Abstract

Our collective understanding of the roles herpesvirus and papillomavirus have in the phases of development of cetacean oral and genital squamous cell carcinoma is still incomplete. Clinical detection of small early lesions of dolphin oropharyngeal papilloma/squamous cell complex relies on a close examination of the mucosa of the oral cavity with the tongue initially retracted to stretch the frenulum tissue caudally. The tongue is then elevated and gently moved laterally to each side to flatten the mucosa for inspection. Dorsal tongue evaluation may also show a wide range of lesions with easy-to-miss early characteristics.

Staging of the disease is dependent on recognition of visual changes that range from 1 mm lesions in the frenulum and the cranial surface of the lingual mucosa that appear as red dots which may resemble ecchymoses. If noted at this stage, these lesions may appear to come and go. There may be subtle generalized swelling of the frenulum with loss of rugal folds and increased horizontal creases, small ulcerations in the frenulum and tongue, and small “cauliflower-like” lesions in the mucosa. Lesions of the frenulum increase in size with scattered areas of thicker solid tissue involving the mucosa progressing to solid tumor masses that range from discrete to generalized tissue involvement. Lingual lesions may include the dorsum, caudal tongue base and lateral sides of the tongue with a mixture of ulcerations and elevated oval to irregularly raised surface lesions that tend to coalesce and increase in elevation as tumor masses develop under the mucosa. Ulceration and tumor growth may be found in the caudal hard palate either unilaterally or bilaterally (sometimes in a symmetrical pattern suggesting involvement with areas of lymph tissue) and the central area. Progression of lesions continues in both frenulum and lingual tissue with larger masses noted in surrounding tissue and potential metastasis to regional nodes. Regular close-up pictures should be taken of the frenulum, dorsal surface of the tongue, lateral tongue and caudal pharynx for more detailed inspection and comparison. A magnifying loupe may be helpful to identify early lesions. Any suspected changes should be noted on a hard copy sheet or photos annotated for future comparison to illustrate disease progression. Additional study of the occurrence of deeper tumors post-cryotherapy may be useful.

Initial biopsies should occur in the earliest recognized stage of the disease. Biopsy tissue should be divided into subsamples fixed in formalin for histopathologic and molecular histotechnological procedures formalin samples, subsamples frozen for PCR and qPCR, and subsamples for virological culture. To fully utilize new molecular techniques, such as RNAscope, and established approaches, such as immunohistochemistry, we need to adjust our sampling approach and limit formalin fixation of biopsy specimens to 24 hours, after which specimens should be processed into paraffin blocks to stop the degradation of genetic material and limit protein cross-linking. Other options may include substituting formalin with a non-cross-linking solution such as ethanol.

* Presenting author