Histopathological Features of Erythema Annulare Centrifugum
Erythema annulare centrifugum (EAC) is classified histopathologically into two distinct types—superficial and deep—with the superficial type being far more common (78% of cases) and characterized by a tight perivascular lymphocytic infiltrate in the superficial dermis with overlying parakeratosis and spongiosis, while the deep type shows a dense perivascular and periadnexal lymphocytic infiltrate ("coat-sleeve" pattern) in the mid-to-deep dermis without epidermal changes. 1
Superficial Type (Most Common - 78% of Cases)
The superficial variant demonstrates the following key features 1:
- Tight perivascular lymphocytic infiltrate confined to the superficial (papillary) dermis surrounding dilated capillaries 1
- Epidermal changes including parakeratosis (abnormal retention of nuclei in the stratum corneum) and spongiosis (intercellular edema) 1
- Scaling clinically correlates with the parakeratotic epidermis seen histologically 1
Deep Type (Less Common - 22% of Cases)
The deep variant shows distinct histological patterns 1:
- Dense perivascular and periadnexal lymphocytic infiltrate in the mid-to-deep reticular dermis, creating the characteristic "coat-sleeve" or "cuffing" pattern around vessels and adnexal structures 1
- Absence of epidermal changes—no parakeratosis or spongiosis, which explains the lack of scale clinically in this variant 1
- Deeper dermal involvement extending well below the papillary dermis 1
Important Diagnostic Considerations
The diagnosis of EAC should prompt re-evaluation because recent evidence demonstrates that "EAC" functions as a clinical reaction pattern rather than a specific disease entity, with 78% of cases actually representing other conditions including lupus erythematosus (32%), spongiotic dermatitides (28%), or pseudolymphoma (18%). 2
Critical Pitfall to Avoid
When encountering a histological pattern labeled as "EAC," consider these alternative diagnoses 2:
- Tumid lupus erythematosus (32% of cases clinically diagnosed as EAC)—look for mucin deposition and deeper dermal lymphocytic infiltrates 2
- Spongiotic dermatitis (28% of cases)—distinguished by prominent spongiosis and eosinophils 2
- Pseudolymphoma/cutaneous Lyme disease (18% of cases)—in pseudolymphomatous patterns, spirochetes were identified in 81% of cases by focus-floating microscopy and confirmed by Borrelia-specific PCR in 67% 2
Additional Histological Clues
The histopathological examination should specifically assess 2:
- Mucin deposition (suggests lupus erythematosus rather than true EAC) 2
- Eosinophils in the infiltrate (points toward spongiotic dermatitis) 2
- Spirochetes using focus-floating microscopy or Borrelia PCR if pseudolymphomatous pattern is present, as this may represent cutaneous Lyme disease 2
Clinical-Pathological Correlation
The presence or absence of scale clinically correlates directly with histological type 1: