Please provide a dermatopathology interpretation of a skin biopsy from an adult with chronic unilateral or bilateral limb swelling due to lymphatic obstruction (e.g., post‑surgical, filarial, or venous insufficiency) suggestive of elephantiasis nostras verrucosa.

Dermatopathology Interpretation of Elephantiasis Nostras Verrucosa

The histopathologic findings in elephantiasis nostras verrucosa are surprisingly modest given the dramatic clinical appearance, showing pseudoepitheliomatous hyperplasia, dilated dermal lymphatic spaces, dermal fibrosis with fibroblast proliferation, and chronic inflammatory infiltrate. 1

Microscopic Features

Epidermal Changes

• Pseudoepitheliomatous hyperplasia is the hallmark epidermal finding, characterized by irregular acanthosis with downward proliferation of rete ridges that may mimic squamous cell carcinoma 1, 2
• Marked hyperkeratosis with overlying orthokeratotic or parakeratotic scale 1
• Papillomatosis contributing to the verrucous clinical appearance 1

Dermal Alterations

• Dilated lymphatic channels scattered throughout the dermis, representing the underlying lymphatic obstruction 1, 2
• Marked dermal fibrosis with proliferation of fibroblasts and collagen deposition 1, 2
• Chronic inflammatory infiltrate composed predominantly of lymphocytes and histiocytes, often perivascular in distribution 1, 2
• Fibrous tissue hyperplasia extending into the deeper dermis and potentially subcutaneous tissue 2

Critical Diagnostic Considerations

Rule Out Malignancy

• The pseudoepitheliomatous hyperplasia can closely mimic squamous cell carcinoma, making careful histologic examination essential to exclude true malignant transformation 1, 2
• No evidence of cytologic atypia, abnormal mitoses, or invasive growth should be present in benign elephantiasis nostras verrucosa 2
• If any suspicion of malignancy exists based on persistent hyperkeratosis, erosion, or atypical clinical features, additional biopsies are warranted 3

Distinguish from Infectious Etiologies

• Histologic examination should specifically exclude filarial organisms (microfilariae), which would indicate elephantiasis tropica rather than nostras 1
• Special stains or microbiologic studies may be needed to rule out deep fungal or atypical mycobacterial infections if clinical suspicion exists 3

Common Pitfalls in Interpretation

• Do not mistake pseudoepitheliomatous hyperplasia for squamous cell carcinoma—the absence of cytologic atypia and invasive architecture distinguishes benign reactive hyperplasia from true malignancy 1, 2
• The histologic findings are "moderately abnormal" and may seem disproportionately mild compared to the severe clinical deformity, which can lead to diagnostic uncertainty 1
• Superficial biopsies may miss the dilated lymphatic spaces in the deeper dermis, so adequate tissue depth is essential 1

Clinical Correlation Required

• The pathologist should receive clinical information about chronic lymphedema duration, underlying causes (venous insufficiency, post-surgical, obesity, recurrent cellulitis), and the characteristic "mossy foot" or cobblestone clinical appearance 1, 2
• History of recurrent bacterial lymphangitis (typically streptococcal) is common and contributes to progressive fibrosis, though the exact pathogenesis remains incompletely understood 4, 2
• Venous stasis alone does not produce the fibrotic nodular changes—recurrent infection or other inflammatory triggers appear necessary 2