Patient Information:

Age: 11 years

Gender: Spayed Female

Breed: Himalayan

Species: Feline

History:

Patient presented with a history of diarrhea and significant weight loss. Laboratory work revealed a severe neutrophilic leukocytosis, non-regenerative anemia and hypoalbuminemia.

Abdominal Ultrasonographic Findings:

The aboral ileum and oral ascending colon are severely thickened (up to 7.2mm) and hypoechoic with complete loss of normal layering distinction creating a mass effect of 3.5x2.5cm at the ileocecocolic junction.

Prominent (1.0cm diameter) rounded hypoechoic mesenteric lymph nodes are noted in the area of the ICCJ mass.

A scant amount of anechoic peritoneal fluid is present.

The mesentery is moderately-severely hyperechoic surrounding the ICCJ mass.

A homogenous rounded hypoechoic mass (1.2x1.1cm) is present that appears to originate from the peritoneal wall and extends into the peritoneal cavity.

Ultrasound Interpretation:

Ileocecocolic Mass - the findings are severe - DDx: adenocarcinoma vs. infiltrative neoplasia (lymphosarcoma vs. mast cell tumor) vs. feline gastrointestinal eosinophilic sclerosing fibroplasia (FGESF) vs. leiomyosarcoma vs. leiomyoma.
Lymph nodes - the findings are moderate - DDx: reactive vs. infection vs. infiltrative neoplasia (lymphoma vs. mast cell vs. other) vs. metastatic neoplasia
Body wall mass-the findings are moderate-DDX: metastasis (carcinomatosis) vs granuloma vs other
Ascites- this finding is very mild - DDx: transudate vs. hemorrhagic vs. exudate

Diagnostic Recommendations:

While disseminated disease was suspected, ultrasound guided fine needle aspirate was recommended in an attempt to arrive at a more definitive diagnosis.

Cytology Results:

Diagnosis
ICCJ Mass: Suspect carcinoma
Body Wall mass: Suspect carcinoma

Comments
For both locations, a carcinoma is suspected with 80% confidence, suggestive of a metastatic process. However, due to a lack of convincing criteria of malignancy, aspiration of two benign epithelial proliferations cannot be completely ruled out. Consider biopsy/histopathologic evaluation.

Microscopic description
The slides from the two locations appear very similar, are moderately cellular, and consist of a small amount of cellular debris, few to many red blood cells and a nucleated cell population predominated by mature leukocytes in proportions consistent with the peripheral blood present, with fewer round to polygonal cells found in cohesive clusters. These cells have a small amount of very basophilic cytoplasm that surrounds a central, round nucleus with a coarsely-stippled chromatin pattern and occasional visible nucleoli. Anisokaryosis is mild to moderate.

Casey J. LeBlanc, DVM, PhD, DACVP (Clinical Pathology)

Recommendations:

Carcinomatosis was the most likely diagnosis given the full clinical picture. Oncology consult was recommended for optimal diagnostic and treatment plan vs palliative care vs humane euthanasia. Prognosis was very guarded given current information.

Patient outcome:

Palliative care was initially elected, but due to continued declining condition, the owner elected humane euthanasia a short time later.

Discussion:

Carcinomatosis is the widespread dissemination of tumor cells in a body cavity (often peritoneal). This is most often from an epithelial cell tumor, but can also occur with sarcoma or lymphoma. The most common primary tumor sites are pancreas, gastrointestinal tract and hepatobiliary system. It is also important to note that a primary tumor is not always identified. Ascites of varying echogenicity is typically present as well as hypoechoic nodules within the mesentery. In some cases, such as this one, nodules can occur on the body wall. Lymphadenopathy is also common.

Diagnosis can be challenging; biopsy and histopathology may be needed for definitive diagnosis. However, as in this case, less invasive ultrasound guided fine needle aspirates can sometimes yield results and should be discussed when the suspicion of carcinomatosis is present.

Unfortunately, limited treatment options exist for carcinomatosis and the treatment is often palliative involving periodic abdominocentesis to relieve discomfort, anti-nausea medication and pain control as this condition is often described as painful in humans. Intracavitary carboplatin has been attempted, but no studies have demonstrated efficacy in cats and it remains only a palliative option at this time.

References:

Monteiro CB, O’Brien RT. A retrospective study on the sonographic findings of abdominal carcinomatosis in 14 cats. Vet Radiol Ultrasound 2004; 45: 559–564l; Weston PJ, Baines SJ, Finotello R, et al.

Clinical, CT, and ultrasonographic features of canine and feline pleural and peritoneal carcinomatosis and sarcomatosis. Vet Radiol Ultrasound 2021; 62: 331–341.