A painful lump has developed under my armpit—what department should I visit?

A small, painless, and non-itchy lump under the arm is commonly caused by a lipoma. Lipomas frequently occur in areas such as the axilla (armpit), neck, shoulders, upper arms, thighs, and buttocks. They typically present as one or more painless, subcutaneous masses.

Which department should I visit if a small, painful lump appears under my arm?

If a small, painful lump develops under the arm, patients are advised to consult a general surgeon. Painful axillary lumps are most commonly attributable to one of the following two conditions:

1. Lymphadenitis: This condition manifests as a tender, painful lump under the arm, often with localized tenderness upon palpation. It usually results from the spread of infection from the upper limb or chest wall to the axillary lymph nodes. Patients should seek evaluation by a general surgeon.

2. Infected sebaceous cyst: A sebaceous cyst is a benign, superficial soft-tissue mass that protrudes above the skin surface of the axilla. When infected, it becomes markedly painful and tender, and may even progress to abscess formation. Patients should consult a general surgeon for ultrasound examination to confirm the diagnosis. Once either of these two conditions is confirmed, appropriate treatment—including anti-inflammatory therapy or surgical intervention—can be initiated.

Breast cancer may also involve the axillary region, leading to painless axillary masses. If such a symptom occurs, prompt evaluation and surgical resection for breast cancer are recommended to alleviate discomfort and restore health.

Accessory breasts (polymastia) are broadly classified into two types: complete and incomplete accessory breasts. Regardless of type, either may involve the axillary region, causing abnormal symptoms such as swelling or bulging under the arm.

We hope the above information is helpful. Wishing you good health and happiness!