ORIGINAL ARTICLESilver-stained organizer regions and immunoglobulins in cutaneous keratoacanthomas and squamous cell carcinomas
Introduction
Keratoacanthomas (KAs) are highly differentiated, biologically benign, non-metastasizing tumors characterized by rapid development and a tendency towards spontaneous regression [16]. Usually, the tumor develops in three stages [25], [37]. The early phase of proliferation is often difficult to distinguish histologically from squamous cell carcinoma (SCC) because high mitotic activity is observed, the degree of keratinization is still low, and nuclear atypia is common. The fully developed lesion is normally diagnosed more easily and is followed by the phase of involution with frequent detection of apoptotic cells. Invasive SCCs are also epidermal neoplastic lesions consisting of altered keratinocytes. However, it remains unclear whether the alteration of neoplastic cells in both disorders involves different inflammatory reactions and the production of immunoglobulins (Igs) [4], and whether the infiltration of reactive cells is secondary to the underlying disease or rather an active participant in determining the outcome of the neoplasia. Nucleolar organizer regions (NORs) are loops of DNA situated on the short arms of acrocentric chromosomes 13, 14, 15, 21, and 22. They can be demonstrated in formalin-fixed, paraffin-embedded sections by a one-step silver technique, the resulting black structures being termed AgNORs [2], [19], [21]. The aim of the study was to investigate the biological activity of epidermal cells in KAs and SSCs by counting the number of silver-stained NORs, to estimate the quantity of Ig-producing cells and the inflammatory cellular infiltrate (ICI) in these entities, and to make a comparative evaluation of Ig-producing cells and AgNORs in order to identify any possible mutual correlation among the expression of these parameters.
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Material and methods
Firstly, 88 cases of KA excised under local anesthesia were studied. Tumors were evaluated according to the clinical picture and history, as well as to the histological characteristics of the lesion. The histological diagnosis of KA and its differentiation from SCC were based on the microscopic features and special stains, PAS with or without prior amylase digestion, and elastic fibers stain (Shikata's orcein method). The three stages of KA evolution were defined in accordance with the
Results
In all 30 cases of KA, intraepithelial elastic fibers and an abundant amount of epithelial glycogen were detected. Table 1 depicts the number of AgNORs and the proportion of immunocytes producing IgG, IgA, IgM, and IgE, as well as the degree of ICI in the three stages of the tumor. All cases of KA examined had a mean number of 1.727 AgNORs (S.D. 0.232). The scatter diagram (Fig. 2) demonstrates the distribution of AgNORs in the neoplasm. The statistical processing of the results, made by using
Discussion
KA consists of a neoplasm of unknown origin with a specific clinical behavior and histological picture. Some investigators consider it a distinct type of SCC with a benign attitude that, in some cases, may become malignant [28]. Others suggest that some types of SCC may be similar to the various stages of KA clinically and histologically [35]. The amount of glycogen in cutaneous KA is reported to be significantly greater than that observed in SCC arising in solar keratosis, and intraepithelial
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