Interpretation
Squamous cell carcinoma of the third eyelid, with likely metastasis to the kidney and secondary necrosis
Explanation
The aspirate of the kidney mass was minimally cellular and contained predominantly large swaths of necrotic debris and degenerating cells (Fig 1A). There were low numbers of individualized polygonal cells with variably-sized nuclei and cytoplasm that ranged from turquoise to light blue to dark grey. Often these cells had very prominent angular cytoplasmic margins and perinucleuar vacuolization (Fig 1A-B). There were also low numbers of inflammatory cells, predominantly nondegenerate neutrophils with a few debris-laden macrophages.
The aspirate from the third eyelid swelling was highly cellular and contained a pleomorphic population of epithelial cells arranged in small clusters and as individualized cells admixed with low numbers of inflammatory cells (Fig 2A). The cells ranged in shape from cuboidal to large and polygonal with angular borders. Cytoplasmic edges were well defined and cytoplasm ranged from blue to glassy and turquoise. Nuclei were round with condensed chromatin to large and oval with stippled to vesiculated chromatin. The larger nuclei had prominent, variably-sized nucleoli that occasionally had angular margins. Some of the cells were accumulating melanin pigment (Fig 2B). Anisocytosis and anisokaryosis were moderate overall and a small proportion of the cells displayed marked atypia. Perinuclear to diffuse vacuolization was noted. The inflammatory cells were predominantly nondegenerate neutrophils with rare lymphocytes noted. The background was mildly bloody. Streams of nuclear material were found in pillowy aggregations between the epithelial cells.
The aspirate of the third eyelid swelling was interpreted as a carcinoma, with squamous cell carcinoma as the leading differential diagnosis. An adenosquamous carcinoma could not be excluded based on cytologic features alone. When viewed in conjunction with the aspirate from the third eyelid swelling, the renal lesion was interpreted as a metastatic carcinoma with necrosis and mixed inflammation.
Case follow-up
Histopathology of the third eyelid mass was not obtained. Thus, the squamous cell carcinoma may be arising from the conjunctival tissue or the ducts within the gland. This is a very rare tumor in this location in the dog. A glandular tumor with squamous differentiation is also possible, but cytologically there was no evidence of acinar-like arrangements. The owners pursued palliative care.
Case Answers
1: Great question! Traditionally, there are four type of carcinoma that can arise from the transitional cells of the renal pelvis; transitional cell carcinoma, squamous cell carcinoma, adenocarcinoma and undifferentiated carcinoma. None of these lesions have been reported to metastasize to the third eyelid. Conversely, there are very few documented cases of third eyelid squamous cell carcinoma, so predisposed sites of metastasis would be speculative at this point.2 Hence, this is a question we can only speculate about at this time (in the author’s opinion, the third eyelid mass was likely primary).
2: There has been a report of a primary squamous cell carcinoma arising from the renal pelvis in an 18 year old dog. The authors classified the lesion as squamous cell carcinoma of the transitional epithelium, because of the formation or keratin pearls (speaks towards squamous differentiation) and immunoreactivity for cytokeratin 8 (which was deemed evidence of transitional cell origin).1 Without the third eyelid mass, a primary lesion (transitional cell carcinoma) involving the renal pelvis should be considered. The squamous nature of the cells could be due to metaplasia secondary to the inflammation, or indicative of neoplastic transdifferentiation.
Third eyelid tumors
Adenocarcinoma of the third eyelid is rare and can be mixed in nature with a myoepithelial component. In a retrospective evaluation that included 127 cases of eyelid gland neoplasms in the dog, adenocarcinomas accounted for 85%, followed by adenomas (14.2%) and squamous cell carcinoma (0.8%). Of the 62 cases with follow-up, only 8.1% had confirmed or suspected metastasis.2 Primary tumors of the third eyelid can arise from conjunctival surfaces, lymphoid tissue, stromal (including myoepithelial component), or the glandular tissue.3
References
- Dagli ML, Calderaro FF, Silva MT, Guerra JL. Squamous cell carcinoma of the renal pelvis with metastasis in a dog. J Comp Pathol. England; 1997 May;116(4):397–402.
- Dees DD, Schobert CS, Dubielzig RR, Stein TJ. Third eyelid gland neoplasms of dogs and cats: a retrospective histopathologic study of 145 cases. Vet Ophthalmol. England; 2016 Mar;19(2):138–43.
- Miyazaki A, Yonemaru K, Hirata A, Yanai T, Sakai H. Histopathological and immunohistochemical features of atypical epithelial tumours of the gland of the third eyelid in seven dogs. J Comp Pathol [Internet]. Elsevier Ltd; 2015;152(4):299–303. Available from: http://dx.doi.org/10.1016/j.jcpa.2015.03.001
Authored by: Dr. Behling-Kelly
