Is This Case Consistent with Pityriasis Lichenoides Chronica?
Based on the histopathological features you've described, this case is highly consistent with Pityriasis Lichenoides Chronica (PLC). The key diagnostic features align well with established histopathological criteria for this condition.
Core Histopathological Features Supporting PLC Diagnosis
The diagnosis of PLC rests on several characteristic histopathological findings that appear to match your case description:
Essential Microscopic Features Present in PLC
- Vacuolar changes and necrotic keratinocytes are present in virtually 100% of PLC cases, representing a pathognomonic feature 1
- Both superficial and deep lymphocytic infiltrates occur in 99% of cases, creating the characteristic "T-shaped" periadnexal arrangement along follicular and sudoral epithelia 1
- Basal cell vacuolation with perivascular infiltrate is seen universally in confirmed PLC cases 2
- Infiltration of lymphocytes into the adnexal epithelium (adnexotropism) occurs in 97% of cases and is a highly valuable diagnostic feature 1
Additional Supporting Features
- Superficial perivascular and/or intraepidermal red blood cells are observed in 83% of PLC cases 1
- Exocytosis is present in approximately 45% of cases 2
- The inflammatory cells are characteristically small- to medium-sized lymphocytes without eosinophilic infiltrates 1
Critical Diagnostic Distinction
A key differentiating point: PLC is NOT a true lymphocytic vasculitis. While perivascular infiltrate is universal, blood vessel damage and fibrinoid deposition in vessel walls are absent in PLC 2. This distinguishes it from PLEVA (the acute variant), where lymphocytic vasculitis is present in all cases, though still without fibrinoid deposition 2.
Clinical Correlation Required
The histopathological diagnosis should be confirmed with clinical features:
- Chronic course with papulosquamous lesions showing remissions and exacerbations 2
- Distribution pattern typically on trunk and extremities, though rare presentations including palmoplantar involvement can occur 3
- Age distribution most commonly affects patients in their second decade, though can occur at any age 2
Common Diagnostic Pitfalls to Avoid
- Do not confuse with psoriasis, especially in atypical presentations like palmoplantar involvement where clinical mimicry can occur 3
- Rule out cutaneous T-cell lymphoma, as the presence of atypical lymphocytes requires careful evaluation, though PLC lymphocytes are small-to-medium sized rather than large and pleomorphic 1
- Distinguish from other papulosquamous disorders through the characteristic deep dermal infiltrate with adnexal involvement, which is relatively specific to PLC 1
The histopathological pattern you describe strongly supports PLC diagnosis, particularly if it demonstrates the characteristic deep lymphocytic infiltrate with adnexotropism and absence of true vasculitis.