Study sharpens picture of ocular metastasis from feline lung cancer: full analysis

A new Veterinary Pathology case series puts a sharper histopathology lens on a rare but consequential feline cancer presentation: intraocular metastatic carcinoma presumed to arise from the lung. The study, by Hannah Stocklein, Ryan P. Taylor, and Gillian C. Shaw, reviewed feline ocular biopsy submissions from 2019 to 2025 and focuses on the histomorphologic and immunohistochemical features that may help distinguish these lesions when cats present with eye disease before a full oncologic picture is clear. (acvp.org)

That matters because feline pulmonary carcinoma is uncommon overall, but it has a well-recognized tendency to metastasize in unusual ways. Earlier literature has linked primary lung tumors in cats to metastases in digits, skeletal muscle, skin, distal aorta, and the eye, prompting some authors to broaden the classic “lung-digit syndrome” framing to “MODAL syndrome” to reflect the wider metastatic pattern. In a 2020 necropsy-based study, 13% of cats with metastatic disease had ocular metastases, and after lymphoma, pulmonary carcinoma was among the most common tumor types affecting the eye. (journals.sagepub.com)

The most concrete details available publicly come from an American College of Veterinary Pathologists conference abstract describing an overlapping earlier cohort from 2019 to 2023. In that report, 11 cases met inclusion criteria. Uveitis, glaucoma, and an ocular mass were the leading clinical presentations. Ten of 11 cats had a thoracic mass identified radiographically before enucleation, and 3 of 10 had presumed metastatic lung disease already recognized. Histologically, all neoplasms had epithelial arrangements, 8 of 11 showed “carpeting” behavior, and the anterior uvea was involved in 9 of 11 cases. Alcian blue highlighted goblet cells in 4 of 11 cases, while TTF-1 labeling was present in only 2 of 11, with no overlap between goblet-cell-positive and TTF-1-positive cases. Average survival after enucleation was 34 days among nine cats with follow-up. The newly published paper appears to extend that work through 2025 and adds vimentin to the immunohistochemical profile, based on the article title and source metadata. (acvp.org)

The study builds on a small but important body of ophthalmic pathology literature. A 2001 report of four cats with angioinvasive pulmonary carcinoma and ocular metastasis described ischemic chorioretinopathy, vascular occlusion, and widespread metastatic disease, suggesting that ocular changes may reflect vascular tumor embolization rather than only mass effect. A Joint Pathology Center teaching case similarly noted that intraocular metastases in cats often involve the posterior uvea because of its rich blood supply, even though the newer COPLOW series found frequent anterior uveal involvement in its selected cases. That difference may be clinically useful: it suggests ocular metastasis can present with more than one dominant anatomic pattern, depending on when the eye is sampled and how the lesion evolves. (pubmed.ncbi.nlm.nih.gov)

The immunohistochemistry angle is especially relevant for diagnostic labs. In feline pulmonary carcinoma more broadly, a 2023 Veterinary Pathology study found that pulmonary carcinomas show variable histologic subtypes and metastatic behavior, and reported absent Napsin A expression in feline tissue tested, highlighting the challenge of simply importing human pulmonary markers into feline diagnostics. Against that backdrop, the low TTF-1 positivity reported in the ocular metastasis series suggests veterinary pathologists may need to lean on a combined approach: clinical history, thoracic imaging, tumor architecture, special stains such as Alcian blue, and exclusion of other primary ocular or metastatic carcinomas, rather than expecting a single marker to settle origin in every case. (pubmed.ncbi.nlm.nih.gov)

Why it matters: For general practitioners, ophthalmologists, oncologists, and pathologists, the practical takeaway is that severe unilateral ocular disease in an older cat, especially uveitis, glaucoma, retinal change, or an intraocular mass, should keep metastatic carcinoma on the list, even if respiratory signs are absent. Prior reviews note that cats with primary lung tumors often present first with signs tied to metastasis rather than pulmonary disease itself, and prognosis is typically grave once distant spread is evident. Earlier pathology teaching material cites most cats with metastatic lung carcinoma dying or being euthanized within about six weeks of diagnosis, which aligns with the short post-enucleation survival reported in the COPLOW cohort. That makes early thoracic imaging and coordinated staging particularly important when ocular findings don’t fit more common inflammatory or primary neoplastic patterns. (askjpc.org)

Expert commentary specific to the new paper was limited in publicly accessible sources, but the broader specialty literature is consistent: ocular metastasis in cats is uncommon enough to be missed clinically, yet common enough within metastatic pulmonary carcinoma to warrant suspicion. Recent review literature on retinal and fundic manifestations of systemic disease in cats and dogs also reiterates that pulmonary carcinoma is one of the principal metastatic tumors affecting feline eyes. In practice, that supports a message many clinicians already know from lung-digit cases: when an older cat presents with a strange distal lesion, ocular lesion, or both, the chest deserves attention. (frontiersin.org)

What to watch: The next question is whether the full 2019-to-2025 publication provides a reproducible diagnostic panel or pattern set that can improve antemortem recognition across practices and pathology labs. If so, it could influence how veterinarians stage atypical feline eye disease, how pathologists word presumptive pulmonary origin in biopsy reports, and how quickly clinicians move from enucleation or ocular biopsy to thoracic imaging, oncology referral, and prognosis discussions with the pet parent. (acvp.org)