Histopathologic features distinguishing secondary syphilis from its mimickers

Area of Science:

• Dermatopathology
• Infectious Disease Histology

Background:

• Syphilis diagnosis can be challenging due to clinical mimicry.
• Biopsy and histopathologic examination are often necessary for definitive diagnosis.

Purpose of the Study:

• To identify key histopathologic features differentiating secondary syphilis from pityriasis lichenoides (PL), pityriasis rosea (PR), and early mycosis fungoides (MF).

Main Methods:

• Comparative histopathologic analysis of 100 syphilis cases against 110 PL, 72 PR, and 101 MF cases.
• Evaluation of specific features including rete ridge elongation, inflammation patterns, and cellular morphology.

Main Results:

• Elongated rete ridges and interstitial inflammation suggest syphilis over PL, but overlap exists.
• Secondary syphilis can be differentiated from PR by neutrophils in the stratum corneum, plasma cells, and specific interface dermatitis.
• Plasma cells and lymphocytes with abundant cytoplasm are rare in early mycosis fungoides, aiding differentiation.

Conclusions:

• Histopathologic features of syphilis can overlap with PL, PR, and early MF, necessitating a high index of suspicion.
• Distinguishing syphilis from PL histologically is difficult; features like vacuolar interface dermatitis are observed in both.
• While plasma cells and rete ridge elongation favor syphilis, their presence in other conditions complicates definitive diagnosis without clinical correlation.