Chest Lump: Differential Diagnosis for a Small Blue Nodule

A small blue lump on the chest warrants clinical evaluation. Differential includes:

Benign Lesions

• Blue nevus: Melanocytic, deep dermal pigment → blue-black dome; benign but biopsy if changing.
• Venous lake: Compressible, dark blue papule (dilated venule); common on sun-exposed skin.
• Dermatofibroma: Firm, dimples on pinch; usually brown but can be bluish.
• Epidermoid cyst: Mobile, central punctum; may appear bluish if inflamed.
• Lipoma: Soft, mobile, subcutaneous; usually skin-colored.

Vascular / Hematologic

• Hemangioma: Bright red-purple; blanchable.
• Angiokeratoma: Dark red-blue, keratotic.
• Bruise (ecchymosis): Evolving colors; history of trauma.

Concerning Features (Biopsy Indicated)

• Rapid growth, ulceration, bleeding
• Irregular borders, color variegation
• Size >6 mm
• Patient >50, immunosuppressed
• Melanoma (nodular, amelanotic), Merkel cell, Kaposi sarcoma, metastatic deposit.

Workup

1. Dermoscopy (vascular patterns, pigment network).
2. Excisional/incisional biopsy for histology.
3. Imaging if deep/large or nodal concern.