What to Do When the Zebra Walks in the Door
What to do when the zebra walks in the door H.J. Lapointe
A. introduction: With the exception of relatively unusual geographic circumstances, the usual assumption that one may make about hoofbeats outside your window is that they are being made by a horse and not a zebra. In other words: common things happen commonly. This is true in dentistry where the majority (but not all!) of practice is dedicated to the detection, prevention and treatment of relatively few diseases. Dental caries, periodontal disease and trauma claim the lion’s share of problems that we are asked to deal with. Never the less, less common problems, ZEBRAS, occasionally come into the picture and impact on management. These zebras are the many and various diseases, tumours, hyperplasias, cysts and assorted lumps and bumps that make up the world of oral pathology. It is this world that I hope to explore, in small part, today.
B. Rationale: the reasons for occasionally revisiting this subject are straight forward. These are uncommon lesions that are easy to forget when we see them so infrequently. Despite this, we need some review and preparation for the day the zebra walks in, unannounced. Preparation for this unexpected event requires thinking ahead, organization and work in order to be of use. It requires:
1. prior knowledge of the look and feel of normal tissues
2. prior knowledge of the various diseases
3. a systematic approach for finding pathology
4. a systematic approach for identifying pathology
5. clinical tools or procedures for sampling or removing pathology
6. practice …
C. Objectives: our objectives for today’s discussion are the following:
1. To better understand how clinical behavior reflects the underlying disease process and how this impacts on the otherwise normal appearance and function of tissues.
2. To reveal the patterns of presentation of the various types of pathological lesions.
3. To review some common (and-not-so-common) lesions of the oral mucosa and jaws.
4. To use the process of data Interpretation and differential diagnosis to help definitively diagnose lesions of the mucosa and jaws.
5. To Illustrate and explain clinical techniques of incisional and excisional biopsy and removal of lesions such as mucoceles. epulis fissuratum, papilloma, fibroma, etc.
6. To allow participants to exercise their skills and participate In the formation of differential diagnoses for various oral lesions.
D. Biological Behaviour:
1.Normal: While initially somewhat obvious, the concept of what constitutes “NORMAL”, requires a little clarification. Normal must be understood as a spectrum of “normal variation”. Many factors impact on this variation and these include:
Age: infant, toddler, child, teen, adult, mature and elderly
race: African, Asian, European or American aboriginal
previous disease: caries, periodontal disease, cancer, trauma, infection
habits: oral hygiene, tooth brushing, bruxism, etc
These issues include such concepts as “normal healing”, “normal development”, “normal sequelae”, etc. Despite this variation and the factor that impact on it, the implication is clear...”normal” is what we commonly expect to see and per se does NOT require further investigation or further management.
2. Abnormal: In contrast, abnormal implies that there is something unusual or different about the situation. Initially we see or feel something different from usual and, most importantly, the implication is that the “lesion” will behave differently. It is this abnormal behavior of pathoses that trouble us the most. Whether this behavior is swelling, nerve invasion, causation of pain, metastasis or destruction of bone, it is this “BAD” behavior that we want to either stop or prevent by intervention. The basis of “bad” behavior is the underlying structure and “pathophysiology” of the lesion. How does underlying biology drive clinical behavior and therefore presentation?
3. Clinical presentation: In order to explore these issues, we will look at comparing the examples of cancer and Infection. In the case of cancer, the growth, invasion, and metastatic potential of the tumour are a function of aberrations in the mechanisms of cell division and adhesion that allow uncontrolled cell division and encroachment of the cells on normal tissue. In the case of infection, pain, swelling and fever are the result of the multiplication of micro-organisms, the production of endo- and exotoxins and very importantly, the host’s response to bacterial invasion.
In both of these cases, the knowledge of the underlying mechanisms of causation and progression of disease allow us to detect, classify and treat the problems. The management of such a case begins with the patient presenting with a problem. Interpretation of the “facts” we gather about the case allows us to place the “lesion” within a biological context and begin working toward the diagnosis.
a. History: We start with the story told by the patient: the history of a cancerous lesion differs from that of an infection and this reflects the underlying biology for the two diseases. The tumour is usually relatively slow growing, usually painless and is often noticed when it interferes with function, causes numbness or problems with denture fit (for example). In contrast, infection is usually rapid, painful and associated with a clear cut etiology: a hole in a tooth, post op wound or impacted tooth.
b. Examination findings: Following through with these examples, examination findings also differ but are consistent with the cellular and tissue behavior of the lesions. Tumours often present as lumps with ulceration or rough margins, In Contrast, infection may be much less discrete and the associated host response (inflammation) indicates a different process of pathological progression.
The use of these two examples illustrates the organization and the type of information that allows us to categorize and manage clinical entities. We listen to the patient’s story or history of chief complaint and we then correlate that information with the information gathered by clinical examination. These two sources of information give us a sense of the disease process, whether it be:
inflammatory, traumatic, neoplastic, congenital or developmental,
4. Differential diagnosis: Having listened to the story and looked at the lesion, we are now in a position to start thinking about diagnosis. Often we are faced with entities that may prove to be one of many things. The list of the “many things” is the differential diagnosis.
The differential diagnosis is a list of the possibilities in the order of likelihood.
Once established, the differential diagnosis is available as a tool to help direct further investigation in order to rule in or rule out items on the list. These investigations include further imaging, blood tests, biopsy and so on.
5. Review of pathology: Rather than review diseases through textbook classifications, I have elected to look at them where they live: in the tissues of the mouth. What I hope to do is look at the process of formation of a differential diagnosis for some typical clinical problems and then some of the steps that need to be taken in order to determine the definitive diagnosis. Examples of classical differentials include: a lump on the gingiva, a lump in the mucosa, mucosal change, an ulcer on the mucosa and a radiolucency in the mandible.
a. Lumps on the gums: epulis fissuratum, peripheral giant cell granuloma, peripheral ossifying fibroma, pyogenic granuloma, malignancies
b. Lumps in the mucosa: traumatic fibroma, lipoma, schwannoma. benign and malignant salivary gland tumours
c. Mucosal change: hyperkeratosis, lichen planus, dysplasias, carcinoma
d. Ulceration of the mucosa: traumatic ulcer, erosive lichen planus. pemphigoid, syphillis, squamous cell carcinoma
e. Radiolucencies in the jaw: radicular cyst, traumatic bone cyst, dentigerous cyst, central giant cell granuloma, odontogenic keratocyst, ameloblastoma
6. Tools for sampling or removing pathology...incisional and excisional biopsy
a. Characteristics of a good biopsy: in order to maximize the ability of the diagnostic pathologist to return to you an accurate diagnosis of the lesion, there are certain characteristics of the ideal biopsy that have to be met:
- the specimen must contain a sample of the abnormal tissue
- the specimen must contain a sample of the normal tissue
- there must be minimal artifact or damage to the sample
b. Incisional biopsy: this technique is used to sample a large lesion without completely removing it. An edge or corner of a lesion is removed (along with normal tissue) with the intent of establishing a diagnosis and then returning for definitive treatment (or no treatment!).
c. excisional biopsy: this technique allows for sampling a lesion with the intent of treating the lesion by completely removing it.
These techniques can be applied to a variety of clinical entities and are important tools in the overall management of oral pathology.