What is the differential diagnosis for a 37-year-old female with a 1-week history of unilateral breast pain, a history of breast reduction surgery, and no other risk factors, presenting with symmetrical breasts and no signs of mass, lymphadenopathy, or inflammation?

Differential Diagnosis for Unilateral Breast Pain Post-Breast Reduction

In a 37-year-old woman with unilateral breast pain one week after breast reduction surgery and normal clinical examination, the differential diagnosis should prioritize post-surgical causes including nerve regeneration pain, scar tissue formation, and focal nerve injury, followed by noncyclical mastalgia of inflammatory origin, musculoskeletal causes, and less commonly, complex regional pain syndrome.

Post-Surgical Causes (Most Likely Given History)

Nerve-Related Pain

• Postsurgical pain may result from nerve regeneration, focal nerve injury due to ischemia, or scar pain, particularly if the surgeon cut across Langer lines of tension or if there was postoperative infection or hematoma 1
• Chronic postoperative pain occurs in approximately 20% of patients after reduction mammaplasty, with 7% experiencing moderate to severe pain 2
• More than half of post-reduction mammaplasty pain is compatible with neuropathic pain, characterized by burning, shooting, or electric-like sensations 2
• Young age and complications during surgery are significantly related to developing persistent pain after breast reduction 2

Complex Regional Pain Syndrome (CRPS)

• Although rare, CRPS can occur after breast reduction surgery and presents with devastating pain, swelling, and cutaneous temperature changes due to vasomotor dysfunction from abnormal sympathetic loop reflex 3
• This condition should be considered when pain is disproportionate to clinical findings and persists beyond expected healing time 3

Noncyclical Mastalgia (Primary Differential)

Inflammatory/Idiopathic Causes

• Noncyclical breast pain accounts for 25% of breast pain cases, is typically unilateral and focal, and is predominantly inflammatory rather than hormonal in origin 1, 4
• This type occurs more commonly in women in their fourth decade (30s-40s), making it age-appropriate for this patient 1
• The pain is often precisely localizable and reproducible, commonly located in the subareolar area or lower inner breast 1, 4
• Noncyclical mastalgia has spontaneous resolution in up to 50% of patients and does not respond well to hormonal manipulation 1

Infectious/Inflammatory Conditions

• Mastitis or breast abscess can present with focal pain that may precede visible signs of induration, redness, warmth, and fever 1, 4
• Mondor disease (thrombophlebitis of the thoracoepigastric vein) can present as breast pain, sometimes with a palpable cord 1, 4

Extramammary Causes

Musculoskeletal Origins

• Costochondritis (Tietze syndrome) can cause referred pain to the breast and is reproducible with chest wall palpation 4, 5
• Muscle strains or intercostal nerve irritation (T3-T5 anterior lateral and medial branches) can manifest as breast or nipple pain 4
• These causes should be strongly considered when breast examination is entirely normal 5

Less Likely but Important Considerations

Cyclical Mastalgia

• Cyclical pain represents 70% of all breast pain cases but is typically bilateral or diffuse, waxing and waning with the menstrual cycle 6, 4
• Given the unilateral and non-diffuse presentation in this case, cyclical mastalgia is less likely but cannot be completely excluded 1
• The pain would be most pronounced in the luteal phase if hormonal in origin 1, 5

Malignancy (Low Probability)

• The risk of cancer in women presenting with breast pain as the only symptom ranges from 1.2-6.7%, and is extremely low with cyclical pain alone in the absence of other signs 6, 5
• Some cancers, particularly invasive lobular and anaplastic carcinomas, can present with pain, making proper evaluation essential 6
• However, with symmetrical breasts, no mass, no lymphadenopathy, and no inflammation on examination, malignancy is unlikely 1

Clinical Approach Algorithm

Immediate Assessment

1. Determine if pain is related to menstrual cycle (cyclical vs. noncyclical) 4
2. Assess for reproducible chest wall tenderness to identify musculoskeletal causes 4, 5
3. Evaluate surgical site for signs of nerve injury patterns (burning, shooting pain suggests neuropathic origin) 2

Imaging Considerations

• For focal, noncyclical breast pain in a 37-year-old, diagnostic mammogram with ultrasound is recommended to exclude underlying benign or malignant lesions 6, 7
• Cyclical, diffuse breast pain with normal examination does not require imaging beyond routine age-appropriate screening 4, 5
• Given the post-surgical history and focal nature, imaging is warranted in this case 1, 7

Common Pitfalls to Avoid

• Do not dismiss breast pain without proper evaluation, as some cancers can present with pain alone 6, 5
• Do not fail to consider extramammary causes when breast examination and imaging are normal 6, 5
• Do not overlook post-surgical neuropathic pain, which may require specific management strategies different from typical mastalgia 2
• Recognize that pain one week post-surgery may represent normal healing, but persistent or severe pain warrants investigation for complications 2, 3