Comparison of following grading systems for laryngeal dysplasia.
Abstract
Leukoplakia is a clinical term referring to a whitish plaque on the mucosal surfaces that cannot be scraped off. Otolaryngologists daily have to face such findings in both the oral cavity and the larynx. In the latter, several pathological conditions ranging from reactive to neoplastic lesions can underlie leukoplakia. Hence, a proper understanding of the histological spectrum of laryngeal diseases sharing leukoplakia as their main clinical presentation plays a critical role in the clinical management of patients. In that setting, the histological assessment of laryngeal dysplasia is known to have represented a matter of disagreement mostly about grading, and several grading systems have been proposed over time. Nonetheless, the histologic assessment of laryngeal leukoplakia is a mandatory requirement in clinical planning, leading to a proper treatment choice.
Keywords
- leukoplakia
- dysplasia
- larynx
- grading
- differential diagnosis
1. Introduction
Laryngeal leukoplakia (LL) is a clinical term referring to the presence of a whitish plaque on mucosal membranes that cannot be scraped off [1]. Leukoplakia is a descriptive term having not a single histological counterpart but, on the contrary, a broad spectrum of pathological pictures, ranging from benign (reactive-inflammatory) lesions to dysplastic and neoplastic conditions. Establishing a proper diagnosis represents a unique challenge since the optimal clinical management depends on the identification of the reactive or dysplastic nature of that lesion. LL can be found at any laryngeal site, mostly onto the true vocal folds. Regardless of the clinical presentation, LL should be histopathologically examined to rule out both dysplasia and invasive carcinoma, which should be properly treated. Further complexity in managing LL relies on the frequent location along the vibratory side of the vocal folds, where scarring could produce functional consequences and voice quality impairment. Mucosal biopsies performed with flexible laryngoscope represent to date the most widely used diagnostic technique to obtain an earlier diagnosis. Early detection is the strongest prognostic factor affecting the patients’ survival. However, the biopsy technique has some limitations, as mucosal sampling could underestimate the severity of the lesion first because of the poor depth of biopsy, then because of the histological heterogeneity of broader lesions [2, 3].
2. Histopathological assessment
2.1 Vocal folds’ normal anatomy and histology
The true vocal folds are laryngeal structures consisting of both vocalis muscle and vocal ligament, covered by stratified squamous epithelium. The free edge is formed by the vocal ligament and its epithelial lining, representing the mobile top of the vocal folds and contributing to phonation. The vocal ligament is in continuity with the cricovocal (cricothyroid) ligament, extending from the thyroid cartilage to the vocal process of the arytenoid cartilages. The vocalis muscle lies laterally to the vocal ligament, extending from the vocal process of the arytenoids to the vocal ligament [4]. The true vocal folds are lined by nonkeratinized stratified squamous epithelium, as seen in the superficial rim of the ary-epiglottic folds, in the anterior epiglottic surface (Figure 1). In contrast, ventricle, ventricular folds, saccule, and subglottis are covered by ciliated columnar epithelium, with scattered goblet cells. Seromucinous glands can be found in small clusters within the loose stroma of the false vocal fold, whereas they are scattered in the lamina propria of ventricle, saccule, posterior epiglottic surface, subglottis. Seromucinous glands are usually scanty or absent in the true vocal folds [5]. The false vocal fold has no contractile structures, is covered by respiratory-type epithelium, and represents the upper limit of the ventricle, whereas the true vocal fold is the lower limit.
2.2 Histopathology
LL is an
3. Laryngeal leukoplakia in nonneoplastic diseases
The main histological feature of LL is represented by the epithelial thickening (hyperplasia) with preserved epithelial maturation or cellular atypia. Conversely, the presence of abnormal epithelial maturation and cellular atypia should raise suspicion for dysplasia. Despite the clinical setting of LL, dysplasia should be always suspected and ruled out through a proper histological assessment of mucosal specimens. In this regard, biopsy interpretation represents a critical part of the patient’s management.
3.1 Phonotrauma
LL represents the main clinical presentation of laryngeal dysplasia and carcinoma. Nonetheless, it can also be detected in inflammatory disease of the upper airways. The so-called
3.2 Chronic laryngitis
Laryngeal inflammation for at least 3-weeks-long is usually referred to as
3.3 Laryngeal involvement in systemic non neoplastic diseases
Larynx can be rarely involved in systemic diseases, such as autoimmune diseases that could mimic chronic laryngitis. Laryngeal lichen planus (LP) is a rare - and probably under-recognized - autoimmune disease affecting both skin and mucosal membranes. Although mucosal LP is more frequent in the oral cavity, where it should be distinguished from pemphigoid of the mucosal membranes, laryngeal involvement has been reported as well. As in chronic laryngitis, laryngeal LP harbors sub-epithelial inflammation, squamous hyperplasia, and superficial ortho- and para-keratosis without dysplasia but, in contrast, laryngeal LP usually presents at least focally, with a sub-epithelial “band-like” inflammation, cytoplasmic vacuolization in basal keratinocytes and basal apoptotic (
4. Laryngeal leukoplakia and dysplasia
Laryngeal dysplasia (LD) is defined by a spectrum of both maturation abnormalities and nuclear atypia involving the laryngeal epithelial lining, that may or may not precede an invasive squamous carcinoma. Even though dysplasia includes atypical cellular features, such a term should not be considered synonymous with atypia, as the latter indicates atypical nuclear features alone, excluding the maturation abnormalities. Thus, the two terms should not be used interchangeably. Dysplastic changes encompass crowded immature epithelial cells, loss of cellular polarity, nuclear pleomorphism and hyperchromasia, increased nucleus-to-cytoplasm ratio, and mitoses including atypical forms. Such cellular and architectural abnormalities can be found as either superimposed into pre-existing squamous hyperplasia or raised into non-hyperplastic laryngeal epithelium. Hence squamous hyperplasia should not be considered a prerequisite for developing LD. According to the dysplasia model applied for the uterine cervix, LD is defined as mild, moderate, and severe regarding the level of epithelial involvement. In situ carcinoma (CIS-non-keratinizing type) is defined by the full-thickness mucosal epithelial dysplastic change without infiltration of the basement membrane. Conversely to the uterine cervix, the larynx usually harbors keratinizing dysplasia, which exhibits by definition at least focal squamous maturation, making the concept of a full-thickness dysplastic involvement not suitable for laryngeal CIS. As a consequence, the use of the term
4.1 Grading systems
LD represents the earliest lesion manifesting, at both microscopic and molecular levels, neoplastic features [5]. Although the progression risk differs according to the grading, LD is widely considered the precursor lesion of squamous cell carcinoma (SCC). The LD grading has been a matter of disagreement among clinicians and pathologists, because of terminology was not uniform, grade designation seemed burdened by subjectivity and the risk stratification was often imprecise. The role of grading is mainly focused on the definition of the progression risk toward SCC. Squamous hyperplasia carries a very low risk of developing invasive SCC, whereas the presence of dysplasia increased such a risk [21]. In order to improve uniformity in diagnostic terminology, several grading systems and classification schemes have been proposed. It was previously suggested that
Abnormal maturation | WHO 2005 | SIN classification | Ljubljana classification (amended version) | LIN classification | WHO 2017 |
---|---|---|---|---|---|
Basal third | Mild dysplasia | SIN 1 | Low Grade SIL | LIN 1 | Low Grade Dysplasia |
Lower half | Moderate dysplasia | SIN 1 or SIN 2 | LIN 2 | ||
More than half | SIN 2 | High Grade SIL | LIN 3 | High Grade Dysplasia | |
Upper third | Severe dysplasia | ||||
Full thickness | CIS | CIS |
4.2 Carcinogenic mechanisms
Several causative agents and carcinogenic mechanisms have been suggested in SCC. The concept of
The carcinogenic role of the
5. Laryngeal leukoplakia and squamous cell cancer
Any neoplastic infiltration beyond the basement membrane into the underlying connective tissue should be referred to as invasive SCC.
The
The
5.1 Histological variants of laryngeal SCC
5.1.1 Papillary SCC
It affects men more than women. The larynx is the most common location, even though it can be seen in the oral cavity and hypopharynx. Papillary SCC usually occurs de novo since the occurrence of cancer at the site of previous papilloma has been rarely reported. The role of HPV infection has been established by in situ hybridization study in such cancer variants [56]. The tumor presented as an exophytic mass, histologically characterized by finger-like projections supported by fibrovascular cores or by a broad-based cauliflower-like growth pattern. Surface keratinization is usually scanty or absent, differentiating the papillary from the verrucous subtype of SCC. Cytologic malignant features are evident in the neoplastic epithelium of the papillary SCC, again differentiating it from verrucous SCC.
5.1.2 Verrucous SCC
It is a highly differentiated variant of SCC affecting men more than women, mostly in the laryngeal glottis. Tumor growth is locally destructive, without metastatic potential. Tobacco smoking and viral induction have been suggested as etiologic factors. The tumor presented as an exophytic mass, histologically characterized by a benign-appearing proliferation composed of uniform squamous cells without significant atypia nor mitoses, prominent surface
5.1.3 Spindle cells SCC
It is a highly aggressive biphasic tumor composed of both SCC (CIS or invasive) and spindle cells malignant neoplasm, affecting men more than women. In the larynx, both the glottis and the supra-glottic region can be involved. Previous irradiation has been involved as a risk factor, whilst there was no significant correlation with tobacco smoking, alcohol consumption, and occupational/environmental factors [58, 59]. Spindle cells SCC are not related to HPV infection [60]. Tumor mass usually presents as exophytic neoplasm consisting in a malignant undifferentiated spindle cells proliferation with SCC nests. The spindle cells’ component usually predominates, and it is characterized by prominent cytological atypia and frequent mitoses, often associated with necrotic foci. The growth pattern can vary from fascicular to storiform and palisading. Areas of stromal collagenization and myxomatous degeneration can be seen. Heterologous elements could be detected, mostly consisting of chondro- and osteo-sarcomatous foci. Epithelial derivation is supported by the intimate relationship with conventional SCC and by epithelial markers’ expression. Spindle cells were found to express cytokeratins in the majority of cases, even though vimentin expression and myogenic differentiation have been reported [18, 60, 61]. Overall, spindle cells SCC usually behave malignantly, even though flat and ulcerating lesions have a worse prognosis if compared to exophytic variants [62]. Reactive myo-fibroblastic proliferations, mucosal malignant melanomas, and sarcomas should be considered in the differential [63, 64, 65].
5.1.4 Basaloid SCC
It is a high-grade variant of SCC involving palatal tonsils, tongue, hypopharynx, and larynx, the latter being mostly affected in the supraglottic region. Known etiologic factors are tobacco smoking and alcohol consumption. Tumor grossly presents as a firm whitish mass, associated with central necrosis. Basaloid cells, characterized by atypical hyperchromatic nuclei and scanty cytoplasm, increased mitotic activity, and peripheral nuclear palisading, are intermingled with conventional SCC. Muco-hyaline stromal deposition can be seen. Basaloid cells usually expressed epithelial markers, even though Vimentin could be expressed in a subset. Adenoid cystic and neuroendocrine carcinoma should be considered in the differential [66, 67].
5.1.5 Undifferentiated (lymphoepithelioma-like/nasopharygeal type) SCC
Undifferentiated (lymphoepithelioma-like/nasopharygeal type) SCC can rarely affect larynx and hypopharynx. Such tumors resulted more prevalent in the Chinese population and related to EBV infection. At histology, keratinizing and nonkeratinizing forms have been described, being the latter further subdivided into differentiated and undifferentiated types [68].
5.2 Molecular prognostic markers
The risk of progression is known to vary in dysplastic LL according to the grading of dysplasia [69, 70]. The use of biomarkers to highlight the cumulative effect of genetic mutations can aid in a more accurate establishment of progression in LL. Prognostic biomarkers can be subdivided into four categories: (1) proliferation; (2) cell cycle control; (3) cell adhesion and invasion; (4) immune checkpoints. Malignant cells are known to acquire a high proliferative rate, that can be monitored by using several markers. Ki67 is a nuclear protein widely studied as proliferative marker, even though it does not represent a reliable marker of malignant transformation in laryngeal dysplasia [71, 72, 73, 74]. TP53 is a well-established tumor suppressor gene involved in head and neck SCC. The loss of wild-type p53 activity, as well as p16 and cyclin D1, were frequently detected in many cancer types and were found to be involved in tumor progression [75, 76]. A specific isoform of CD44 (CD44v6) was established to interact with Osteopontin, which is known to be elevated in many cancer types and correlates with laryngeal SCC progression in the larynx [73]. Beta-catenin protein is coded by CTNNB1 gene and is involved together with E-cadherin in intercellular adherence and epithelial structure maintenance. Alteration in beta-catenin protein expression plays a role in cancer progression and invasiveness [77]. In the past few years, tumor inflammatory microenvironment has gained more attention. In that setting, both tumors devoid of immune infiltrates and others marked by abundant T cell infiltrates have been detected. Programmed cell death protein 1 (PD1/CD279) is a member of the CD28 family of T cell co-stimulatory proteins that includes CTLA-4, ICOS, and BTLA. It has two specific ligands PD-L1 (B1-H1/CD274) and PD-L2 (B7-H2/CD273) which down-regulate T cell activation on binding to PD1. The PD-1/PD-L1 interaction represents a critical immune checkpoint in the adaptive immune resistance of SCC. Immunohistochemical assays have been employed to evaluate the expression of immune checkpoints in the tumor microenvironment, but limitations have been outlined by many authors, including the use of different antibody clones (including 5H1, E1L3N, SP142, 28–8, 22C3, SP142, and SP263) and the lack of a standardized scoring system. [78, 79, 80].
6. Conclusions
The clinical management of LL is a daily critical challenge for Otolaryngologists, who must be aware of the broad spectrum of pathological conditions that could underlie leukoplakia. An effective clinical-pathological correlation represents the basis for proper treatment planning in such patients.
Acknowledgments
Funding information: GRANT: Fondazione IRCCS Istituto Nazionale dei Tumori.
References
- 1.
Wenig BM. Atlas of Head and Neck Pathology. Phyladelphia, PA: Saunders; - 2.
Park JC, Altman KW, Prasad VMN, Broadhurst M, Akst LM. Laryngeal leukoplakia: State of the art review. Otolaryngology and Head and Neck Surgery. 2021; 164 (6):1153-1159 - 3.
Lippert D, Hoffman MR, Dang P, McCulloch TM, Hartig GK, Dailey SH. In-office biopsy of upper airway lesions: Safety, tolerance, and effect on time to treatment. The Laryngoscope. 2015; 125 (4):919-923 - 4.
Standring S. Gray's Anatomy. 41st ed. Edinburgh: Elsevier Churchill Livingstone; 2016 - 5.
Ferlito A, Devaney KO, Woolgar JA, Slootweg PJ, Paleri V, Takes RP, et al. Squamous epithelial changes of the larynx: Diagnosis and therapy. Head & Neck. 2012; 34 (12):1810-1816. DOI: 10.1002/hed.21862 Epub 2011 Oct 3 - 6.
Rousseau B, Kojima T, Novaleski CK, et al. Recovery of vocal fold epithelium after acute Phonotrauma. Cells, Tissues, Organs. 2017; 204 (2):93-104 - 7.
Titze IR. Mechanical stress in phonation. Journal of Voice. 1994; 8 :99-105 - 8.
Rousseau B, Suehiro A, Echemendia N, Sivasankar M. Raised intensity phonation compromises vocal fold epithelial barrier integrity. The Laryngoscope. 2011; 121 :346-351 - 9.
Kojima T, Van Deusen M, Jerome WG, Garrett CG, Sivasankar MP, Novaleski CK, et al. Quantification of acute vocal fold epithelial surface damage with increasing time and magnitude doses of vibration exposure. PLoS One. 2014; 9 :e91615 - 10.
Naunheim MR, Carroll TL. Benign vocal fold lesions: Update on nomenclature, cause, diagnosis, and treatment. Current Opinion in Otolaryngology & Head and Neck Surgery. 2017; 25 (6):453-458 - 11.
Joniau S et al. Reflux and laryngitis: A systematic review. Otolaryngology – Head and Neck Surgery. 2007; 136 (5):686-692 - 12.
Reulbach TR et al. Occult laryngeal pathology in a community-based cohort. Otolaryngology – Head and Neck Surgery. 2001; 124 (4):448-450 - 13.
Rutt et al. Clinicopathologic aspects of vocal fold leucoplakia in smokers and nonsmokers. Journal of Voice. 2021; 35 (5):779-784 - 14.
Leoncini G, Marin MG, Squeglia C, Aquilini SE, Zanetti L. Laryngeal lichen planus mimicking vocal fold dysplasia. Auris, Nasus, Larynx. 2021; S0385-8146 (21):00125-00125 - 15.
Harris G, Lachmann H, Hawkins P, Sandhu G. One hundred cases of localized laryngeal amyloidosis - evidence for future management. The Laryngoscope. 2021; 131 (6):E1912-E1917 - 16.
Westermark P. Localized AL amyloidosis: A suicidal neoplasm? Upsala Journal of Medical Sciences. 2012; 117 :244-250 - 17.
Gale N, Blagus R, El-Mofty SK, et al. Evaluation of a new grading system for laryngeal squamous intraepithelial lesions - a proposed unified classification. Histopathology. 2014; 65 (4):456-464 - 18.
Wenig BM. Squamous cell carcinoma of the upper aerodigestive tract: Precursors and problematic variants. Modern Pathology. 2002; 15 (3):229-254 - 19.
Crissman JD, Gnepp DR, Goodman ML, Hellquist H, Johns ME. Preinvasive lesions of the upper aerodigestive tract: Histologic definitions and clinical implications (a symposium). Pathology Annual. 1987; 22 (Pt. 1):311-352 - 20.
Blackwell KE, Fu YS, Calcaterra TC. Laryngeal dysplasia. A clinicopathologic study. Cancer. 1995; 75 :457-463 - 21.
Gale N, Kambic V, Michaels L, Cardesa A, Hellquist H, Zidar N, et al. The Ljubljana classification: A practical strategy for the diagnosis of laryngeal precancerous lesions. Advances in Anatomic Pathology. 2000; 7 (4):240-251 - 22.
Crissman JD, Zarbo RJ. Quantitation of DNA ploidy in squamous intraepithelial neoplasia of the laryngeal glottis. Archives of Otolaryngology – Head & Neck Surgery. 1991; 117 (2):182-188 - 23.
Crissman JD, Zarbo RJ, Drozdowicz S, Jacobs J, Ahmad K, Weaver A. Carcinoma in situ and microinvasive squamous carcinoma of the laryngeal glottis. Archives of Otolaryngology – Head & Neck Surgery. 1988; 114 (3):299-307 - 24.
Hellquist H, Cardesa A, Gale N, Kambic V, Michaels L. Criteria for grading in the Ljubljana classification of epithelial hyperplastic laryngeal lesions. A study by members of the working group on epithelial hyperplastic laryngeal lesions of the European Society of Pathology. Histopathology. 1999; 34 (3):226-233 - 25.
Gale N, Poljak M, Zidar N. Update from the 4th edition of the World Health Organization classification of head and neck Tumours: What is new in the 2017 WHO blue book for Tumours of the hypopharynx, larynx, trachea and Parapharyngeal space. Head and Neck Pathology. 2017; 11 (1):23-32 - 26.
Gale N, Hille J, Jordan RC, Nadal A, Williams MD. Regarding laryngeal precursor lesions: Interrater and intrarater reliability of histopathological assessment. The Laryngoscope. 2019; 129 (3):E91-E92 - 27.
Slaughter DP, Southwick HW, Smejkal W. “Field cancerization” in oral stratified squamous epithelium. Clinical Implications of Multicentric Origin. Cancer. 1953; 6 (5):963-968 - 28.
Willenbrink TJ, Ruiz ES, Cornejo CM, et al. Field cancerization: Definition, epidemiology, risk factors, and outcomes. Journal of the American Academy of Dermatology. 2020; 83 (3):709-717 - 29.
Licciardello JTW, Spitz MR, Hong WK. Multiple primary cancer in patients with cancer of the head and neck: Second cancer of the head and neck, esophagus and lung. International Journal of Radiation Oncology, Biology, Physics. 1989; 17 :467-476 - 30.
Cohn AM, Peppard SB. Multiple primary malignant tumors of the head and neck. American Journal of Otolaryngology. 1980; 1 :411-417 - 31.
Carey TE. Field cancerization: Are multiple primary cancers monoclonal or polyclonal? Annals of Medicine. 1996; 28 :183-188 - 32.
Worsham MJ, Wolman SR, Carey TE, Zarbo RJ, Benninger MS, Van Dyke DL. Common clonal origin of synchronous primary head and neck squamous cell carcinomas: Analysis by tumor karyotypes and fluoresence in situ hybridization. Human Pathology. 1995; 26 :251-261 - 33.
Bedi GC, Westra WH, Gabrielson E, et al. Multiple head and neck tumors: Evidence for common clonal origin. Cancer Research. 1995; 26 :251-261 - 34.
Califano J, van der Riet P, Westra W, et al. Genetic progression model for head and neck cancer: Implications for field cancerization. Cancer Research. 1996; 56 :2484-2487 - 35.
Vokes EE, Weichselbaum RR, Lippman SM, Hong WK. Head and neck cancer. The New England Journal of Medicine. 1993; 328 :184-194 - 36.
Argiris A, Karamouzis MV, Raben D, Ferris RL. Head and neck cancer. Lancet. 2008; 371 :1695-1709 - 37.
Braakhuis BJ, Tabor MP, Kummer JA, et al. A genetic explanation of Slaughter's concept of field cancerization: Evidence and clinical implications. Cancer Research. 2003; 63 (8):1727-1730 - 38.
Schantz SP, Yu G. Epidemiology. In: Fu YS, Wenig BM, Abeymayor E, Wenig BL, editors. Head and Neck Pathology with Clinical Correlations. Philadelphia: Churchill Livingstone; 2000. pp. 38-61 - 39.
Fouret P, Martin F, Flahault A, Saint-Guily JL. Human papillomavirus infection in the malignant and premalignant head and neck epithelium. Diagnostic Molecular Pathology. 1995; 4 :122-127 - 40.
Duray A, Descamps G, Arafa M, et al. High incidence of high-risk HPV in benign and malignant lesions of the larynx. International Journal of Oncology. 2011; 39 (1):51-59 - 41.
Gillison ML, Koch WM, Capone RB, et al. Evidence for a causal association between human papillomavirus and a subset of head and neck cancers. Journal of the National Cancer Institute. 2000; 92 :709-720 - 42.
Chernock RD, Wang X, Gao G, Lewis JS Jr, Zhang Q , Thorstad WL, et al. Detection and significance of human papillomavirus, CDKN2A(p16) and CDKN1A(p21) expression in squamous cell carcinoma of the larynx. Modern Pathology. 2013; 26 (2):223-231 - 43.
Hobbs CG, Birchall MA. Human papillomavirus infection in the etiology of laryngeal carcinoma. Current Opinion in Otolaryngology & Head and Neck Surgery. 2004; 12 (2):88-92 - 44.
del Pino M, Bleeker MC, Quint WG, Snijders PJ, Meijer CJ, Steenbergen RD. Comprehensive analysis of human papillomavirus prevalence and the potential role of low-risk types in verrucous carcinoma. Modern Pathology. 2012; 25 (10):1354-1363 - 45.
Jo VY, Mills SE, Stoler MH, Stelow EB. Papillary squamous cell carcinoma of the head and neck: Frequent association with human papillomavirus infection and invasive carcinoma. The American Journal of Surgical Pathology. 2009; 33 (11):1720-1724 - 46.
Echanique KA, Desai SV, Marchiano E, et al. Laryngeal verrucous carcinoma: A systematic review. Otolaryngology and Head and Neck Surgery. 2017; 156 :38-45 - 47.
Odar K, Kocjan BJ, Hošnjak L, Gale N, Poljak M, Zidar N. Verrucous carcinoma of the head and neck—Not a human papillomavirus-related tumor? Journal of Cellular and Molecular Medicine. 2014; 18 :635-645 - 48.
Russell JO, Hoschar AP, Scharpf J. Papillary squamous cell carcinoma of the head and neck: A clinicopathologic series. American Journal of Otolaryngology. 2011; 32 :557-563 - 49.
El-Mofty SK, Patil S. Human papillomavirus (HPV)-related oropharyngeal nonkeratinizing squamous cell carcinoma: Characterization of a distinct phenotype. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics. 2006; 101 :339-345 - 50.
Gorgoulis VG, Zacharatos P, Kotsinas A, Kyroudi A, Rassidakis AN, Ikonomopoulos JA, et al. Human papilloma virus (HPV) is possibly involved in laryngeal but not in lung carcinogenesis. Human Pathology. 1999; 30 (3):274-283 - 51.
Crissman JD, Zarbo RJ. Dysplasia, in situ carcinoma and progression to invasive squamous cell carcinoma of the upper aerodigestive tract. The American Journal of Surgical Pathology. 1989; 13 (suppl. 1):5-16 - 52.
Gillis TM, Incze MS, Vaughan CW, Simpson GT. Natural history and management of keratosis, atypia, carcinoma in situ and microinvasive cancer of the larynx. American Journal of Surgery. 1983; 146 :512-516 - 53.
Barnes L. Diseases of the larynx, hypopharynx and esophagus. In: Barnes L, editor. Surgical Pathology of the Head and Carcinoma in situ. Vol. 2. Clinical Otolaryngology; 1977. p. 292 - 54.
Ferlito A, Carbone A, De Santo LW, et al. Early cancer of the larynx: The concept as defined by clinicians, pathologists and biologists. The Annals of Otology, Rhinology, and Laryngology. 1996; 105 :245-250 - 55.
Suarez PA, Adler-Storthz K, Ma L, et al. Papillary squamous cell carcinoma of the upper aerodigestive tract: a clinicopathological and molecular study. Head Neck. 2000; 22 :360-368 - 56.
Medina JE, Dichtel W, Luna MA. Verrucous squamous carcinomas of the oral cavity. A clinicopathological study of 104 cases. Archives of Otolaryngology. 1984; 110 :437-440 - 57.
Hellquist H, Olofsson J. Spindle cell carcinoma of the larynx. APMIS. 1989; 97 (12):1103-1113 - 58.
Zarbo RJ, Crissman JD, Venkat H, Weiss MA. Spindle-cell carcinoma of the upper aerodigestive tract mucosa. An immunohistologic and ultrastructural study of 18 biphasic tumors and comparison with seven monophasic spindle-cell tumors. The American Journal of Surgical Pathology. 1986; 10 (11):741-753 - 59.
Watson RF, Chernock RD, Wang X, Liu W, Ma XJ, Luo Y, et al. Spindle cell carcinomas of the head and neck rarely harbor transcriptionally-active human papillomavirus. Head and Neck Pathology. 2013; 7 (3):250-257 - 60.
Lewis JE, Olsen KD, Sebo TJ. Spindle cell carcinoma of the larynx: Review of 26 cases including DNA content and immunohistochemistry. Human Pathology. 1997; 28 (6):664-673 - 61.
Berthelet E, Shenouda G, Black MJ, Picariello M, Rochon L. Sarcomatoid carcinoma of the head and neck. American Journal of Surgery. 1994; 168 (5):455-458 - 62.
Tay SY, Balakrishnan A. Laryngeal inflammatory myofibroblastic tumor (IMT): A case report and review of the literature. Journal of Medical Case Reports. 2016; 10 (1):180 - 63.
Wenig BM. Laryngeal mucosal malignant melanoma. A clinicopathologic, immunohistochemical, and ultrastructural study of four patients and a review of the literature. Cancer. 1995; 75 (7):1568-1577 - 64.
Mandell DL, Brandwein MS, Woo P, Som PM, Biller HF, Urken ML. Upper aerodigestive tract liposarcoma: Report on four cases and literature review. The Laryngoscope. 1999; 109 (8):1245-1252 - 65.
Banks ER, Frierson HF Jr, Mills SE, George E, Zarbo RJ, Swanson PE. Basaloid squamous cell carcinoma of the head and neck. A clinicopathologic and immunohistochemical study of 40 cases. The American Journal of Surgical Pathology. 1992; 16 (10):939-946 - 66.
Morice WG, Ferreiro JA. Distinction of basaloid squamous cell carcinoma from adenoid cystic and small cell undifferentiated carcinoma by immunohistochemistry. Human Pathology. 1998; 29 (6):609-612 - 67.
Ferlito A, Weiss LM, Rinaldo A, Carbone A, Devaney KO, MacMillan C, et al. Lymphoepithelial carcinoma of the larynx hypopharynx, and trachea. The Annals of Otology, Rhinology, and Laryngology. 1997; 106 (5):437-444 - 68.
Jabarin B, Pitaro J, Marom T,Muallem-Kalmovich L. Dysplastic changes in patients with recurrent laryngeal leukoplakia: Importance of long-term follow-up. The Israel Medical Association Journal. 2018; 20 (10):623-626 - 69.
Weller MD, Nankivell PC, McConkey C, Paleri V, Mehanna HM. The risk and interval to malignancy of patients with laryngeal dysplasia; a systematic review of case series and meta-analysis. Clinical Otolaryngology. 2010; 35 (5):364-372 - 70.
Wan P, Ongkasuwan J, Martinez J, Sandulache V, Deng D, Jiang J, et al. Biomarkers for malignant potential in vocal fold leukoplakia: A state of the art review. Otolaryngology and Head and Neck Surgery. 2021; 164 (4):751-758 - 71.
Vukelic J, Dobrila-Dintinjana R, Dekanic A, Marijic B, Cubranic A, Braut T. The relevance of assessing the cell proliferation factor Ki-67 in squamous cell carcinoma of the larynx. BioMed Research International. 2019; 2019 :8142572 - 72.
Mirza S, Jeannon JP, Soames J, Wilson JA. Is Ki67 a marker for the transformation of laryngeal dysplasia to carcinoma? Acta Oto-Laryngologica. 2006; 126 (4):418-421 - 73.
López F, Alvarez-Marcos C, Alonso-Guervós M, Domínguez F, Suárez C, Hermsen MA, et al. From laryngeal epithelial precursor lesions to squamous carcinoma of the larynx: The role of cell cycle proteins and β-catenin. European Archives of Oto-Rhino-Laryngology. 2013; 270 (12):3153-3162 - 74.
Muller PA, Vousden KH. Mutant p53 in cancer: New functions and therapeutic opportunities. Cancer Cell. 2014; 25 (3):304-317 - 75.
Papadimitrakopoulou V, Izzo JG, Liu DD, Myers J, Ceron TL, Lewin J, et al. Cyclin D1 and cancer development in laryngeal Premalignancy patients. Cancer Prevention Research (Philadelphia, Pa.). 2009; 2 (1):14-21 - 76.
Staibano S, Merolla F, Testa D, Iovine R, Mascolo M, Guarino V, et al. OPN/CD44v6 overexpression in laryngeal dysplasia and correlation with clinical outcome. British Journal of Cancer. 2007; 97 (11):1545-1551 - 77.
Lyford-Pike S, Peng S, Young GD, Taube JM, Westra WH, Akpeng B, et al. Evidence for a role of the PD-1:PD-L1 pathway in immune resistance of HPV-associated head and neck squamous cell carcinoma. Cancer Research. 2013; 73 (6):1733-1741 - 78.
Strome SE, Dong H, Tamura H, Voss SG, Flies DB, Tamada K, et al. B7-H1 blockade augments adoptive T-cell immunotherapy for squamous cell carcinoma. Cancer Research. 2003; 63 (19):6501-6505 - 79.
Cho YA, Yoon HJ, Lee JI, Hong SP, Hong SD. Relationship between the expressions of PD-L1 and tumor-infiltrating lymphocytes in oral squamous cell carcinoma. Oral Oncology. 2011; 47 (12):1148-1153 - 80.
Oliveira-Costa J, Fiorini de CA, Gobbi da SG, Amaya P, Wu Y, Jenny Park K, et al. Gene expression patterns through oral squamous cell carcinoma development: PD-L1 expression in primary tumor and circulating tumor cells. Oncotarget. 2015; 6 :20902-20920