Department of Oral Pathology, Radiology, & Medicine
--- Educational Resources
The Oral Pathology case studies were provided by Dr. Gilbert E. Lilly. Dr. Lilly was an outstanding teacher and believed that diagnosis of oral lesions should be accomplished using a logical, well thought-out approach.
Diagnosing lesions of the oral mucosa is necessary for the proper management of patients. Clinical differential diagnosis is the cognitive process of applying logic and knowledge, in a series of step-by-step decisions, to create a list of possible diagnoses. Differential diagnosis should be approached on the basis of exclusion. All lesions that cannot be excluded represent the initial differential diagnosis and are the basis for ordering tests and procedures to narrow the diagnosis. Guessing what the one best diagnosis is for an oral lesion can be dangerous for the patient because serious conditions can be overlooked.
The first decision to make when diagnosing soft tissue lesions of oral mucosa is to determine if the lesion is a surface lesion or soft tissue enlargement.
Surface lesions of oral mucosa consist of lesions that involve the epithelium and superficial connective tissue of mucosa and skin. They do not exceed 2-3 mm in thickness. Surface lesions are divided into three categories based on their clinical appearance: white, pigmented, and vesicular-ulcerated-erythematous.
Soft tissue enlargements are swellings or masses that are divided into two categories: reactive enlargements and tumors.
Reactive soft tissue enlargements are caused by injury, such as infections, physical trauma, chemical trauma, or allergic reactions. Reactive soft tissue enlargements usually have a rapid onset (short duration) and may increase and decrease (fluctuate) in size and usually eventually regress. Reactive enlargements are often, but not always, tender or painful and usually have a more rapid growth rate (measured in hours to weeks) than tumors. Sometimes patients with reactive enlargements will be able to report the source of injury. Sometimes reactive lesions are associated with tender lymph nodes and systemic manifestations, such as fever and malaise. Once it is decided that a soft tissue enlargement is reactive, the next step is to determine what the cause of the lesion is.
Soft tissue tumors are characterized by being persistent and progressive; they do not resolve without treatment. They are usually not painful early in their development, and the growth rate varies from weeks to years. The term tumor is used in the clinical sense of an enlargement and is not necessarily a true neoplasm. For example, irritation fibroma is caused by chronic irritation but is classified as a tumor because this lesion is persistent and progressively increases in size.
If a soft tissue enlargement appears to be a tumor, the clinician must next determine if the enlargement is benign or malignant. Benign tumors are typically better defined or circumscribed and have a slower growth rate, measured in months and years, than malignant neoplasms. Malignant neoplasms are more likely to be painful and cause ulceration of the overlying epithelium than benign lesions. Since malignant neoplasms invade or infiltrate surrounding muscle, nerve, blood vessels, and connective tissue, they are fixed or adherent to surrounding structures during palpation. Some benign tumors are also fixed to surrounding structures, but others are surrounded by a fibrous connective tissue capsule, which may allow them to be moved within the tissue independent of surrounding structures. If located in the area of teeth, benign tumors are more likely to move teeth, while malignant lesions loosen teeth.
Benign tumors can be subdivided into four categories: epithelial, mesenchymal, and salivary gland tumors, and cysts of soft tissue. Because soft tissue tissue cysts are well cirscumscribed, slowly growing, persistent, and progressive, they have historical and clinical features resembling those of benign tumors.
It should be emphasized that the clinical descriptions above are general guidelines, and exceptions occur. Removal of the lesion and microscopic examination of the tissue is often the only way to arrive at a definitive diagnosis.