Historical Background, Terminology, and Classification
The concept of pseudocarcinosis (pseudocancerosis) is customarily considered to go back to Unna (1894) who was the first to note that the excessive proliferation of epidermis seen in lesions of lupus vulgaris may resemble squamous cell carcinoma of the skin, Unna did not find any metastases in his patients, even though the disease was of long standing. It is difficult to say in retrospect whether or not the epidermal hyperplasia observed by him was benign, although atypical, because he did not follow up the patients and because no criteria were available at that time by which inflammatory hyperplasia of the epidermis can be differentiated clinically and histologically from squamous cell carcinoma. His observations did, however, attract the attention of dermatologists to so-called atypical epidermal growths. The first to study these was Friedländer (1877) who showed that atypical epidermal proliferation was not always a sign of malignancy and that it could occur in a variety of conditions including, among others, lupus vulgaris, leprosy, fistulas, and elephantiasis. Friedländer came to the conclusion that while every atypical epidermal growth should not be regarded as necessarily cancerous, every cancer represents atypical epidermal growth. Although more than a hundred years have passed since the publication of Friedländer’s book, the issues raised there still remain of current interest today.
KeywordsSquamous Cell Carcinoma Pyoderma Gangrenosum Cutaneous Squamous Cell Carcinoma Epidermal Hyperplasia Seborrheic Keratosis
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