Squamous intraepithelial lesions (SILs) of the larynx, clinically usually defined as leukoplakia and chronic laryngitis, have remained the main controversial topic in laryngeal pathology for decades as regards classification, histological diagnosis and treatment. SILs are caused by smoking and alcohol abuse. There is also mounting evidence that gastroesophageal reflux is a potential aetiological factor. Human papillomavirus infection seems to play little if any role in laryngeal carcinogenesis. Histological classification of SILs is the central disputed aspect of these lesions. There are as yet no generally accepted criteria for histological grading of laryngeal SILs. Three currently used classifications of SILs are reviewed here: the dysplasia system, the Ljubljana classification and the binary system of squamous intraepithelial neoplasia. One of the most important issues of SILs is the risk of malignant transformation. Data in the literature are controversial because of inconsistent use of morphological criteria in different classifications. It is often difficult for clinicians to agree on the most appropriate therapeutic option for a particular grade of SIL that has been diagnosed. Transition from normal epithelium to SILs and squamous cell carcinoma is related to progressive accumulation of genetic changes leading to a clonal population of transformed epithelial cells. Despite extensive research into these genetic changes in laryngeal carcinogenesis, reliable genetic markers with diagnostic and prognostic value are still lacking.

Objectives: The immunohistochemical phenotype, distribution and significance of proliferation of myofibroblasts in laryngeal epithelial hyperplastic lesions (EHL) and squamous carcinoma (SC) were analyzed. Methods: Samples of 42 resected larynxes and 40 laryngeal biopsies of EHL and SC were included. Immunohistochemistry was performed using antibodies against vimentin, α-smooth muscle actin (SMA), desmin and leukocyte common antigen. Results: Myofibroblasts were vimentin- and SMA-positive, and were found exclusively in SC, indicating that invasion beyond the basement membrane is necessary to evoke a myofibroblastic stromal reaction. We observed two patterns of stromal reaction in SC: one was characterized by a marked proliferation of myofibroblasts and desmoplasia, with scarce lymphocytic infiltration; this pattern tended to be associated with well- or moderately differentiated SC. The other was characterized by few myofibroblasts, weak desmoplasia, and dense lymphocytic infiltration; the latter pattern tended to be associated with moderately or poorly differentiated SC. The degree of myofibroblast proliferation was inversely related to the density of lymphocytic infiltration. Antibodies against SMA also stained stromal blood vessels, demonstrating a gradual increase of vessel density as the grade of EHL increased. Conclusions: Immunohistochemical analysis of myofibroblasts provides useful information on the phenotypic characteristics of the stroma in laryngeal EHL and SC, and can serve as an additional marker of invasion.

A retrospective morphologic and immunohistochemical study of 25 benign and 5 malignant laryngeal hyperplastic lesions was performed concerning a local immune response which might be characteristic and of prognostic value for each particular group of these alterations, using Kambic’s classification, especially for precancerous and cancerous lesions. On paraffin and frozen sections, 7 monoclonal antibodies against various leukocytic antigens were used. CD43 and CD45RO T lymphocytes were the predominant cells in the infiltrates, and their frequency increased according to the degree of hyperplastic lesions. Next in frequency were CD4 cells, and a predominance of CD4 over CD8 cells was an obvious finding. The infiltration of CD68-, CD57-, and CD20-positive cells was generally weak. The intensity and composition of the local reaction in all cases of atypical hyperplasias was nearly identical, regardless of their subsequent behaviour. No apparent cytotoxic effects on the epithelial cells, either in precancerous or in cancerous lesions, were observed. Thus, the immunocompetent cells in the epithelial and stromal tissue are most likely not an effective defense in preventing hyperplastic lesions from becoming malignant. It seems that laryngeal hyperplastic lesions do not provoke an essential defense immune response, but the present local inflammatory reaction might be a constituent part of etiologically different inflammations which may lead to unfavorable lesions.

Molecular, histopathological, and clinical studies were carried out on a series of 79 laryngeal papillomas (LP) from 36 patients in order to investigate the hypothesis that juvenile and adult LP may represent a biological entity causally related to Human papilloma virus (HPV) infection. Using in situ hybridization with biotin-labelled probes and polymerase chain reaction, we detected human papilloma virus (HPV) 6/11 in 28 of 29 juvenile LP, in 26 of 30 adult multiple, and in 17 of 20 adult solitary LP. None of LP was found to harbour HPV types 16, 18, 31, 33, and 51. There were no clear-cut histological differences between juvenile and adult LP, the presence of koilocytosis was equally observed in both, and there was no prevalent type of epithelial hyperplasia in either form, except that all three cases of atypical hyperplasias (precancerous lesions) were found among adult patients. During a 14 year follow-up, no carcinomatous transformation of LP was observed. All juvenile LP in our study had frequent recurrences of the disease, however, numerous surgical procedures were also required in 16 of 27 adult patients. Our study supports Lindeberg's hypothesis of a similar pathogenesis for all forms of LP caused by the HPV types 6/11.

The purpose of the present study was to evaluate the biological behaviour of the marginal epithelium, that proliferates and eventually covers laryngeal granulomas, and to reveal the applicability of the recently re-introduced Ljubljana classification when reporting reactive epithelial hyperplastic lesions. A retrospective clinical and histomorphological analysis was performed on 149 laryngeal granuloma biopsies. Epithelial changes were classified according to the Ljubljana classification into normal epithelium; simple, abnormal, or atypical hyperplasia; and carcinoma in situ. Atrophic epithelium, not evaluated separately in the Ljubljana classification, was additionally assessed. Simple hyperplasia was found in 98 cases (65.8 per cent), abnormal hyperplasia in seven (4.7 per cent), atrophic epithelium in 24 (16.1 per cent), and normal squamous epithelium in 20 (13.4 per cent). Atypical hyperplasia and carcinoma in situ were not observed. The results of our study clearly showed that the proliferation of the covering epithelium mostly in the form of simple hyperplasia, is entirely reactive and therefore reversible. No epithelial hyperplastic lesions were found that were previously described to be associated with an increased risk of malignant alteration, namely atypical hyperplasia and carcinoma in situ. However, since an initial growth of an invasive malignant neoplasm might macroscopically imitate the appearance of laryngeal granuloma, a histological examination in all aetiological forms of laryngeal granulomas is required. By clearly discerning the benign nature of epithelial changes in laryngeal granulomas, the recently re-evaluated and further formulated Ljubljana classification may also influence the clinical handling of patients.