Features of Canine Conjunctival Melanocytic Tumors Reilly CM, Dubielzig RR, Newman SJ and Bergman PJ

Purposes  A retrospective study of the histologic and biologic features of canine conjunctival melanocytic tumors  Compare to results of prior studies  Biologic behavior and histologic characteristics of canine conjunctival melanomas. Collins BK, Collier LL, Miller MA, Linton LL. Prog in vet and comparative ophthalmology; 3: , 1993.

Methods  Cases of conjunctival melanocytic tumors selected (COPLOW and AMC)  Follow-up surveys mailed to submitting ophthalmologists  Only cases with follow-up available were included

Methods (cont.)  Slides were evaluated for:  Pigmentation  Intra- and subepithelial packeting  Criteria of malignancy  Cell type(s)  Mitotic index  Necrosis  Epithelial dysplasia

Methods (cont.)  Survey information included:  Breed, gender, age at diagnosis  Tumor location (bulbar, TEL, palpebral)  Surgery type (incisional, excisional, enucleation, exenteration)  Recurrence, metastasis and death

Results  63 cases were identified  24 had follow-up available  14 males, 10 females  8 mixed breeds, 3 labs, 2 cockers, 2 Weimaraners, 2 Shar-peis  1 each Schnauzer, German Shepherd, Poodle, Golden Retriever, Boston Terrier, Pekingese, Newfoundland  Age at diagnosis 6-14 y (11.5)

Results – Location  14/23 (61%) on TEL  5/23 (22%) on bulbar conjunctiva  4/23 (17%) on palpebral conjunctiva  Location not provided for one tumor

Results - Histologic patterns  14/24 (60%) had packeting of neoplastic cells within conj. epithelium  19/24 (83%) had packeting in subepithelial stroma  No correlation with recurrence or metastasis  Can be helpful in diagnosis of amelanotic tumors

Results – Benign tumors  3/24 (12%) histologically benign (melanocytomas)  None had necrosis, mitoses or dysplasia  None recurred or metastasized  One was multicentric at diagnosis

Results - malignant  17/21 (81%) at least partially pigmented  5/21 (24%) were spindle cell type  7/21 (33%) were “epithelioid” type  9/21 (43%) were a mixture of both

Results - Recurrence  10/21 (48%) tumors recurred  4/12 (33%) TEL tumors  2/10 (20%) w/ marginal excision  2/3 (67%) w/ complete TEL excision  2/4 (50%) bulbar tumors  3/4 (75%) palpebral tumors  One tumor (TEL) had multicentric recurrence

Results – Tumor related death  Only 2 tumors (10%) metastasized  Both from palpebral conjunctiva  1 dog (5%) euthanized for aggressive regrowth  Also from palpebral conjunctiva  No dogs with TEL or bulbar tumors died from tumor  Palpebral tumors more advanced at diagnosis?

Conclusions  Similar to prior report EXCEPT:  Even male: female ratio  Shar-peis also over represented  Metastatic risk may be lower (10% v. 17%)  Recurrence even with aggressive surgery  Stresses the need for assertive follow-up  Especially rare diseases

Acknowledgements  Co-authors: Dr. Dick Dubielzig, Rebecca Morris, Dr. Shelley Newman, Dr. Phillip Bergman  Technical Assistance: Kate Leiber

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