An 11-year-old, female, spayed labrador retriever was presented to the Iowa State University Oncology Service for evaluation of a rapidly expanding mass located near the right prescapular lymph node. A Patnaik grade I mast cell tumour (mitotic index <3/10 high-power fields) had been completely excised from the right antebrachium five months before presentation. Cytological evaluation of aspirates from the healed incision site and the new mass revealed mast cells with marked eosinophilic infiltration consistent with local recurrence and presumed lymph node metastasis. A complete blood count revealed markedly elevated eosinophils (23.96×103 cells/µl, reference interval 0–0.75). The patient was diagnosed with a histologically low-grade, biologically high-grade cutaneous, metastatic mast cell tumour with paraneoplastic hypereosinophilia. Changes in the magnitude of peripheral hypereosinophilia frequently paralleled tumour response to treatment with multiple antineoplastic agents. Nine months after initiating chemotherapy, treatment was discontinued due to declining quality of life.
- mast cell tumor
- paraneoplastic Syndrome
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Contributors MM contributed to the data collection, analysis of the data and writing of the manuscript. EB contributed to the management of the case, data collection and writing of the manuscript. HAF evaluated the clinical pathology data and contributed to the writing of the manuscript. LF contributed to the management of the case and writing of the manuscript. CMJ contributed to case management, data collection and preparation of the manuscript. All authors reviewed the final version of this manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests CMJ is a former employee of Pfizer Animal Health and has served as a member of the Zoetis (formerly Pfizer Animal Health) Oncology Advisory Board and occasionally receives honoraria for these activities.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement This is a descriptive case report and therefore all data generated has been included in the manuscript.
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