Ingrown toenail: histopathologic and immunohistochemical study.

Area of Science:

• Dermatopathology
• Histopathology

Background:

• Ingrown toenail (IT) is a common condition with poorly documented morphologic alterations.
• Understanding IT's histopathology is crucial for accurate diagnosis and management.

Purpose of the Study:

• To investigate the detailed morphologic and immunohistochemical changes in ingrown toenail (IT).
• To correlate these changes with clinical staging and differentiate IT from malignancy.

Main Methods:

• Analysis of 14 IT biopsies using routine histology, histochemical stains (Masson trichrome, PAS, Gram), and immunohistochemistry (MIB-1, p63, D2-40, AE1-AE3).
• Clinical classification of patients into four stages (1, 2a, 2b, 3).

Main Results:

• Key findings include epithelial ingrowing (matrix/hyponichium) and chronic inflammation with vascularization, varying by stage.
• Advanced stages (2b, 3) showed prominent changes and epithelial dyskeratosis, mimicking well-differentiated squamous cell carcinoma.
• MIB-1 expression was limited to basal/parabasal cells; p63 was highly expressed by epithelial nests.

Conclusions:

• Ingrown toenail (IT) presents with epithelial ingrowing and granulation tissue, with complexity increasing with clinical stage.
• Advanced IT can resemble squamous cell carcinoma, but MIB-1 is not a reliable differentiator.
• High p63 expression in IT epithelium does not indicate malignancy and should not lead to misdiagnosis.