Diagnostic Complexities of Oral Squamous Cell Carcinoma

Squamous cell carcinoma, which originates from oral epithelial tissue, accounts for about 90% of oral cancer globally.¹ Oral squamous cell carcinoma (OSCC) and oropharyngeal squamous cell carcinoma (OPSCC), though both squamous cell carcinoma, are now accepted as distinct clinical entities with unique pathophysiology and clinical characteristics.² For example, environmental carcinogens in tobacco smoking and betel nut chewing are strongly associated with OSCC, while human papilloma virus (HPV) accounts for approximately 71% and 52% of OPSCCs in the United States and United Kingdom, respectively. HPV-16, in particular, is implicated in 85% to 96% of HPV-associated OPSCC.³ Recent data from the Surveillance, Epidemiology, and End Results (SEER) program reports 68.5% 5-year survival rate in OSCC/OPSCC, with the staging of cancer exerting a strong influence on length of survival.⁴

Treatment for OSCC and OPSCC is primarily driven by cancer stage and may include surgery alone or in combination with adjuvant or neoadjuvant radiation, chemotherapy, and/or targeted therapy with the monoclonal antibody cetuximab.⁵ Oral cancers diagnosed at later stages are associated with increased morbidity and mortality, stressing the importance of prompt diagnosis. This article highlights critical elements in lesion assessment in a patient with a complex oral lesion history who was ultimately diagnosed with OSCC through the University of Washington School of Dentistry Oral Medicine Clinical Services (UWOMCS).

A 66-year-old Asian man was referred to UWOMCS by his general dentist for assessment of an exophytic lesion on the left lateral tongue of 5-year duration. The patient described tenderness to touch on the left side of the tongue, sensitivity to hot and spicy foods, and 5 out of 10 level pain with eating. His history was significant for four previous biopsies (discussed below) prior to presentation at UWOMCS, with lesion recurrence after each procedure. Teeth adjacent to the site had been smoothed and a nightguard fabricated to rule out trauma as a contributing factor. Risk factors for oral cancer were limited to a 3.5 pack-year smoking history, discontinued 14 years prior to his initial appointment at UWOMCS. The patient's medical history was significant for atrial fibrillation and arthritis managed with atenolol and aspirin, respectively.

The first incisional biopsy completed in 2018 identified hyper-parakeratosis with eosinophilic plasma pooling suggestive of frictional etiology, such as chronic tongue chewing/biting. A second incisional biopsy completed 2 years later (2020) was also consistent with tongue chewing. There was no evidence of epithelial dysplasia or carcinoma in the second sample, although it was noted that there was minimal intact epithelium in the sample. The third biopsy, completed in 2021, included three tissue fragments measuring 1 cm x 0.3 cm x 0.2 cm in aggregate, and identified severe epithelial dysplasia but no definitive invasion into the underlying connective tissue. The pathologist recommended surgical excision of the remaining lesion to rule out invasion beyond the basement membrane. A fourth incisional biopsy, submitted in 2022, included two tissue fragments measuring 0.7 cm x 0.4 cm x 0.2 cm in aggregate and found hyperkeratosis and acanthosis with no evidence of epithelial dysplasia.

On initial presentation in UWOMCS, examination identified a firm, raised, circular mass with irregular surface texture measuring 9 mm x 10 mm x 2 mm. The lesion was a mixed red and white color intermixed with areas of yellow (Figure 1). Two partially connected areas of leukoplakia were located just anterior to the primary lesion. VELscope^® (LED Dental, Inc., velscope.com) examination revealed loss of fluorescence along the middle and mesial portions of the primary lesion. Toluidine blue staining demonstrated uptake along the superior border and scattered within the body of the lesion (Figure 2). Immediate biopsy was completed within the anterior portion of the primary lesion, which featured the mixed red and white coloration and site of greatest dye uptake.

Histopathology confirmed moderate-to-well-differentiated OSCC. Biopsy results were reviewed with the patient and a referral was coordinated to University of Washington Otolaryngology-Head and Neck Surgery. Staging was confirmed to be T1N0M0 after computed tomography (CT) (with contrast) identified no enlargement in the cervical lymph nodes. Although there was no definitive invasion, lesion thickness prompted neck dissection due to potential for occult cervical metastasis. The patient underwent left partial glossectomy with clean margins and selective neck dissection with removal of eight lymph nodes and the left submandibular salivary gland (all of which were negative for carcinoma). Post-surgical follow-up appointments confirmed that the patient was healing as expected with complete preservation of oral function. Regular clinical follow-up, with repeat examinations, was recommended for 5 years after the surgery. Surveillance was planned, and he will be followed regularly over the next 5 years.

Red and white plaque-like lesions (erythroplakia, leukoplakia, and mixed erythroleukoplakia), non-healing ulcerations, and exophytic, indurated masses raise concern for OSCC, particularly when occurring at high-risk sites.⁶ The ventrolateral surface of the tongue is the most common location for oral cancer with more than 50% of OSCCs occurring at this site.⁷ The next most common locations include the floor of the mouth, lower alveolar ridge, and buccal mucosa.¹

While exophytic lesions, like the one in this case, raise concern for OSCC, the differential diagnosis also includes traumatic and infectious conditions. Traumatic ulcerative granuloma with stromal eosinophilia (TUGSE) is a relatively rare condition that may present as an exophytic mass or ulceration with indurated margins, most often on the lateral surfaces of the tongue.⁸ In TUGSE, deep trauma to tissue triggers abnormal wound healing characterized by dense infiltration of eosinophils that perpetuate the lesion. Interestingly, lesions often heal following biopsy.⁷ In the present case, a traumatic etiology was initially considered by the patient's dentist due to its location, clinical appearance, and eosinophilic plasma pooling on initial biopsy.

Persistent ulcers and irregular masses also raise suspicion for deep bacterial and/or fungal infection. Syphilis is an infectious disease, mediated by the bacterium Treponema pallidum, which is transmitted sexually or present congenitally.⁹ The primary stage of syphilis involves the development of a chancre, which can present clinically as an ulcer.⁹ Importantly, primary chancre will often resolve within 3 to 8 weeks with or without intervention, which can lead to delayed diagnosis of the underlying disease.⁹ Tuberculosis, a respiratory infection caused by Mycobacterium tuberculosis, may present as a non-painful, indurated oral ulcer.¹⁰ Although rare in the United States, tuberculosis should be considered in patients with cough persisting for more than 2 weeks, particularly when accompanied by bloody sputum and unexplained weight loss.¹¹ In addition, data from the Centers for Disease Control and Prevention shows that tuberculosis cases are rising in the United States, specifically in certain racial/ethnic groups, children under 4 years old, and people who are incarcerated.¹² Fungal infections, including histoplasmosis and blastomycosis, may also be considered on the differential diagnosis of isolated oral ulceration, but occur almost exclusively in the setting of immunosuppression.¹³ Although extrapulmonary involvement is rare, oral manifestations include deep ulcers on the tongue, palate, gingiva, and buccal mucosa.¹³

This case highlights several complexities that may arise in the diagnosis of OSCC. The presence of a chronic, recurring lesion presents a challenge for accurate surveillance and diagnosis, particularly when the lesion persists for many years. It can be difficult to know when to intervene and when to recommend repeat biopsy when previous biopsies have been negative for dysplasia and carcinoma. Accurate diagnosis cannot occur without biopsy and is dependent on a representative, high-quality tissue sample to avoid a false-negative or inconclusive result.

Several elements in this patient's case factored into the decision to pursue additional diagnostic testing despite his history of repeat biopsies. Reports of the lesion's initial presentation were consistent with leukoplakia at a high-risk site. Leukoplakic lesions, while not inherently dysplastic, have the potential to transform to squamous cell carcinoma with an annual transformation rate of 2% to 3%.¹⁴ Lesions are of greatest concern in individuals with history of smoking or in situations where no etiologic factor can be identified, ie, idiopathic leukoplakia.¹⁵ In this case, the patient's past smoking history and the persistence of the lesion for more than 2 weeks after removing potential causes of friction raised concern for OSCC. Lesion recurrence following initial biopsy and the change in color to a mixed red and white appearance were also highly concerning. Red plaques, ie, erythroplakia, have an even higher risk for malignancy, with most erythroplakias demonstrating carcinoma in situ, severe epithelial dysplasia, or carcinoma.^16,17 Additional characteristics raising suspicion for dysplasia and/or carcinoma include ulceration, induration, high-risk locations like the lateral tongue and floor of mouth, lesion duration, and non-responsiveness to treatment (all of which were present in this case over time).¹⁷

Once a lesion has been identified as potentially dysplastic, a decision must be made regarding surveillance and potential next steps. Trauma should be ruled out by removing potential sources of irritation and allowing no more than 2 weeks for healing before clinical reassessment. Red and white lesions may represent lesions caused by infectious or immune-related etiologies. Additional diagnostics (eg, biopsy, culture) are often indicated to establish a definitive diagnosis, although therapeutic medication trials may also be valuable in situations where close follow-up is possible, particularly when an infectious or immune-mediated etiology is suspected.

Adjunctive diagnostic testing, specifically toluidine blue vital dye staining and autofluorescence visualization, played an important role in this case by helping to determine the optimal site for biopsy.¹⁷ Toluidine blue has an increased affinity to areas of high mitotic activity and inflammation, which may be present in dysplasia and carcinoma.¹⁷ Autofluorescence imaging utilizes blue light to illuminate tissues; normal tissues will fluoresce, while tissue with increased mitotic activity, inflammation, or angiogenesis will exhibit loss of fluorescence.¹⁸ False positives are possible with these methods, and they therefore should be used with caution, especially when used in screening. However, they remain valuable adjuncts, particularly when used in combination to assess suspicious lesions and select biopsy sites.¹⁹

Proper biopsy techniques are critical to avoid misdiagnosis. The sample should be intact and taken from tissues that look the most abnormal or are adjacent to any ulcers.²⁰ The raised border surrounding the ulcer is optimal for sampling rather than the center of the ulcer.²⁰ In a mixed red-white lesion, selecting a dense, white area should be avoided. These areas are often highly keratinized and less likely to demonstrate the characteristic features of dysplasia and carcinoma, potentially leading to an inaccurate diagnosis of non-specific keratosis. Selecting a thinner red area is less likely to result in a false-negative result. The surgeon can also ensure a more representative sample by collecting a larger tissue sample or multiple smaller samples from different areas of the lesion. The biopsy should capture sufficient depth to evaluate the depth of invasion if OSCC is suspected.²¹ When OSCC is suspected, biopsy must include both the basement membrane and the underlying connective tissue.²¹ Biopsy depths of at least 2 mm to 5 mm or three times the depth of the lesion have all been described in the literature regarding depth criteria. In this case, prior aggregate tissue samples were insufficient to comment on potential depth of invasion.

Once a biopsy has been completed, proper interpretation of the report is critical. A biopsy report may identify a non-malignant ("benign") process, such as frictional hyperkeratosis, premalignant tissue changes, such as epithelial dysplasia, or malignancy, such as OSCC. In the case of epithelial dysplasia, lesions are classified as low-grade or high-grade based on their risk for malignant transformation. Low-grade dysplasias are often managed with routine monitoring, while "high-risk dysplasia" (previously "moderate" and "severe" dysplasia) should be surgically removed.¹⁷ Although these practices are common, some researchers have advocated for removal of all dysplastic lesions regardless of the severity, as all grades have potential for transformation.²² If the histologic diagnosis does not correlate with the clinical findings, and concern for malignancy remains, then re-biopsy must be considered to rule out a false negative from the previous sample.

Failures in the diagnostic process run the risk of misdiagnosis and/or diagnostic delay with the potential for significant consequences. The present case illustrates the importance of consistent surveillance, the need for proper biopsy technique, and the use of clinical judgment when interpreting histopathology reports. An exophytic mass or a chronic, non-healing ulcer on the tongue or floor of the mouth requires biopsy to rule out malignancy. This maxim holds true even when prior biopsy has been completed. While high-risk dysplasia does not always progress to OSCC the finding of "hyperkeratosis and acanthosis with no evidence of epithelial dysplasia" in this case should be viewed with suspicion after a biopsy had already identified "moderate-severe dysplasia" within the same lesion.²³ The absence of dysplasia in the later sample is much more likely to be the result of site selection than a "reversal" of prior dysplasia. Furthermore, a histopathologic diagnosis of "hyperkeratosis" should be viewed with caution in otherwise suspicious lesions due to the potential of a false-negative result if the biopsy was obtained from a suboptimal site. Site selection is crucial to ensure a representative tissue sample for the pathologist's review. Proper sampling can be enhanced by providing larger tissue samples, sampling multiple sites, and/or using adjunctive tests such as toluidine blue to guide site selection.

Finally, it is noted that the third pathology report in this case recommended surgical removal of the lesion with clean margins due to the moderate-to-severe epithelial dysplasia and the need for a larger sample to rule out invasion. It raises the question of whether the partial glossectomy and selective neck dissection could have been avoided if an excisional surgery had been completed at that time.

This case highlighted the complex diagnostic process for high-risk oral lesions and the importance of surveillance, informed biopsy technique, and accurate interpretation of pathology reports to appropriately manage patients with potential oral malignancy.

Kevin Chung, DDS, MSD
Dental Oncology Fellow, Memorial Sloan Kettering Cancer Center, New York, New York; Affiliate Faculty, Department of Oral Medicine, University of Washington School of Dentistry, Seattle, Washington

David Dean, DDS, MSD
Clinical Associate Professor,Department of Oral Medicine, University of Washington School of Dentistry, Seattle, Washington; Faculty of Dental Surgery, Royal College of Surgeons of Edinburgh; Diplomate, American Board of Oral Medicine

Jasmine Olson, DDS, MSD
Clinical Instructor,Department of Oral Medicine, University of Washington School of Dentistry, Seattle, Washington; Diplomate, American Board of Oral Medicine

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