaging of the male breast in 557 patients over a 10-year period. Referral was done mainly by general surgeons and general practitioners. The most common indication was enlargement of the breast, described as gynecomastia or swelling in 74% of patients, followed by pain in 24% and "lumps" in 10%. The modalities used were mammography in 65%, ultrasound in 51% and both in 26%. Most examinations, 519, were BI-RADS 1 or 2, and 38 were BI-RADS 3 or higher. Altogether 160 patients had additional fine-needle aspiration or biopsy. Malignancies were diagnosed in five patients (0.89%). Imaging had a sensitivity of 80% and a specificity of 99%. The positive predictive value was 44% and the negative predictive value 99.8%. Malignancies are rare in the male breast. The probability of finding cancer when performing imaging of clinically benign findings in the male breast is negligible. Imaging is not warranted unless there are suspicious abnormalities. Routine imaging of gynecomastia should be discouraged.

2.
ACR Appropriateness Criteria Evaluation of The Symptomatic Male Breast.

Niell BL, Lourenco AP, Moy L, et al.

Journal of the American College of Radiology : JACR. 2018;15(11S):S313-S320. doi:10.1016/j.jacr.2018.09.017.

For men with an equivocal physical examination and of an age at which breast cancer is more likely, mammography or DBT is recommended as the initial imaging modality. Diagnostic mammography is useful in distinguishing malignancy from benign breast conditions in symptomatic males [, ]. A bilateral mammogram is routinely performed in symptomatic males [], although there is no literature comparing the efficacy of bilateral versus unilateral imaging. A bilateral examination may be useful to assess for symmetry [] and may detect asymptomatic contralateral gynecomastia or the rare nonpalpable contralateral carcinoma []. Although not routinely performed, pectoralis-displaced mammographic views can be acquired if the breast tissue is obscured by overlying well-developed pectoralis musculature [].
Mammography is highly sensitive and specific in distinguishing benign from malignant disease and is likely more sensitive than US at detecting breast cancer because microcalcifications may be optimally visualized on this modality [, ]. Studies demonstrate sensitivities ranging from 92% to 100%, specificities ranging from 90% to 96%, and negative predictive values (NPV) of 99% to 100% [, , , ]. Thus, mammography is useful both in identifying breast cancer and for obviating the need for US or biopsy in patients for whom the benign mammographic appearance confirms the clinical impression.

For men with a suspicious physical examination finding, mammography or DBT is recommended as the initial imaging study because mammography has high sensitivity, specificity, and NPV [, , , ]. Breast cancer in men typically presents with an irregular mass but may present as a focal asymmetry, asymmetry, or in association with calcifications [, , , ]. Because lobular development does not typically occur in men and men do not have the same background of benign proliferative changes as do women, relatively benign imaging findings, such as a circumscribed mass or round calcifications, should be considered suspicious in male patients [, , ].
Mammography is highly sensitive and specific in distinguishing benign from malignant disease and is likely more sensitive than US at detecting breast cancer because microcalcifications may be optimally visualized on this modality [, ]. Studies demonstrate sensitivities ranging from 92% to 100%, specificities ranging from 90% to 96%, and NPVs of 99% to 100% [, , , ]. Thus, mammography is useful both in identifying breast cancer and for obviating the need for US or biopsy in patients for whom the benign mammographic appearance confirms the clinical impression.

3.
The Role of Mammography in Male Patients With Breast Symptoms.

Hines SL, Tan WW, Yasrebi M, DePeri ER, Perez EA.

Mayo Clinic Proceedings. 2007;82(3):297-300. doi:10.4065/82.3.297.

Objective: To determine the contribution of mammography to the comprehensive clinical evaluation of men with breast symptoms.

Patients And Methods: We retrospectively reviewed the records of all men who underwent mammography between January 1, 2001, and December 31, 2004, at the Mayo Clinic In Jacksonville, Fla. Medical history, mammographic findings, and breast cancer diagnoses were assessed.

Results: A total of 198 men had 212 mammograms. Nine mammograms (from 9 different men) (4%) showed suspicious findings. Eight men underwent biopsy, which yielded a breast cancer diagnosis in 2 (1%). Of the 212 mammograms, 203 (96%) showed benign findings, including gynecomastia on 132 (62%). One patient with a benign-appearing mammogram later underwent breast biopsy, and malignant disease was diagnosed. All the men with breast cancer had a dominant mass on clinical examination and other findings suggestive of breast cancer. Of the 132 mammograms showing gynecomastia, 110 (83%) were from men who had taken predisposing medications or who had predisposing medical conditions.

Conclusions: Mammography added little information to the initial patient evaluation. Breast cancer may be suspected by the presence of a dominant mass. Gynecomastia can be predicted on the basis of the patient's symptoms or preexisting condition. Patients with suspicious findings on examination warrant appropriate clinical management regardless of mammographic findings. Mammography in men may be of benefit only for image guidance of percutaneous biopsy of a suspicious mass.

4.
Mammography and Ultrasound in the Evaluation of Male Breast Disease.

Muñoz Carrasco R, Alvarez Benito M, Muñoz Gomariz E, Raya Povedano JL, Martínez Paredes M.

European Radiology. 2010;20(12):2797-805. doi:10.1007/s00330-010-1867-7.

Objective: To assess clinical variables that may be useful in differentiating gynaecomastia from carcinoma and to analyse the contribution of mammography and ultrasound to the evaluation of male breast disease.

Methods: All men who underwent mammography and/or ultrasound between 1993 and 2006 in our hospital were retrospectively evaluated. Clinical characteristics in patients with gynaecomastia and those with carcinoma were compared. Radiological findings were classified according to the BI-RADS (Breast Imaging Reporting and Data System) criteria. The diagnostic performance of physical examination, mammography and ultrasound was determined and compared.

Results: A total of 628 patients with 518 mammograms and 423 ultrasounds were reviewed. The final diagnoses were: 19 carcinomas, 526 gynaecomastias, 84 other benign conditions and 25 normal. There were statistically significant differences in age, bilateral involvement, clinical presentation and physical examination between patients with carcinoma and those with gynaecomastia. The diagnostic performance of physical examination was lower than that of mammography and ultrasound (p < 0.05 for specificity). Mammography was the most sensitive (94.7%) and ultrasound the most specific (95.3%) for detection of malignancy (p > 0.05). We propose an algorithm for the use of mammography and ultrasound in men.

Conclusions: Mammography and ultrasound, with a negative predictive value close to 100%, make it possible to avoid very many unnecessary surgical procedures in men.