June 2009
Dr Gerhard Steenkamp

This 6-year old dog presents to you with a fungating mass directly associated with the ?carnassial tooth.  Radiographic examination reveals no bone destruction in the adjacent alveolus (tooth carrying bone).

1)  Give a differential diagnosis of this pathology
2)  Explain how you will finalize your diagnosis
3)  What are the treatment options for this lesion?

Answers:

1)  In a case such as this, the mass could represent anything from granulation tissue such as a pyogenic granuloma, a reactive lesion on the gingiva associated with trauma or poor oral hygiene, to benign or malignant neoplasms such as squamous cell carcinoma or even an amelanotic melanoma.

2) There is only one way to diagnose a pathological lesion such as this and that is by taking an optimal tissue biopsy and sending it for histopathology by a pathologist.  In this case the tumour turned out to be a well-differentiated squamous cell carcinoma with no bone involvement.

When taking a biopsy, the best results are usually obtained when the surgeon takes his/her biopsy at the margin between clinically normal and clinically abnormal tissue in the case of an ulcer or several deep fragments from within a tumour mass such as the one in the picture.  This is because sometimes only granulation tissue, which is also present in superficially traumatised areas of a malignant mucosal neoplasm as well as in ulcerated tumours, are biopsied and therefore not representative of the neoplasm. 

Some malignancies are known for its tendency to have large areas of tumour necrosis which also makes diagnosing impossible for the pathologist.  If the pathology report does not agree with your clinical impression either phone the pathologist and discuss this with him/her or re-biopsy the tumour in different areas.

3) Squamous cell carcinoma of the oral cavity (OSCC) is a malignancy with a grave prognosis unless diagnosed at an early stage and treating it by complete excision of the tumour, as confirmed by a respectable pathologist.  Tumours should never be cut or scraped out in small pieces and thrown away because you “feel” is that it has been removed completely.

Grading of OSCC should be done on the deepest infiltrating front of the tumour where single cell infiltration is sometimes seen extending into the deep surgical margin which had a clinically normal appearance. Adjuvant chemotherapy and/or radiotherapy should be decided on depending on the histological grading of the tumour, the presence or absence of metastatic disease as well as whether or not the excision margins were clear on microscopic examination. 

The amount of bone that needs to be removed, that is either none or a complete excision of the involved jaw, is dependant on the extend of bone involvement on radiographic examination and again histological confirmation. Care should be taken when there is any possibility that the intrabony nerves such as the inferior alveolar nerve in the mandible is involved as this might lead to metastatic disease proximal or distal to the affected area.  Treatment should be modified to accommodate this accordingly.