Ann Dermatol.  2016 Aug;28(4):427-432. 10.5021/ad.2016.28.4.427.

Histopathological Differential Diagnosis of Psoriasis and Seborrheic Dermatitis of the Scalp

• Park JH
• Park YJ
• Kim SK
• Kwon JE
• Kang HY
• Lee ES
• Choi JH
• Kim YC

• KMID: 2344811
• DOI: http://doi.org/10.5021/ad.2016.28.4.427

Abstract

BACKGROUND
The differential diagnosis of psoriasis and seborrheic dermatitis can be difficult when both conditions are localized to the scalp without the involvement of other skin sites.
OBJECTIVE
We aimed to evaluate the histopathological differences between psoriasis and seborrheic dermatitis on the scalp and identify favorable criteria for their differential diagnosis.
METHODS
We evaluated 15 cases of psoriasis and 20 cases of seborrheic dermatitis of the scalp that had been clinicopathologically diagnosed. Skin biopsy sections stained with H&E were examined. Additional immunohistochemistry was performed, including Ki-67, keratin 10, caspase-5, and GLUT-1.
RESULTS
On histopathological examination, mounds of parakeratosis with neutrophils, spongiform micropustules of Kogoj, and clubbed and evenly elongated rete ridges were significantly more frequently observed in psoriasis. Follicular plugging, shoulder parakeratosis and prominent lymphocytic exocytosis were significantly more common in seborrheic dermatitis. Moreover, significantly higher mitotic figures were observed in psoriatic lesions than in seborrheic dermatitis. Immunohistochemistry did not show any difference between psoriasis and seborrheic dermatitis.
CONCLUSION
Histopathological features favoring psoriasis include mounds of parakeratosis with neutrophils, spongiform micropustules of Kogoj, clubbed and evenly elongated rete ridges, and increased mitotic figures (≥6/high-powered field). Features indicating seborrheic dermatitis are follicular plugging, shoulder parakeratosis and prominent lymphocytic exocytosis. Immunohistochemistry was not helpful in differentiating psoriasis from seborrheic dermatitis.

Keyword

Differential diagnosis; Psoriasis; Scalp; Seborrheic dermatitis

MeSH Terms

Biopsy
Dermatitis, Seborrheic*
Diagnosis, Differential*
Exocytosis
Immunohistochemistry
Keratin-10
Neutrophils
Parakeratosis
Psoriasis*
Scalp*
Shoulder
Skin
Keratin-10

Figure

• 

  Fig. 1 Clubbed and even lengths of rete ridges were more common (A) in psoriasis than (B) in seborrheic dermatitis. Follicular plugging and shoulder parakeratosis were less common (C) in psoriasis than (D) in seborrheic dermatitis (H&E; A~D, ×200).

• 

  Fig. 2 Most cases showed basal layer-dominant GLUT-1 staining patterns in the psoriasis (93.3%; A) and seborrheic dermatitis (70.0%) groups. Although the proportion of diffuse pattern GLUT-1 distribution was higher in seborrheic dermatitis (B), the difference was not statistically significant (p=0.199; immunohistochemical GLUT-1 expression, ×400).

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