Tangchang W, et al. J Vet Sci. 2022 Oct;23:e89. https://doi.org/10.4142/jvs.22124

Feline inferior tricholemmoma is a benign hair follicular tumour with minimal outer root sheath differentiation. The diagnosis is rarely suggested clinically, and this may contribute to frequent underrecognition by the histopathologist. A spayed female Munchkin cat exhibited a subcutaneous growth of a mass, 1.7 cm in diameter, located on the neck region. Histological examination revealed that the sole tumour consisted of clearly defined circular lobules, demonstrating a well‐developed basement membrane, a cuboidal or columnar morphology, and a vacuolated and/or pale eosinophilic cytoplasm. Additionally, these cells displayed round to ovoid nuclei with a peripheral palisade arrangement, which could be diagnosed as feline inferior tricholemmoma. Moreover, the tumour cells showed extremely positive staining for periodic acid–Schiff, immunoreactive SRY sex determining region Y‐box 9 (Sox9), and CD34. In this case, the diagnosis was established based on histological characteristics and supported a definitive diagnosis originating from cells with distinctive Sox9 and CD34 expression.

Cryptococcus neoformans is an opportunistic fungal pathogen causing severe infections in immunocompromised individuals. Arginine metabolism is critical for immune regulation, but its precise role in cryptococcal pathogenesis is not well understood. In this study, we investigated systemic and tissue-specific alterations in L-arginine metabolism during pulmonary C. neoformans infection and evaluated L-arginine supplementation as a potential therapy using a murine model. Key assessments included fungal burden quantification, inflammatory cell and cytokine characterization, brain gene expression analysis, histological examinations, and survival studies. We found significant depletion of serum L-arginine and its downstream metabolites, accompanied by increased arginase activity in infected tissues, indicating a disrupted metabolic balance. Gene expression analysis showed distinct metabolic shifts, including upregulation of arginase-1 (Arg1) and proline metabolism genes, with concurrent suppression of nitric oxide synthase 2 (Nos2) in the brain during the late infection phase. Oral L-arginine supplementation significantly reduced fungal burdens in the brain and spleen, suggesting its effectiveness in controlling cryptococcal dissemination from the lungs. Consequently, L-arginine administration improved survival and clinical scores while also reducing brain cryptococcoma in infected mice. Mechanistically, L-arginine enhanced protective immune responses within the mouse brain, facilitated microglial-mediated clearance of Cryptococcus, and reduced cryptococcal invasion across brain endothelial cells in vitro. In summary, oral administration of L-arginine mitigates C. neoformans dissemination by augmenting brain's immune response. This study provides crucial insights into arginine metabolism in cryptococcal disease progression, supporting L-arginine as a promising immunomodulatory therapy.

A male Korean raccoon dog of unknown age was rescued and placed at the Daejeon Wildlife Rescue Center, Korea. Physical examination revealed severe emaciation and dehydration, as well as thick crusts and alopecia over most of the body. During medical care, the animal died and was submitted for postmortem examination. Firm, brown-red lesions of various sizes were observed on the surface of the lungs. In cross-sections of the lungs, pulmonary vessels were thickened and dilated, with white irregular papillary luminal projections. Histologically, pulmonary blood vessels were severely hyperplastic, characterized by thickened dilated walls and fibrous papillary projections covered with a single layer of endothelial cells (ECs). Hyperplastic fibrous connective tissue was confirmed by Masson trichrome staining. The ECs expressed CD31. We diagnosed the lesion as intravascular papillary endothelial hyperplasia, a unique non-neoplastic reactive process that has not been reported previously in pulmonary vessels of canids, equids, or felids, to our knowledge.

A seven-year-old spayed female dog presented with multiple, small oval-shaped masses on the abdominal skin. The excised tissue was submitted for histopathological evaluation. Routine histology revealed basaloid nodules with stippled chromatin and pleomorphic nuclei. Morphologically, the tumor resembled a solid papillary carcinoma of the breast or an endocrine mucin-producing sweat gland carcinoma (EMPSGC). EMPSGC is a rare neuroendocrine-differentiated neoplasm. This study aimed to compare different immunohistochemical markers for distinguishing between canine sweat gland carcinoma (SGC) and mammary gland carcinoma (MGC). CK19 and Sox9 were useful in identifying SGC. Additionally, the tumor was positive for CK5, AE1/AE3+CK8/18, p63, vimentin, E-cadherin, and synaptophysin, while estrogen receptor staining was negative. The final diagnosis of canine EMPSGC was based on the tumor’s morphological and neuroendocrine immunohistopathological features. Our report provides the first detailed description of a canine EMPSGC, an exceedingly rare tumor in dogs.

Hyeon-Cheol Kim, Warisraporn Tangchang, Hwa Young Son, Bae Keun Park. Korean J. Vet. Serv. 2026;49:279-85. https://doi.org/10.7853/kjvs.2026.49.3.279