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B-cell lymphoma with Mott cell differentiation in a cat
Tomomi Kanehara1, Naoko Matsui2, Mami Murakami2,3,4
1Laboratory of Veterinary Pathology, Gifu University, Gifu, Japan.
Insights
This study reports the first diagnosed case of B-cell lymphoma with Mott cell differentiation in a cat. This rare feline cancer involves neoplastic lymphoid cells with unique cytoplasmic inclusions.
Area of Science:
- Veterinary Pathology
- Oncology
- Immunohistochemistry
Background:
- B-cell lymphoma is a common malignancy in cats.
- Mott cell differentiation, characterized by cytoplasmic inclusions of immunoglobulin, is rare in feline lymphoid neoplasms.
- This case presents a unique manifestation of feline lymphoma.
Observation:
- A 12-year-old Domestic Shorthair cat presented with anorexia and vomiting.
- Physical examination revealed enlarged tonsils and lymph nodes, and a submucosal epiglottic mass.
- Cytologic and histopathologic examinations showed medium- to large-sized neoplastic lymphoid cells with cytoplasmic inclusions.
Findings:
- Immunohistochemistry confirmed a B-cell immunophenotype (CD20+, Pax5+, MUM1+, CD3-).
- The cytoplasmic inclusions stained positive with Periodic Acid-Schiff (PAS) and contained immunoglobulin M (IgM) and lambda (λ) light chains.
- These inclusions are consistent with aberrant IgM λ light chain accumulation, similar to Russell bodies, leading to a diagnosis of B-cell lymphoma with Mott cell differentiation.
Implications:
- This is the first documented case of feline B-cell lymphoma with Mott cell differentiation.
- Understanding this specific subtype can improve feline lymphoma diagnosis and classification.
- Further research may elucidate the pathogenesis and treatment strategies for this rare condition in cats.
Abstract:
A 12-year-old, male castrated Domestic Shorthair cat was presented to Animal Medical Center of Gifu Univeristy with anorexia and vomiting. Physical examination revealed an enlarged left tonsil and right mandibular lymph node (approximately 2-3× the normal size), and a submucosal mass on the right side of the epiglottis (1.5 × 2.0 cm). On computed tomography images, an enlarged left tonsil, and enlarged right mandibular, right pharyngeal, and left and right cervical lymph nodes were observed. Cytologic examination of smears of tonsil and lymph nodes revealed numerous medium- to large-sized neoplastic lymphoid cells, approximately half of which contained one or several light-blue homogenous globoid cytoplasmic inclusions (5-10 μm), which stained magenta with periodic acid-Schiff (PAS) stain. Histopathologic examination of the left tonsil revealed diffuse proliferation of medium- to large-sized neoplastic lymphoid cells effacing the original lymphoid architecture. Half of the cells contained one or several eosinophilic globoid cytoplasmic inclusions, which stained magenta with PAS and showed positive immunohistochemical reactions for immunoglobulin M (IgM) and λ light chain. Neoplastic lymphoid cells were also CD20+ , Pax5+ , and MUM1+ , and CD3- . Thus, the neoplastic lymphoid cells expressed a B-cell immunophenotype, and the globoid cytoplasmic inclusions represented an aberrant IgM λ light chain accumulation, similar to Russell bodies. B-cell lymphoma with Mott cell differentiation was diagnosed based on cytologic, histopathologic, and immunohistochemical features. This is the first report of B-cell lymphoma with Mott cell differentiation in a cat.
