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Neurolymphomatosis is a very rare form of nervous system infiltration by lymphoma that can affect cranial and peripheral nerves and spinal nerve roots. The clinical appearance can mimic autoimmune or paraneoplastic neuropathies. To date, only 2 cases of neurolymphomatosis have been reported in the veterinary literature (1 dog and 1 cat). A case of neurolymphomatosis in a 5-year-old female Domestic Shorthair cat is reported. Two, whitish, bosselated, non-symmetric masses (1 cm × 1.2 cm × 0.5 cm) that incorporated almost all cranial nerves and semilunar ganglia occupying the basisphenoid depression were histologically composed of a proliferation of monomorphic lymphocytes. These lymphoid cells were positive for CD3 (T-cell lymphoma). Nested polymerase chain reaction detected feline leukemia provirus. Fragment analysis of feline T-cell receptor (TCR) gene rearrangements evidenced an oligoclonal pattern with few peaks of similar height. The integration of pathologic with biomolecular findings adds to the information concerning the role of Feline leukemia virus on TCRγ rearrangements in cases of feline lymphoma.

A well-demarcated mass was found by computed tomography in the left cerebellar hemisphere of a 4-year-old male Boxer with acute onset of progressive central vestibular syndrome. At necropsy, the pink, gelatinous mass was in the flocculonodular lobe. Histologically, neoplastic tissue arose from the granular layer of the cerebellar cortex and consisted of sheets of oval to round hyperchromatic cells, consistent with the diagnosis of medulloblastoma. Synaptophysin and neuron-specific enolase immunoreactivity supported the neuronal origin of the neoplastic cells; furthermore, a weak to moderate c-kit expression was detected, as reported in pediatric medulloblastoma. Telomerase activity of tumor cells was demonstrated by immunohistochemistry and by the telomere repeat amplification protocol, suggesting involvement of this enzymatic pathway., (© The Authors 2011)

The aim of this study was to investigate epidermal growth factor receptor (EGFR) expression in feline cutaneous squamous cell carcinoma (FC-SCC) and assess its prognostic role. Nineteen formalin-fixed paraffin-embedded excisional biopsies of FC-SCC were tested for EGFR expression using immunohistochemistry (IHC). Relationships between EGFR expression and histopathological parameters (differentiation, mitotic activity), disease-free interval (DFI) and overall survival (OS) at 24 months were further investigated. Fourteen of 19 tumours (73.7%) were positive for EGFR, with great variation in intensity and proportion of labelled cells. EGFR expression was not correlated with tumour differentiation or mitotic activity. Nine cats (47.4%) died of tumour-related causes. Patients with EGFR-positive tumours had a significantly worse outcome (P=0.0217), with decreased DFIs (P=0.0075) and survival times (P=0.0391). These data suggest that EGFR expression carries a negative prognostic significance in FC-SCC. EGFR inhibitors in association with conventional treatments may improve outcome for the subgroup of cats with EGFR-positive tumours., (Copyright © 2010 ISFM and AAFP. Published by Elsevier Ltd. All rights reserved.)

A 12-year-old, neutered male, mixed-breed, domestic cat was presented for dysuria and haematuria accompanied by recurrent dyschezia and constipation. At rectal digital examination a non-painful, globose and relatively immobile mass was detected at the pelvic brim, ventral to the rectum. Abdominal ultrasound showed the prostate replaced by a mass with a regular shape but patchy/non-uniform echogenicity. A prostatectomy followed by prepubic urethrostomy was performed. At histopathology the tumour was composed of epithelial ducts and acini with malignant features, surrounded by proliferating cellular stroma with mitoses and nuclear atypia; an immunohistochemical panel confirmed the biphasic nature of the tumour proliferation. The diagnosis was non-infiltrating malignant mixed tumour, resembling human sarcomatoid carcinoma of the prostate. Two years after surgery the animal has not shown any health problems. To the author's knowledge, this is the first reported case of prostatic tumour with a positive follow-up after surgical treatment in cat., (Copyright 2009 ESFM and AAFP. Published by Elsevier Ltd. All rights reserved.)

Deciduoid mesothelioma is a rare variant of epithelial mesothelioma, up to now only described in human pathology, which bears remarkable cytomorphologic resemblance to the endometrium of pregnancy, termed decidua. A case of peritoneal mesothelioma with deciduoid features in a 10-year-old, female dog is reported. Multiple whitish-gray nodules (1-5 mm in diameter) in parietal peritoneum and mesentery were histologically composed of large, proliferating, polygonal or ovoid cells with an abundant eosinophilic, glassy cytoplasm. Immunohistochemical evaluation indicated that the neoplastic cells coexpressed cytokeratin and vimentin with strong and diffuse cytoplasmic staining, and ultrastructural analysis showed long and slender mesothelial-type microvilli; these findings confirmed the mesothelial origin of the tumor.

Thirty-one canine cutaneous masses, diagnosed as mast cell tumors (MCT) by histopathologic analysis, were used to evaluate the immunohistochemical pattern of expression of KIT protein (CD117), a type III tyrosine kinase protein involved in mast cell growth and differentiation. Lesions were graded as I (well differentiated), II (intermediate differentiation), or III (poorly differentiated) according to the following morphologic features: invasiveness, cellularity and cellular morphology, mitotic index, and stromal reaction. Immunohistochemical KIT expression was compared with histologic grade and some histomorphologic features (cell differentiation and nuclear grade) evaluated separately. A possible predictive role of biologic behavior in MCTs for KIT expression was also investigated. Immunohistochemical analysis revealed three different patterns of KIT expression: a cytoplasmic diffuse pattern, a membranous pattern with immunostaining located on the cell surface, and a cytoplasmic perinuclear pattern, where KIT expression was detected in the cytoplasm of the neoplastic mast cells, close to the nucleus. Statistical analysis showed a close relationship between different KIT immunohistochemical patterns and histologic grade (P < 0.00000), cell differentiation (P < 0.00000), and nuclear grade (P < 0.0024). According to Kaplan-Meier-estimated survival curves compared by survival analysis, KIT expression was significantly associated with survival time (P = 0.037) but not cancer-free interval (P = 0.50). Similar to other well-known histomorphological features, KIT expression is a useful parameter of malignancy in cutaneous MCTs. KIT expression also predicted the biological behavior of the tumors in this study.

Hepatic fibrosis with bile duct ectasia and hyperplasia associated with polycystic kidney disease, analogous to Caroli syndrome in humans, was observed in a rat used as a control in a subchronic toxicity study. Light microscopy of liver sections showed multiple cystic and segmental saccular dilatations and hyperplasia of the intrahepatic bile ducts associated with overgrowth of portal connective tissue; the kidneys had diffuse cystic dilatation of cortical renal tubules. The lesions resembled those of human cases of the fibropolycystic disease termed as Caroli syndrome, which is thought to be the result of a pathologic developmental process known as ductal plate malformation. Recently, an animal model of Caroli syndrome has been described in mutant rats from a colony that constantly showed renal and hepatic cysts and an autosomal recessive mode of inheritance. The finding in our case of identical hepatorenal lesions suggests that the same mutation has occurred incidentally in a standard colony.