Jan 012000

Case of the month is our diagnostic challenge. We present cases seen by Cornell University’s Clinical Pathology Laboratory. These cover the gamut of venous blood smears, cytologic specimens and result (CBC, chemistry) interpretation, including those pesky erroneous results (usually due to preanalytical errors). A new case will be presented every month. Test yourself with the questions and photomicrographs and make your own diagnosis! The answer along with explanations and discussion is provided on the following page to see how close you came to the diagnosis.

We also have an index of our previous cases (with answers) if you wish to see a list of all the cases. Please note, that the search tool does not search case of the month (yet!).

Apr 012018

Tracheal wash from a goat


Case information

Fluid from a tracheal wash from three goats was submitted to the Animal Health Diagnostic Center for cytologic analysis, culture for aerobic bacteria and Mycoplasma species, and testing for small ruminant lentivirus. The herd was having a problem with chronic respiratory disease (no other information was provided). The submitted fluid was colorless and slightly cloudy (goat #1), colorless with flocculent material (goat #2) or light red and flocculent (goat #3). Direct and sediment smears were prepared from all fluids (no smears submitted), stained with modified Wright’s stain and examined. Images of the smears from two goats (#1 and #2) are shown below. Examine the images, then answer the provided questions.

  1. What cells can be identified in the fluid from the two goats? Similar cells were seen in the fluid from both goats (Figure 1 is from goat #1 and Figure 3 is from goat #2). 
  2. Is a cause for the chronic respiratory disease in the herd evident in the tracheal wash samples?


Figure 1: Tracheal wash (goat #1, 20x)


Figure 2: Tracheal wash (goat #2, 10x)


Figure 3: Tracheal wash (goat #2, 50x)


Answers on next page

Mar 112018

“Pulmonary mass” in a dog

Case Information

A 6 year old mixed breed dog presented for difficulty breathing. A single pulmonary mass was identified, and a fine-needle aspirate collected and submitted for cytological evaluation. CBC and biochemical panel results were unremarkable. Images of the aspirate are shown below:

Figure 1: Aspirate of pulmonary mass. Wright’s stain 4x.

Figure 2: Aspirate of pulmonary mass. Wright’s stain 50x.

Figure 3: Aspirate of pulmonary mass. Wright’s stain 50x.

Figure 4: Aspirate of pulmonary mass. Wright’s stain 50x.


1) What is the major cell type seen in this aspirate?
2) Take a close look at image 4, what second population of cells is evident?
3) How do you reconcile these findings with a lesion in the thoracic cavity?

Answers on next page

Feb 012018

Peripheral blood and pleural fluid from a dog

Case information

A 6.5 year old female spayed Cavalier King Charles Spaniel presented to the Cornell University Emergency Service for workup of an increased peripheral white blood cell count and pleural effusion detected by the primary veterinarian. Prior to presentation at Cornell, the primary veterinarian had removed approximately 300 mL of fluid from both sides of the chest. At presentation, the dog was quiet, alert, responsive, and tachypneic (44 bpm) with shallow breaths. Lung sounds were slightly decreased ventrally, compatible with an effusion. Thoracic radiographs confirmed a pleural effusion and revealed deviation of the trachea to the right with an enlarged mediastinal mass. The dog was placed into an oxygen cage due to low blood oxygen saturation (94%) on arterial blood-gas analysis and given intravenous fluid therapy at 1.5 times maintenance. Blood and pleural fluid were collected before treatment. Results are shown on the tables below.

Pertinent hematologic results
Test Result Units Reference interval
Hematocrit 40 % 41-58
Retic count 0.4 % 0.2-1.5
Absolute retic count 18.9 thou/μL 11.0-92.0
White blood cells 227.6 thou/μL 5.7-14.2
Seg neutrophils 4.6 thou/μL 2.7-9.4
Band neutrophils 2.3 thou/μL 0-0.1
Other leukocytes 211.7 thou/μL 0-0.1
Platelet count 108 thou/μL 186-545
MPV 17.5 fL 8.4-14.1
Mild toxic change in neutrophils


Pleural fluid 
Test Result Units
Volume 1.8 mL
Color Medium red
Turbidity Opaque
Total Protein (ref) <2.5 g/dL
Nucleated cells 16.0 thou/μL
Red blood cells 178.1 thou/μL



The “other cells” are shown on the representative photomicrographs of the blood and pleural fluid below. Based on the provided data, answer the following questions:

  1. What is the best interpretation for the leukocytosis?
  2. What additional diagnostic tests would you recommend for classification of the type of neoplasm? 

Figure 1. Peripheral blood from a dog. (Wright’s stain, 50x objective)

Figure 2. Peripheral blood from a dog. (Wright’s stain, 100x objective)

Figure 3. Pleural fluid from a dog. (Wright’s stain, 100x objective)

Answers on next page 

Jan 022018

Cerebrospinal fluid from a cat


Case information

A 10-year old-male castrated Domestic Shorthair cat presented to the Cornell University Hospital for Animals (CUHA) Emergency Service for a one-week history of collapsing episodes, as well as lethargy and decreased appetite of one month’s duration. Each episode occurred after the cat rose from bed and lasted 3-4 seconds, during which the cat would become stiff and fall down. The cat did not urinate or defecate during the episodes. No clinical signs were observed before or after the episodes. Based on the owner’s description and an unremarkable neurologic examination other than bilateral mydriasis, seizures were determined to be unlikely, and the cat was transferred to the Cardiology Service for a diagnostic work-up of presumed syncopal episodes.

An electrocardiogram (ECG) and echocardiogram were performed and unremarkable. The patient was sent home with a 24-hour Holter monitor, which recorded a brief period of mild bradycardia (100 bpm) during a collapse episode, however the heart rate was not considered low enough to cause syncope in a cat. No other significant arrhythmias or abnormalities were noted. Bloodwork abnormalities included a marked increase in creatine kinase (CK) activity (17,589 U/L, reference interval [RI], 73-388 U/L) and a moderately increased cardiac troponin concentration (1.39 ng/mL, RI 0.0-0.09 ng/mL). Both analytes were rechecked two days later; the CK activity had markedly decreased to 1,263 U/L and the troponin concentration had decreased, but was also still moderately elevated at 0.73 ng/mL. A consultation with the Neurology Service did not identify any major abnormalities, aside from bilateral mydriasis and possibly an abnormal gait in the pelvic limbs. The Ophthalmology Service performed a fundic examination and diagnosed bilateral chorioretinitis and posterior incipient cataracts.

The Internal Medicine Service was then consulted. Based on the increased CK activity and chorioretinitis, the leading differential diagnosis was toxoplasmosis. A serum sample was submitted for Toxoplasma gondii IgG and IgM antibody titers, and the cat was started on an empiric course of clindamycin. The episodes continued despite this treatment and titer results were negative for the presence of IgM antibodies. However, IgG antibodies were detected, suggesting previous exposure, but not an active infection.

The cat was presented again to the CUHA Neurology Service three weeks later. The neurologic exam was now markedly abnormal with an obtunded mentation, right head tilt, vestibular ataxia, decreased tactile placing in the left thoracic limb, and pain on palpation of the neck and head.  In addition, excessive sneezing was reported. Neurolocalization based on these signs diagnosed a left-sided paradoxical cerebellovestibular lesion. Bloodwork was unremarkable other than a persistently increased cardiac troponin concentration (0.64 ng/mL), but a repeat echocardiogram and electrocardiogram remained within normal limits. Magnetic resonance imaging (MRI) was then performed to further work-up the cat’s neurologic disease. Hyperintensity in the area of the cerebellum and midbrain was evident on T1-post contrast MRI, suggestive of infectious or inflammatory cerebellitis. An atlanto-occipital cerebrospinal fluid (CSF) tap was then performed and submitted for cytologic evaluation. The nucleated and red blood cell (RBC) counts of the CSF were 113 cells/μL and 3,714 cells/μL, respectively. The total protein was 29 mg/dL.

Evaluate the provided representative images and answer the following questions:

  1. How would you classify the inflammation?
  2. Can you identify the cause of the inflammation?
  3. What is the likely cause of the increased number of RBCs in the sample? 


Figure 1A: Cerebrospinal fluid from a cat (unstained, 50x objective)

Figure 2A: Cerebrospinal fluid from a cat (Wright’s stain, 50x objective)

Figure 3A: Cerebrospinal fluid from a cat (Wright’s stain, 100x objective)

Answer on next page

Dec 042017

Lymph node aspirate from a dog


Case Information

A 5-year old spayed female mixed breed dog (64 pounds) presented to the oncology service at Cornell University Hospital for Animals for further evaluation of a mass present for roughly one month on the ventral right side of the throat, alongside the trachea. On physical examination, the mass was approximately 7 cm in diameter, firm, and appeared deeply attached and not freely movable. A complete blood count, clinical chemistry profile, and urinalysis showed no significant abnormalities. A free T4 level ordered by the referring veterinarian was within normal limits. Thoracic radiographs and abdominal ultrasonography revealed no evidence of metastasis. However, a CT scan of the head and neck discovered right medial retropharyngeal lymphadenopathy (3.0 x 1.9 x 1.5 cm) in addition to the primary mass. Aspirates of the right medial retropharyngeal lymph node were submitted for cytologic evaluation.

Review the photomicrographs below and answer the following questions:

  1. Into which general tumor category would you classify the neoplasm (e.g epithelial, mesenchymal, round cell, endocrine/neuroendocrine)?
  2. Given the anatomic location of the primary mass, what are your top differentials?
  3. Does the unremarkable chemistry profile help rank your differentials?

Figure 1: Lymph node aspirate (20x objective)

Figure 2: Lymph node aspirate (100x objective)

Answers on next page 

Nov 012017

Liver imprint from a horse


Case information

An 11-month-old Thoroughbred filly presented to the Cornell University Hospital for Animals with a 10 day history of persistent lethargy, intermittent fever, diarrhea and hypodipsia. There was no response to antibiotics and fluids administered by the referring veterinarian.

On physical examination, the filly was quiet, alert and responsive, but in poor condition with a distended “pot-bellied” abdomen and dehydration. Mucous membranes of the oral and vaginal mucosa were hyperemic and the capillary refill time was 3 seconds. There were decreased borborygmi on abdominal auscultation. The filly had high heart and respiratory rates, with increased bronchovesicular sounds, and was afebrile.

Ultrasonographic examination of the thorax and abdomen revealed mild pleural roughening and a markedly enlarged liver that was comprised of several large or multiple coalescing masses, with intraluminal material in portal and splenic veins (suspected thrombosis). A 21 x 25 cm complex mass with a liquid center was noted in the cranial part of the abdomen. Thoracic radiographs did not reveal any abnormalities. Point-of-care testing revealed a packed cell volume of 64% and total protein by refractometer of 8.4 g/dL.

The filly was administered a bolus of 15 liters of intravenous fluids and then was treated with antibiotics and intravenous fluids overnight. The next day, blood was sampled for hematologic and biochemical testing (Tables 1 and 2) and a screening coagulation panel. Coagulation testing revealed a prolonged prothrombin time (27 seconds, reference interval 16-20 seconds) with a normal activated partial thromboplastin time (59 seconds, reference interval 45-66 seconds) and hyperfibrinogenemia (1131 mg/dL, reference interval 175-445 mg/dL). Bile acid testing revealed a high normal concentration (11 μmol/L, reference interval 0-11 μmol/L).

Table 1: Pertinent hematologic results
Test Result Units Reference interval
Hematocrit 51 % 31-47
MCV 33 fL 38-50
White blood cells 7.6 thou/μL 5.5-11.4
Neutrophils 4.6 thou/μL 2.7-6.6
Platelets 437 thou/μL 98-246
MPV 7.6 fL 5.8-11.5
Total protein by refractometer 8.9 g/dL 5.2-7.8


Table 2: Pertinent biochemical results
Test Result Units Reference interval
Sodium 129 mEq/L 134-141
Chloride 94 mEq/L 95-106
Bicarbonate 22 mEq/L 24-31
Anion gap 18 mEq/L 8-19
Albumin 2.1 g/dL 2.8-3.8
Globulin 5.7 g/dL 2.4-4.4
A/G 0.37   0.8-1.4
Glucose 52 mg/dL 75-117
AST 485 U/L 212-426
SDH 6 U/L 2-11
GGT 128 U/L 8-33
Total bilirubin 4.0 mg/dL 0.8-2.2
Direct bilirubin 0.5 mg/dL 0.1-0.3
Indirect bilirubin 3.5 mg/dL 0.5-2.1
CK 112 U/L 93-348
Iron 67 μg/dL 105-277
Transferrin saturation 21 % 26-62


The hepatic mass was biopsied under ultrasonographic guidance and scrapings were made from the submitted tissue, smeared onto slides and stained with modified Wright’s stain. Examine the representative images of the smears, then answer the questions below:

  1. Do most of the cells in the aspirate have features typical of mature hepatocytes?
  2. What is your cytologic diagnosis, incorporating all observed cytologic findings?
  3. Does this diagnosis provide pathophysiologic mechanisms that would explain some of the hematologic and biochemical findings?


Figure 1: Scraping from a liver mass (10x)


Figure 2: Scraping from a liver mass (50x).


Figure 3: Scraping from a liver mass (50x)


Figure 4: Scraping of a liver mass (50x)

Answers on next page

Oct 032017

Case Presentation

A 12 year old male, neutered domestic shorthair cat was presented to the Cornell University Hospital for Animals (CUHA) for an acute onset of paraplegia involving both distal limbs and difficulty breathing. The cat was up to date on all vaccinations. The complete biochemistry panel and blood gas results are shown below:

Biochemistry panel and blood gas results:

Chemistry Panel


 Blood gas results





  1. What major organ systems are affected in this cat and what do you think is the cause of the parapalegia?
  2. Describe and interpret the cat’s acid base status.
  3. What disease process is the cat at a major risk of developing (if he has not already)?

Answer on next page

Sep 012017

A Cat with a Renal Mass

Case Information

A 13-yr old female spayed domestic longhair cat presented to the oncology service at Cornell University Hospital for Animals for a renal tumor. The cat presented to the regular veterinarian with a 2-week history of progressive hyporexia, suspected weight loss and intermittent vomiting. On physical examination by regular veterinarian, the cat was noted to have bilateral renal enlargement, hypercalcemia and azotemia. At that time, renal neoplasia was discussed and supportive care was provided. Vomiting resolved with supportive care, but the cat continued to be progressively anorectic and continued to lose weight.

On presentation to Cornell, the cat’s temperature, respiration and heart rate were within normal limits. The cat was quiet, but alert and responsive, with a body condition score of 3/9 (cachectic). On abdominal palpation the right and left kidneys were moderately and mildly enlarged, respectively. A complete blood count revealed a mild normocytic normochromic non-regenerative anemia (RBC 6.5 mill/uL [reference interval 6.9-10.1 mill/uL]; MCV 48 fL [reference interval 40 – 52 fL]; MCHC 33 g/dL [reference interval 32 – 35 g/dL]), consistent with anemia of chronic disease, and a moderate thrombocytopenia (92 thou/uL [reference interval 195-624 thou/uL]). Serum biochemical testing revealed a moderate azotemia (urea nitrogen 74 mg/dL [reference interval 16 – 36 mg/dL]; creatinine 1.8 mg/dL [reference interval 0.6 – 2.0 mg/dL]) interpreted as a renal azotemia, moderate hypercalcemia (16.4 mg/dL [reference interval 9.1-10.9 mg/dL]) with a moderate increase in ionized calcium (2.25 mmol/L [reference interval 1.11-1.38 mmol/L] with a concurrent mild hypophosphatemia (2.6 mg/dL [reference interval 2.7-6.2 mg/dL]), mild proportional hyponatremia and hypochloremia (sodium 150 mEq/L [reference interval 151 – 158 mEq/L]; chloride 112 mEq/L [reference interval 113 – 123 mEq/L]), interpreted as fluid losses (likely renal) with water replenishment through drinking. There was mild evidence of muscle injury (creatine kinase 735 U/L [reference interval 73 – 388 U/L] and AST 65 U/L [reference interval 15 – 44 U/L]). Concurrent liver injury could not be ruled out, particularly as the cat had very mildly alkaline phosphatase activity (85 U/L [reference interval 13 – 83 U/L]).

Abdominal ultrasound revealed a mass in the right kidney and extending into renal vessels, that was lobulated and heterogeneous. A fine needle aspirate of the mass was performed. Evaluate the photomicrographs of the fine needle aspirate and answer the following questions:

Figure 1A: Fine needle aspirate of a renal mass (Wrights stain 20x)

Figure 1B: Fine needle aspirate of a renal mass (Wright’s stain 20x)

Figure 1C: Fine needle aspirate of a renal mass (Wright’s stain 50x)

  1. What uncommon findings are present in the fine needle aspirate of the renal mass?
  2. How would the hypercalcemia be explained in this case?

Answer on next page

Aug 012017

Peritoneal fluid from a horse

Case information

A 5 year old Thoroughbred-paint gelding presented to the Cornell University Large Animal Hospital with a history of increased respiratory effort, abdominal distention, and depression after turn out to a new pasture. On presentation, the horse was quiet, alert and responsive, and vital signs were within normal limits. Physical examination revealed abdominal distention and pain, decreased intestinal sounds, and abnormal rectal palpation (absence of fecal material, distended cecum, and dilated loops of small intestine). Due to the marked abdominal distention, the cecum was trocharized and some of the gas distention was relieved. The horse was treated with intravenous fluids and 2% lidocaine (250 mL as a constant rate infusion) for pain control and monitored overnight. The day after initial presentation, the horse’s condition had improved and rectal examination revealed normal formed manure and decreased colon distention. The lidocaine infusion was discontinued. On the second day of hospitalization, blood and peritoneal fluid were collected and submitted for a complete blood count and biochemical analysis, and cytologic evaluation, respectively.

Blood work revealed  a mild non-regenerative anemia with a hematocrit of 32% (reference interval [RI], 34-46%) interpreted as decreased erythropoiesis in response to inflammation. There was an inflammatory leukogram due to the presence of a mild left shift (0.3 thousand/µL; RI, 0.0-0.1 thousand/µL), and mild toxic change, despite normal total leukocyte (5.5 thousand/µL; RI, 5.2-10.1 thousand/µL) and neutrophil (4.6 thousand/µL; RI, 2.4-6.6 thousand/µL) counts. There was a mild lymphopenia of 0.6 thousand/µL (RI, 1.2-4.9 thousand/µL) supporting concurrent stress (glucocorticoid response). Biochemical results were overall unremarkable.

The submitted peritoneal fluid was light-orange in color and opaque, with a total protein by refractometry of 5.5 g/dL (upper reference limit, <2.5 g/dL). The total nucleated cell count was 1004.6 thousand/µL (RI, <5.0 thousand/µL) and the red blood cell count was 314.2 thousand/µL. Direct smears from the submitted fluid were prepared and examined.

Evaluate the representative photomicrographs of the peritoneal fluid shown below and answer the following questions:

  1.  Identify the cells labeled as “A” and “B” in Figure 3.
  2.  How would you classify the effusion? Can you identify a cause?
  3. What do you think the prognosis would be for this horse?


Figure 1. Peritoneal fluid from a horse (Wright’s stain, 20x objective)


Figure 2. Peritoneal fluid from a horse (Wright’s stain, 50x objective)


Figure 3. Peritoneal fluid from a horse (Wright’s stain, 100x objective)


Figure 4. Peritoneal fluid from a horse (Wright’s stain, 100x objective)

 Answers on next page

Jul 012017

Laboratory data from a jaundiced dog

Case presentation

A 9 year-old female spayed Pomeranian was presented to the Cornell University Hospital for Animals (CUHA) Emergency Service as a referral for markedly increased liver enzymes and cholesterol. The dog presented to the referring veterinarian with a two day history of vomiting, constipation, inappetence, and lethargy. After two days of medical therapy with no improvement, the dog was referred for further diagnostic testing and treatment.

Upon presentation to CUHA, the dog was bright, alert, responsive, and anxious.  Vital signs (temperature, pulse, and respiratory rate) were within normal limits. On physical examination, the dog was uncomfortable on abdominal palpation and the liver was palpably enlarged.  Jaundice of the skin and sclera OU were also observed.  The only other physical examination abnormality was a grade 1/4 luxating right patella.  Blood was collected for a complete blood count (CBC) and serum chemistry panel; relevant results of which are presented below. Evaluate the provided results and answer the questions posed below:

Table 1: Complete hemogram, EDTA
Test Result Reference interval Unit
WBC 15.7 5.7-14.2 thou/ul
Segmented neutrophils 13.0 2.7-9.4 thou/ul
Band neutrophils 0.0 0.0-0.1 thou/ul
Lymphocytes 0.5 0.9-4.7 thou/ul
Monocytes 2.0 0.1-1.3 thou/ul
TP-ref 9.0 5.9-7.8 g/dL
RBC morphology Moderate rouleaux formation
Plasma appearance Marked icterus


Table 2:  Chemistry, serum
Test Result Reference interval Unit
Total protein 5.2 5.3-7.0 g/dL
Albumin 2.8 3.1-4.2 g/dL
Globulin 2.4 1.9-3.6 g/dL
Glucose 142 63-118 mg/dL
ALT 2698 20-98 U/L
AST 564 14-51 U/L
Alkaline phosphatase 3590 17-111 U/L
GGT 309 0-6 U/L
Total bilirubin 16.3 0.0-0.2 mg/dL
Direct bilirubin 14.1 0.0-0.1 mg/dL
Indirect bilirubin 2.2 0.0-0.2 mg/dL
Cholesterol 782 138-332 mg/dL
Creatine kinase 1478 48-261 U/L
Iron 261 78-214 ug/dL
Transferrin saturation 77  23-61 %


  1. What does rouleaux formation of red blood cells (RBCs) indicate? 
  2. What are three explanations for the marked discrepancy between the total protein result on the CBC and chemistry panel in this case? Which result do you think is a better reflection of the patient’s total protein concentration?
  3. What pathologic processes can be identified based on the provided chemistry results? What are your differential diagnoses and what diagnostic test would you recommend?

Answers on next page