Dermatology Journal Scan / Research · December 19, 2022 Understanding the Malignant Transformation of Seborrheic Keratosis

Abstract 

Seborrheic keratosis is a common benign neoplasm composed of basaloid keratinocytes. However, little is known about the malignant transformation of the tumor. Eleven cases of seborrheic keratosis with malignant transformation were analyzed. The 11 patients included 5 male patients and 6 female patients with a median age of 75 years at diagnosis (68-90 years). The tumors arose at various sites from the scalp (n = 3) to the lower leg (n = 2). The median tumor size was 12 (10-32) and 40 (20-75) mm in 7 noninvasive and 4 invasive cases, respectively. One patient exhibited in-transit skin metastasis. Histopathology of the malignant components resembled porocarcinoma or inverted follicular keratosis. Bowenoid and pagetoid spreading was frequently observed. The malignant components expressed cytokeratin 5/6 (100%) and GATA3 (73%), but not cytokeratin 7 (0%), cytokeratin 19 (9%), BerEP4 (0%), c-kit (0%), and NUT (0%). No significant immunoreactivity of YAP1 was observed in any of the cases. Mutant-type immunostaining of p53 and PTEN was observed in 91% and 82% of the cases, respectively. An increase in p16 expression was seen in 6 (86%) of the 7 cases with noninvasive carcinoma, although a loss of p16 immunoexpression was seen in the invasive carcinoma component in 3 (75%) of the 4 cases. This study demonstrated that seborrheic keratosis can undergo malignant transformation, particularly in large-sized lesions in elderly patients. Malignant components mimic porocarcinoma or inverted follicular keratosis. Malignant transformation induced by TP53 and PTEN mutations and tumor invasion by CDKN2A inactivating mutations are suggested in this study.

The American Journal of Dermatopathology

Seborrheic Keratosis With Malignant Transformation (Invasive or Noninvasive Squamous Cell Carcinoma Arising in Seborrheic Keratosis): A Clinicopathologic and Immunohistochemical Study of 11 Cases

Am J Dermatopathol 2022 Dec 01;44(12)891-899, K Goto, K Ogawa, T Hishima, N Oishi, O Tomita, T Tsuyuki, T Oda, Y Iwahashi, Y Inaba, K Honma 

TAKE-HOME MESSAGE

• This study comprising 11 cases details the clinicopathologic characteristics of patients with malignant transformation of a seborrheic keratosis. All lesions contained both a component of squamous cell carcinoma and seborrheic keratosis that was most commonly classified as acanthotic or reticulated. Immunohistochemical evaluation helps differentiate the malignant transformation of a seborrheic keratosis from porocarcinoma.
• This article provides insight into the characteristics associated with the malignant transformation of a seborrheic keratosis.

–  Joshua R. Ortego, MD

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Benjamin Hidalgo-Matlock
Skin Care Physicians of Costa Rica

Clinica Victoria en San Pedro: 4000-1054
Momentum Escazu: 2101-9574

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