Differential Diagnoses for Tender and Bruised Lumps in the Legs

Immediate Priority: Rule Out DVT

The American College of Chest Physicians recommends excluding deep vein thrombosis (DVT) using proximal compression ultrasound as the initial test, as this represents a life-threatening condition requiring immediate anticoagulation 1, 2, 3
Before attributing leg lumps to benign causes, DVT must be excluded, particularly when risk factors are present, such as recent immobilization, surgery, pregnancy, cancer, or previous DVT history 2, 3

The American College of Cardiology recommends performing proximal compression ultrasound (CUS) of the common femoral and popliteal veins as the initial test to exclude DVT 1, 3
If CUS is positive, initiate DVT treatment immediately without confirmatory venography 1, 3
If CUS is negative, perform D-dimer testing; if D-dimer is negative, no further testing is needed 1, 3
Consider whole-leg ultrasound in patients unable to return for serial testing or with severe calf symptoms 1, 3

The American College of Cardiology suggests that colchicine is preferred when erythema nodosum is the dominant lesion 4
Subcutaneous Panniculitis-like T-cell Lymphoma presents as solitary or multiple subcutaneous nodules to indurated plaque-like lesions, often with a "bruise-like aspect" with CD4+/CD56+ phenotype, and requires biopsy for definitive diagnosis with immunophenotyping 5, 6
Venous Claudication/Post-thrombotic Syndrome presents with tight, bursting pain in entire leg, worse in calf, associated with edema and signs of venous stasis, and history of iliofemoral DVT is characteristic 7
Symptomatic Baker's Cyst presents with swelling and tenderness behind knee extending down calf, pain present both with exercise and at rest, and is not intermittent in nature 7
Primary cutaneous diffuse large B-cell lymphoma (leg type) presents as red to bluish-red tumors, particularly in elderly patients on legs, and biopsy is essential showing CD20+, CD79a+, BCL2+, BCL6+, MUM-1+, FoxP1+ 5, 6

Never assume "just a bruise" without excluding DVT when swelling seems disproportionate to injury mechanism, as recommended by Praxis Medical Insights 2
Leg ulcers in patients with tender lumps may indicate vasculitis, requiring systemic treatment rather than local measures, according to the Annals of the Rheumatic Diseases 4
Bruise-like appearance can represent hematologic malignancy (CD4+/CD56+ hematodermic neoplasm or lymphoma) requiring urgent biopsy, as suggested by the Annals of Oncology 5, 6