Feline Plasma Cell Tumor in Multiple Locations

Patient Information

Age: 12 years

Gender: Castrated Male

Breed: Domestic Medium Hair cat

Weight: 11 pounds

History

Presented for abdominal ultrasound to evaluate for underlying cause of anorexia, lethargy, weight loss and recent history of diarrhea. A firm grape sized nodule was also noted on the top of the patient’s head.

Abdominal ultrasound findings

Kidneys: Both kidneys have normal size (Lt/Rt = 3.5/3.6cm ) and normal shape with coarse mild to moderately hyperechoic renal cortices which are disproportionately large. There is mild loss of the corticomedullary junction distinction. No pyelectasia seen. There is a small (0.3x0.4cm) hypoechoic homogenous nodule in the left kidney.

Spleen: Mildly enlarged (1.3cm depth) with mildly rounded shape and normal echogenicity. No focal lesions appreciated.

Bladder: The bladder is moderately distended with anechoic urine and is of relatively normal contour and thickness. There is a small 0.3x0.2cm bladder wall nodule in the right mid-caudal bladder.

Gastrointestinal Tract

The stomach is empty and collapsed with normal rugal folds and layering.
Many loops of intestine are prominent and mildly to moderately thickened (Duodenum 3.1mm; Jejunum 2.6-3.1 mm (normal wall thickness ~2.2-2.5mm, > 2.8mm abnormal Norsworthy/Estep et. al. JAVMA, Vol 243, No. 10, November 15, 2013)). Some have abnormal layering with prominent disproportionate thickening of the muscularis layer.
The colon is mildly thickened (2.0mm) and has normal layering throughout.

Differentials Splenomegaly: the findings are mild DDx. neoplasia (mast cell, lymphoma, carcinoma, metastatic disease) vs. fungal (Histoplasmosis) vs. reactive lymphoid hyperplasia vs. splenitis vs. congestion vs. extramedullary hematopoiesis (EMH).

Intestines: the findings are mild DDx. inflammatory bowel disease/food intolerance vs. infiltrative neoplasia (small-cell lymphosarcoma vs. mast cell tumor) vs. parasitism (cestode) vs. dry FIP vs. fungal (histoplasmosis). Inflammatory bowel disease in cats can be chronic and long-standing but in many cases will transition into small-cell lymphosarcoma and it is not possible with ultrasound alone to determine in this case whether the disease is benign or infiltrative.

Inflammation of Large Intestine: the findings are mild DDx. Acute colitis/proctitis vs. Chronic colitis (Lymphocytic/plasmacytic colitis vs. Eosinophilic enterocolitis vs. Chronic ulcerative colitis) vs. IBS

Bladder Nodule: the findings are mild DDx. Tumors of the urinary bladder are uncommon in dogs and rare in cats. Transitional cell carcinoma (TCC) is the most common primary tumor of the urinary bladder in both species. Other differentials include squamous cell carcinoma, leiomyosarcoma, leiomyoma, and rhabdomyosarcoma or benign bladder polyp. The bladder may also be invaded by prostatic neoplasia or metastatic disease (e.g., hemangiosarcoma, lymphoma). Bacterial cystitis and urolithiasis are common differentials for the clinical signs seen, and a rare but important differential diagnosis for mass lesions is benign polyps of the urinary bladder.

Additional Diagnostics

Ultrasound guided fine needle aspirates of the spleen were obtained for cytology. A fine needle aspirate of the nodule on the head was also performed. Samples of both sites were submitted to Eastern Vet Path for analysis.

Cytology Microscopic Description

Nodule on top of head: The slides are lightly to highly cellular and consist of few to many red blood cells and a nucleated cell population predominated by individual round cells with very low numbers of neutrophils and small lymphocytes. These round cells have a moderate amount of basophilic cytoplasm, and occasional prominent perinuclear clear area, and eccentric, round two lobulated nuclei. The nuclei have a densely clumped chromatin pattern. Anisokaryosis is mild; bi nucleation is rarely noted. Occasional mitotic figures are present. See photo below.

Spleen: the slides are of low to high cellularity with few to several red blood cells. Large round cells that resemble those found in the nodule predominate. Few small lymphocytes, occasional neutrophils and rare macrophages are also present.

COMMENTS

For both locations, cytologic findings are consistent with a plasma cell tumor, 90-100% confidence. If not already performed, consider measuring globulin concentration ± SPE. Screening the liver and bone marrow may also be considered

Diagnosis

Nodule on top of head: Plasma cell tumor
Spleen: Plasma cell tumor

Discussion

Unexpectedly, both fine needle aspirates revealed the same disease, plasma cell tumor, suggesting metastatic disease and/or multiple myeloma.This patient was sedated, so splenomegaly could have been secondary to sedative medications. The nodule on the head had many other differentials as well. Aspiration of abnormal findings can often yield rewarding diagnostic results even when unexpected.

Outcome

Additional diagnostics to consider for this patient would include measuring globulin concentration ± serum protein electrophoresis. Screening the liver and bone marrow may also be considered. Referral for oncology consultation and a recheck sonogram to monitor the nodule in the kidney and in the bladder was also recommended. Unfortunately, this patient was humanely euthanized due to poor clinical condition and diagnosis of neoplasia