MALAKOPLAKIA, A RARE INFLAMMATORY CONDITION, IN A SUBLUMBAR MASS OF A 6 YEAR OLD CAT

PATIENT INFORMATION:

SPECIES/BREED: Feline/Domestic Short Hair

AGE: 6 years old

GENDER: MN

WEIGHT: 14 lbs

HISTORY:

The patient was presented for decreased appetite, lethargy, and occasional vomiting. The owner also reported diarrhea and leaking liquid feces. The patient has a chronic history of allergic dermatitis and otitis, which had been treated with oral cyclosporine for several months.

RADIOGRAPHS:

ABDOMINAL ULTRASOUND FINDINGS:

The bladder is moderately distended and turgid containing a moderate amount of echogenic luminal debris.

In the caudal abdomen dorsal to the bladder and colon is a very large (at least 3.5 x 4.8 trans, 3.2 x 5.6 sag) heterogenous hypoechoic mass which extends into the pelvic canal. Color flow is mild with Doppler color exam. Ultrasound guided fine needle aspirates were obtained.

CYTOLOGY FINDINGS:

Microscopic Description The slides are moderately to highly cellular and consist of a small to moderate amount of cellular debris, a proteinaceous background, few red blood cells and a nucleated cell population predominated by nondegenerate neutrophils with fewer but numerous macrophages that frequently exhibit leukophagocytosis. No microorganisms found after thorough search.

CYTOLOGIC DIAGNOSIS:

Most consistent with pyogranulomatous inflammation

Casey J. LeBlanc DVM, PhD, Diplomate, ACVP (Clinical Pathology)
Eastern VetPath

ADDITIONAL DIAGNOSTICS:

Auburn University Feline Infectious Peritonitis Virus mRNA: NEGATIVE

CT Scan:

There is a heterogenous soft tissue attenuating, variably contrast-enhancing mass extending through the pelvic canal into the caudal abdomen. The mass is causing significant cranial displacement of the urinary bladder. The mass is approximately 9-10 cm in sagittal length and 3-4 cm in cross-sectional height/width. The mass fills the entire cross-sectional diameter of the pelvic canal and appears to be causing severe ventral displacement of the colon, rectum and visible urethra. Mass margins are not well-defined relative to the hypaxial musculature ventral to the caudal lumbar, sacral and cranial coccygeal vertebrae.

Alaina Carr DVM, DACVR
Seattle Veterinary Specialists-Kirkland

Although it was unsure based on CT if complete excision could be achieved, the owners elected to attempt surgery because of the the cat’s increasing level of discomfort. Dysuria had been noted as well as tenesmus. The majority of the mass was removed and submitted for histopathology.

SURGERY REPORT:

A mass in the pelvic region just to the right of midline was carefully dissected from the right ureter and the iliac vessels. The mass was mildly friable and the surface vaguely appeared like the capsule of a lymph node. It was approximately 9 cm X 6 cm X 4 cm. The mass dove into epaxial muscle region. The mass was debunked removing at least 90% of what was present visibly and with palpation. The pelvic canal seemed to be free of obstruction.

HISTOPATHOLOGY FINDINGS:

Microscopic Findings: Sublumbar mass: Severe, dense, histiocytic inflammation consistent with malakoplakia.

COMMENTS FROM THE PATHOLOGIST:

Malakoplakia is a rare, reactive/inflammatory lesion most often associated with the presence of E. coli. It is caused by alterations in the degradative functions of macrophages following phagocytosis of bacteria (usually E. coli or Proteus) which results in a chronic inflammatory lesion that usually requires surgical excision for resolution. Since this disease is so rare, the diagnosis is somewhat presumptive and other well differentiated proliferations of histiocytes (such as a well-differentiated histiocytic sarcoma or a histiocytic proliferative disorder such as dendritic cell histiocytosis) were considered but are not favored.

Amy M. Boker, VMD, Diplomate ACVP
Antech

FOLLOW UP:

Malakoplakia is a rare condition in animals as well as humans. It is usually associated with the bladder, however, in this case, it was localized in the sub lumbar lymph node. It is a granulomatous disease characterized by impaired histiocytes that incompletely phagocytize bacteria, causing accumulation in macrophages.

This patient is doing very well after surgery with no other treatment required. The use of cyclosporine has been discontinued as this condition can sometimes be associated with immunosuppression.

Thank you to Drs. Watson and Sparkman at Noah’s Ark Veterinary Hospital for updates on this interesting case, as well as to Eastern VetPath, Antech, and Blue Pearl for the additional diagnostics!