Picture quiz: Oral white patches

History

A 46 year old woman presented to her general practitioner with a history of painful oral ulcers. On examination of her mouth, her doctor saw a white patch on the floor of her mouth (fig). The general practitioner referred her to the local oral medicine department for further investigation and treatment. She was taking no drugs. She smoked 25-30 cigarettes a day and drank 20-22 units of alcohol a week.

Questions

1. What does the figure show?
2. What is the differential diagnosis?
3. How could you reach a definitive diagnosis?

Answers

1. The figure shows the front view of the mouth with the tongue raised. On the ventral (top) aspect of the tongue, you can see a diffuse white lesion which is slightly raised from the rest of the oral mucosa.
2. You can group white patches in a number of ways. Clinically, they can be separated depending on whether the lesion can be wiped away or not. In general, lesions which can be wiped away are due to accumulation of epithelial debris or inflammatory exudates. Lesions which cannot be wiped away are caused by abnormal or increased keratin production and are known as keratoses. These lesions appear white because they are soaked in saliva.
   Histologically, lesions can be divided into patches which show epithelial dysplasia and those which do not. The term dysplasia refers to the extent of cellular abnormality within the epithelial cells, such as abnormalities in proliferation, maturation, and differentiation of epithelial cells. This can range from mild to moderate to severe changes.
   Lesions can also be grouped depending on their cause, and this forms the basis of their clinical differential diagnosis. The clinical differential diagnosis of white patches based on their cause is as shown (table).
3. Incisional biopsy for histological examination is essential to get a definitive diagnosis. This means a small sample of the lesion is excised and sent for biopsy results; this is normally done under local anaesthetic. Biopsy will characterise the nature of the lesion and assess the degree of epithelial dysplasia from mild to moderate to severe. In other words, histological results show the potential malignancy of the white lesion. The more dysplastic the lesion, the more malignant potential it has. Furthermore, it will distinguish between white patch disorders, the most common being lichen planus and leukoplakia.

You should also do blood tests to exclude an underlying nutritional deficiency and you should do swabs and smears to exclude infection with Candida. On this occasion, biopsy revealed sublingual keratoses (leukoplakia due to smoking) with mild dysplasia.

Discussion

The term "white patch" is often used clinically to describe the appearance of lesions presenting as white areas on the oral mucosa. Lesions associated with abnormal or increased production of keratin are often described as keratoses. Oral keratoses are white because the thickened or abnormal keratin becomes hydrated as a result of being bathed by saliva and then evenly reflects light. A similar reaction is seen on palms and soles, after prolonged soaking or bathing in water.

A white patch is a particularly important clinical presentation, because it has been associated with malignancy. However, not all white patches are premalignant.

Leukoplakia

Leukoplakia is a white patch on the mucosa which cannot be rubbed off or characterised as any other definable lesion. It is therefore a diagnosis of exclusion and is clinically associated with the occasional development of carcinoma. Leukoplakia showing epithelial dysplasia is more likely to become malignant than one not showing any features of dysplasia--the more severe the dysplastic features the greater the risk for malignancy. However, leukoplakia lesions with moderate to severe dysplastic features may regress if the causes are stopped. Such causes include smoking tobacco and bad nutritional habits. The reported prevalence of malignant transformation in leukoplakia is variable.

Leukoplakias may be homogeneous in appearance, like in the figures, such as smooth, plaque-like, or non-homogeneous. Non-homogeneous lesions have a greater potential for malignancy. They show areas of redness, ulceration, and nodular thickening.

The site is also important in predicting malignant potential. Hard palate leukoplakias in smokers have a low malignant transformation rate, but those on the soft palate are more sinister. The most worrying site is the lateral border of the tongue and floor of the mouth, which is where most intraoral carcinomas arise.

Prevention and treatment

Biopsy sampling may not be representative, and being confident about the potential for malignancy of any lesion is difficult. Careful follow up is therefore necessary, and patients with persistent white patches should be reviewed every 3-6 months. If any sinister change is observed clinically--such as an increase in size of the lesion, ulceration, induration, fixation, lymphadenopathy, bone destruction, or pain--you need to biopsy again to ensure early diagnosis of any malignant lesion and also refer the patient to a specialist maxillofacial surgeon for early treatment. You should also encourage patients to avoid any risk factors such as smoking and heavy consumption of alcohol.

Prevention, screening, and early treatment of moderate to severe dysplastic lesions are essential to reduce the incidence of oral cancer.