Malignant transformation and subsequent leptomeningeal carcinomatosis of a gastric polyp in a dog.

Progressive carcinogenesis of a gastric polyp with transformation to gastric adenocarcinoma and subsequent development of leptomeningeal carcinomatosis is described in an adult male Scottish terrier. Presenting clinical signs consisted of vomiting with intermittent hematemesis. Surgical biopsies over the course of 14 months documented the progression from gastric polyp to minimally invasive gastric carcinoma to invasive gastric adenocarcinoma, a pathogenesis not previously documented in veterinary oncology. The patient ultimately developed neurologic pathology and was euthanized, and necropsy evaluation identified widespread carcinomatosis with accompanying leptomeningeal metastasis. As in humans, gastric polyps in dogs rarely have malignant potential.

Detection of Leptomeningeal Carcinomatosis by Cerebrospinal Fluid in a Dog with a Negative MRI.

An 11 yr old female French bulldog was presented for acute onset of seizures and a 2 wk history of disorientation. On physical examination, a nodular mass at the fourth mammary gland level was observed. Neurological evaluation showed obtundation and compulsive behavior. Brain MRI study did not reveal any abnormalities. Cerebrospinal fluid (CSF) collected from the cerebellomedullary cistern showed a marked increase of total nucleated cell count (400 cells/µL). Cytological evaluation identified the presence of a monomorphic round cell population characterized by large cell bodies, a single eccentrical located nucleus with high nuclear:cytoplasmatic ratio, and marked atypia with anisocytosis, anisokaryosis, and multiple nucleoli. Leptomeningeal carcinomatosis (LC) was suspected. The dog was euthanatized for worsening of clinical signs. Post-mortem examination identified an anaplastic mammary carcinoma in the nodular mammary mass. Infiltration by neoplastic cells exhibiting the same morphological features was detected along leptomeninges of the telencephalon and cerebellum associated with cortical and subcortical parenchymal micrometastases. To our knowledge, this is the first case of LC in a dog detected by CSF evaluation but without any MRI abnormalities. This finding emphasizes the usefulness of CSF cytology in patients with suspected LC even in the absence of any MRI identifiable lesions.

Meningeal carcinomatosis in a dog: magnetic resonance imaging features and pathological correlation.

A six-year-old cross breed dog was presented with a four-month history of seizure activity, which was unresponsive to anticonvulsive therapy and an acute deterioration in neurological status, evident as central blindness. Cyst-like structures and nodular enhancement within the subarachnoid space were shown on a magnetic resonance image (MRI) scan. Histopathological examination of brain tissue was consistent with meningeal carcinomatosis.

Neoplastic pleocytosis in a dog with metastatic mammary carcinoma and meningeal carcinomatosis.

A 12-year-old female spayed Labrador Retriever was presented with a history of seizures and abnormal vocalization. Approximately 1 year before presentation, multiple mammary cysts had been surgically excised. A mammary mass was noted on physical examination, and 2 separate parenchymal brain lesions were found on imaging studies. Cerebrospinal fluid (CSF) collected from the cisterna magna was analyzed, and abnormalities included moderate pleocytosis with atypical discrete round cells that occasionally formed loose clusters. The dog was euthanized, and on necropsy a primary solid mammary carcinoma was identified as well as multiple metastatic foci in the brain with diffuse meningeal involvement. The cells in the CSF had a morphologic appearance similar to the cells in the primary mammary tumor and in the metastatic tumors in the brain. On immunostaining, cells from the primary mammary tumor, the brain tumors, and the CSF expressed cytokeratin. The CSF cells did not express CD18, CD3, or CD79a. A final diagnosis of mammary carcinoma with brain metastasis and meningeal carcinomatosis was made.