Jan 012000

In our diagnostic challenges, 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 4-6 times a year. 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 the diagnostic challenges (yet!).


*NEW 2022*


In collaboration with Scopio, our diagnostic challenges, when possible, will be available as digital slides. So feel free to look at the actual slide used with the case (when available) in the gallery (Mac and PC friendly!).

Dec 202021

Aspirate from the gall bladder of a cat

Case Information

An 11-year-old female spayed domestic shorthair cat was presented with a 3-4 week history of progressive weight loss. The cat was obtained as a kitten from the island of St John and then had lived on a farm in Massachusetts until 8 years of age. The cat had been solely an indoor cat for the prior 3 years with the current owner.  

On examination, the cat was quiet, alert, and responsive, but febrile (102ºF) and tachycardic (200 beats per minute), with slight tachypnea (32 breaths per minute). The rest of the physical examination was within normal limits. Clinical pathology testing revealed normal hemogram results with several abnormalities in a biochemical panel, including hyperglycemia (298 mg/dL, reference interval [RI], 71-182 mg/dL), increased alanine aminotransferase (ALT) (432 U/L, RI, 28-109 U/L), alkaline phosphatase (ALP) (424 U/L, RI, 11-49 U/L), γ-glutamyl transferase (GGT) (10 U/L, RI, 0-2 U/L) activities, and increased total bilirubin concentration (1.6 mg/dL, RI, 0-0.2 mg/dL). Urine dipstick analysis revealed a 2+ reaction for glucose, 3+ reaction for ketones, and 2+ reaction for bilirubin. Abdominal ultrasonography revealed a mildly enlarged liver that was moderately hyperechoic, a full gall bladder with anechoic bile, and a dilated common bile duct. The liver and gall bladder were aspirated and submitted for cytologic evaluation. View the representative photomicrographs of the direct smear of the aspirated bile and answer the questions below. 

  • Based on the provided imaging findings and biochemical results, what disease process(es) is/are occurring in the liver, i.e. what do you expect to see in the liver aspirate?
  • Can you think of a contributing cause?
  • What biochemical result is unexpected for the suspected pathologic process involving the liver?
  • What is your cytologic diagnosis from the bile?
  • Do the findings in the bile explain the changes in the biochemical panel?

Figure 1: Gall bladder aspirate from a cat (10x objective)

Figure 2: Gall bladder aspirate from a cat (60x objective)


Answers on next page

Nov 012021

Aspirate from a mandibular mass in a cat

Case Information

A mature male domestic shorthair cat was presented to Cornell University Hospital for Animals with an ulcerated, non-healing cutaneous and subcutaneous mass over the left mandible close the chin. The left submandibular lymph node was also noted to be moderately enlarged on physical examination. A fine needle aspirate was performed on the mandibular mass and representative figures of a direct smear are shown below. After viewing the images, answer the questions below.

  1. What differential diagnoses should be considered for the left mandibular swelling in this cat?
  2. What is your interpretation based on the cytologic findings?

Figure 1: Mandibular mass aspirate in a cat (20x objective, Wright’s stain)

Figure 2: Mandibular mass aspirate in a cat (50x objective, Wright’s stain)


Answers on next page

Sep 052021

Laboratory data from an acutely collapsed dog

Case Information

A 1-year-old spayed female Maltese-cross dog was presented as an emergency to Cornell University Hospital for Animals for acute collapse. The dog had been healthy up until this acute event, which happened suddenly during routine play outdoors. On physical examination, the dog was depressed and hypothermic, tachycardic (250 beats per minute) and tachypneic (78 breaths per minute). Systolic blood pressure was low (96 mmHg systolic/68 mmHg diastolic; reported mean ± standard deviation, 120 ± 19 mmHg systolic and 67 ± 14 mmHg diastolic via oscillometric methods1). The dog was painful on abdominal palpation and had profuse bloody diarrhea. A focused assessment with sonography in trauma (FAST) scan of the abdomen revealed a moderate amount of ascites and edema in the mesentery (hyperechoic), gall bladder wall (thickened wall with hyperechoic and hypo-echoic inner and outer walls, respectively), small intestine (diffusely thick and hyperechoic), and pancreas (thicker than normal with anechoic strands). The sonographic results were compatible with edema in multiple organs. 

Results of quick assessment tests showed a packed cell volume (PCV) of 52% (reference interval [RI], 42-54%), total solid concentration of 5 g/dL (RI, 5.9-7.8 g/dL), glucose of 359 mg/dL and urea nitrogen of 15-26 mg/dL. A venous blood gas analysis yielded a pH of 7.43 units (RI, 7.32-7.38 units), with a pCO2 of 28 mmHg (RI, 38-46 mmHg), bicarbonate of 18 mmol/L (RI, 20-25 mmol/L) and base excess of -7 mmol/L (RI, -6 to 0 mmol/L). Sodium and chloride concentrations were 149 (RI, 145-151 mEq/L) and 115 (RI, 110-119 mEq/L) mEq/L, respectively. The pO2 was 45 mmHg (RI, 45-67 mmHg). The lactate concentration was 1.7 mmol/L (normal <2.0 mmol/L; measured 15 minutes after the blood gas analysis). 

The dog was treated symptomatically with intravenous fluids, anti-emetics, pain relief and antibiotics overnight and blood was taken for a hemogram, coagulation panel, and biochemical profile the next morning. Results are shown below, along with four questions related to the results.

  1. What is your interpretation of the point-of-care blood gas results?
  2. Considering the quick assessment tests, how would you interpret the changes in analytes in the hemogram and biochemical profile?
  3. What pathologic processes are revealed by the clinical pathologic results?
  4. What is your top differential diagnosis?


Answers on next page

Jul 182021

Pleural fluid from a young goat

Case Information

A 9 month old male Billy goat presented to the Cornell Equine & Nemo Farm Animal Medicine Service vocalizing and in respiratory distress. On presentation, the patient was tachycardic (220 beats per minute), vocalizing, and had pale mucous membranes. Point-of-care bloodwork revealed a severe anemia (packed cell volume, 14%), mild to moderate hypoproteinemia (5.8 mg/dL, reference interval (RI): 6.2-8.0 mg/dL), moderate azotemia (blood urea nitrogen 45 mg/dL, RI: 11-27 mg/dL; creatinine 2.1 mg/dL, RI: 0.4-2.2 mg/dL), and a high normal pH with a markedly increased anion gap (29 mmol/L, RI: 5-15 mmol/dL) and evidence of a mixed acid-base disturbance (primary respiratory alkalosis and primary titration metabolic acidosis, with the latter likely due to severe hyperlactatemia [18.6 mmol/L, RI: 0.3-1.5 mmol/L]). A point-of-care CBC revealed a moderate leukocytosis (32.7 x 103/µL, RI: 7.2-17.7 x 103/µL) consisting of a marked neutrophilia (23.5 x 103/µL, RI: 1.9-9.5 x 103/µL) and a moderate monocytosis (2.1 x 103/µL, RI: 0.0-0.9 x 103/µL).

Thoracic ultrasonographic examination was performed, which revealed a left-sided pneumothorax, a moderate amount of free fluid in the cranioventral thorax, and abnormal lung parenchyma. A chest tube was placed in the left side of the thorax and 240mL of air was removed for stabilization purposes. Overnight treatment included flow-by oxygen, intravenous (IV) fluid therapy, and administration of antibiotics and pain medication as well as nebulization with albuterol and N-acetylcysteine.

Repeat blood testing was performed the next day, which still showed a marked anemia (hematocrit 11%, RI: 28-44%) with no evidence of regeneration on smear examination, improving inflammation (segmented neutrophil count 16.0 x 103/µL, RI: 1.9-9.5 x 103/µL, band neutrophil count 0.4 x 103/µL, RI: 0-0.1 x 103/µL, with mild toxic change), mild thrombocytopenia (204 x 103/µL, RI: 247-912 x 103/µL), persistent mild azotemia (urea nitrogen 55 mg/dL, RI: 10-35 mg/dL; creatinine 1.3 mg/dL, RI: 0.3-0.8 mg/dL), and marked hepatocellular injury (AST 2014 U/L, RI: 62-145 U/L; SDH 1700 U/L, RI: 24-63 U/L; GLDH 1150 U/L, No RI) with a mild increase in total and direct bilirubin (total bilirubin 0.3 mg/dL, RI: 0-0.2 mg/dL; direct bilirubin 0.2 mg/dL, RI: 0.0 mg/dL) concentrations. Increased GGT activity (118 U/L, RI: 24-64 U/L) could be attributed to cholestasis, biliary hyperplasia or biliary epithelial necrosis. Total protein and albumin concentrations were decreased (total protein 6.0 g/dL, RI: 6.2-8.0 g/dL; albumin 2.5 g/dL, RI: 2.9-4.0 g/dL), but globulin concentrations were within low normal limits.

A blood transfusion was administered and a thoracocentesis was performed. The collected pleural fluid was submitted to the clinical pathology laboratory for analysis. Results and images from the pleural fluid analysis are provided below. 

Examine the representative images of the smears or view the digital slide (#2087) in the eClinPath Scopio Gallery and answer the questions below. Note that the scanned slide is quite thick, so the best area to identify the cells is at the leading edge, which is the thinnest area.

  1. Considering the predominant leukocyte in the fluid, what is your top differential diagnosis for this patient?
  2. What other process is occurring based on the appearance of the macrophages in the figures?

Figure 1: Pleural fluid from a goat (Wright’s, 50x objective)

Figure 2: Pleural fluid from a goat (Wright’s, 100x objective)


Answers on next page

Apr 272021

Aspirate of a retrobulbar mass in a dog

Case Information

A 6-year-old male neutered mixed breed dog was presented to the Ophthalmology Service at Cornell University for evaluation of an optic nerve tumor in the right eye. Approximately one year prior, the patient had developed a raised third eyelid and exophthalmos in the right eye, which ultimately progressed to vision loss. On physical examination, the patient’s right eye was exophthalmic with scleral injection. The pupillary light reflex and menace response were absent. Upon fundic examination, retinal detachment and increased size of the optic nerve were noted. A computerized tomography (CT) scan of the skull revealed a large retrobulbar mass with intraocular and intracranial extension and a separate discrete intracranial nodule. Fine needle aspirates were taken from the retrobulbar mass for cytologic examination.

Examine the representative images of the smears or view the digital slide in the eClinPath Scopio Gallery and answer the questions below:

  1. Based on the location, pattern of cell arrangement and shape of the cells, what is your primary differential diagnosis?
  2. What additional tests can be performed to confirm your diagnosis?

Figure 1: Right retrobulbar mass (Wright’s stain, 10x objective)

Figure 2: Right retrobulbar mass (Wright’s stain, 50x objective)

Figure 3: Right retrobulbar mass (Wright’s stain, 50x objective)

Figure 4: Right retrobulbar mass (Wright’s stain, 100x objective)


Answers on next page

Feb 012021

Tracheal wash from a Malayan tiger (Panthera tigris jacksoni)

Case Information

A 4-year-old Malayan tiger, housed at the Bronx zoo in New York, developed a cough and wheezing in March 2020, followed by reduced appetite. The animal was otherwise clinically healthy. Several other tigers in the same exhibit, and 3 lions in a different exhibit, also developed a cough, with a lion having a mild decrease in appetite for a few days. The clinical signs in the first tiger persisted for several days, despite symptomatic treatment. To pursue the cause of the cough, the animal was anesthetized and a tracheal wash was performed and submitted to the Cornell University Animal Diagnostic Laboratory for cytologic analysis and testing for infectious diseases. A direct smear of the tracheal wash was prepared in the laboratory and stained with modified Wright’s stain. View the representative images below and answer the posed questions.

Figure 1: Tracheal wash from a Malayan tiger (20x objective)

Figure 2: Tracheal wash from a Malayan tiger (50x objective)

Figure 3: Tracheal wash from a Malayan tiger (100x objective)


  1. What cells are present in the tracheal wash?
  2. What pathologic process does their appearance indicate?

Answers on next page

Dec 012020

Venous blood from a goat

Case Information

An 18-month-old Nigerian Dwarf doe presented to the Cornell University Equine Nemo Farm Animal Hospital for evaluation of brown-red urine, lethargy, and fever. On physical examination, the goat was tachycardic (110 beats/minute) and had pale brown mucous membranes with a prolonged capillary refill time (estimated to be 8-10% dehydrated). The patient was posturing to urinate with no production. After a 200 mL bolus of fluid was administered to assess dehydration, the doe urinated 5 mL of dark brown-red urine. Blood was drawn for a complete blood count and chemistry panel. Results are shown in the tables below.


Representative images of the blood smear are shown (Figures 1-2). After viewing the images, answer the following questions:

  1. What abnormalities are present in the blood smear?
  2. What pathologic process can be identified?
  3. What are your differential diagnoses?
  4. What is the likely cause(s) for the high MCHC?

Figure 1: Blood smear from an anemic doe (Wright’s stain, 50x)

Figure 2: Blood smear from an anemic doe (Wright’s stain, 100x)


Answers on next page

Sep 052020

Venous blood smear and RBC cytogram from a cat

Case Information

A 17 year old castrated male Domestic Long Hair cat was presented on a weekend to the Cornell University Hospital for Animals Emergency Service for a suspected gastric foreign body diagnosed with abdominal radiography by the referring veterinarian. The cat had a history of chronic kidney disease, which was being managed with a calcium channel blocker (amlodipine) and a renal diet. On physical examination, the cat was quiet and alert with a body condition score of 3/9, pink and tacky mucous membranes, and an estimated 6% dehydration. The cat had a grade 4/6 left parasternal heart murmur with strong regular pulses. Point-of-care bloodwork revealed a blood urea nitrogen concentration of 50-80 mg/dL as measured with an azostix and a packed cell volume of 33%. The cat also had a metabolic acidosis with respiratory compensation and hyperlactemia. The cat was admitted and treated overnight with amlodipine, intravenous fluids, and an anti-emetic (maropitant). An ultrasonographic examination revealed a foreign body in the stomach and bilaterally small kidneys. Surgery was delayed until the cat was rehydrated and stable.

Prior to surgery (48 hours after admission), blood was drawn into vacutainer tubes containing EDTA or no anticoagulant (Becton Dickinson and Co., Franklin Lakes, NJ, USA) for a screening complete blood profile (CBC) (ADVIA® 2120i) and serum biochemical panel (Cobas 501), respectively. The CBC revealed a moderate non-regenerative anemia (hematocrit: 19%, reference interval [RI]: 31-48%; hemoglobin concentration: 6.8 g/dL, RI: 10.9-15.7 g/dL; absolute reticulocyte count: 13.9 thou/μL, RI: 8.5-60.7 thou/μL). Serum biochemical testing showed mild increases in creatinine concentration (2.4 mg/dL, RI: 0.8-2.1 mg/dL) and aspartate aminotransferase (AST, 71 U/L, RI: 17-48 U/L) and creatine kinase (CK, 1951 U/L, RI: 47-386 U/L) activities. View the provided image of the blood smear and RBC cytogram from the hematology analyzer and answer the questions below:

  1. What abnormality is present on the smear and the cytogram plot?
  2. What is the diagnostic relevance of the abnormality?
  3. What would you do next to confirm that the abnormality is a pathologic finding?

Figure 1: Smear and RBC cytogram from an anemic cat

Answers on next page

Jul 152020

Venous blood smear from a Hedgehog

Case Information

A 3.5 year-old, intact male hedgehog presented to Cornell University Hospital for Animals Emergency Service for inappetence, lethargy, and ataxia. The owner had been away for 7 days and left the animal with enough food and water to last the week. Upon return, the owner noticed that the hedgehog had only consumed about 25% of the food and water.  Upon presentation, the patient weighed 304 grams (expected weight, 400-600 grams), had pale mucous membranes and was mildly tachypneic (54 breaths/minute; expected normal, 25-50 breaths/minute). The animal had a normal heart rate of 240 beats/minute (expected normal, 180-280 beats/minute) and temperature (96°F, expected normal, 96-99°F).1  The patient was anesthetized for collection of blood for a complete blood count (CBC) and biochemical panel as well as whole body radiographs. 

The CBC revealed that the animal was anemic (hematocrit, 23%, reference interval [RI], 36-47%2) and had a marked leukocytosis (109.1 x 103/μL, RI, 11.5-21.7 x 103/μL2). The automated platelet count was 277 x 103/μL (no available RI). Biochemical testing revealed a mildly increased creatinine concentration (1.5 mg/dL, RI, 0.5-1.0 mg.dL2) with  normal urea nitrogen concentration (52 mg/dL, RI, 34-57 mg/dL2), and increased liver enzyme activities (alanine aminotransferase [ALT], 269 U/L, RI, 15-29 U/L2, alkaline phosphatase [ALP], 2820 U/L, RI, 18-26 U/L2) and hyperbilirubinemia (3.2 mg/dL, ISIS mean ± SD, 0.5 ± 0.1 mg/dL, Physiological Data Reference Values, International Species Information System, 1996). Representative images of the blood smear are shown (Figures 1-4).

Figure 1: Venous blood from a Hedgehog (Wright’s stain, 50x)

Figure 2: Venous blood from a Hedgehog (Wright’s stain, 50x)

Figure 3: Venous blood from a Hedgehog (Wright’s, 100x)

Figure 4: Venous blood from a Hedgehog (Wright’s stain, 50x)

After viewing the images, answer the posed questions:

  1. What is the lineage of most of the cells represented in the images?
  2. What are your differential diagnoses?
  3. What additional testing can be done to help clarify cell lineages in this species?

Answers on next page

May 132020

Peritoneal fluid from a dog

Case information

A 1-year-old intact male dog was presented on an emergency basis to the Cornell University Hospital for Animals (CUHA) after a blunt traumatic episode.  The dog was quiet, alert and responsive upon physical examination.  Multiple cutaneous abrasions were noted around the right hind leg and inguinal region.  The mucous membranes were tacky and pale pink.  The dog was tachycardic (190 beats per minute) and no overt murmurs or arrhythmias were auscultated. Decreased bronchovesicular sounds were auscultated bilaterally, but there were no crackles or wheezes. The dog was ambulatory in the front legs with paraparesis of the hind legs due to multiple pelvic fractures, which were confirmed on lateral and ventrodorsal radiographs.  There was a bloody preputial discharge and hematuria.

Abbreviated blood work performed in-house revealed a mild hyperglycemia (136 mg/dL; reference interval [RI]: 60 – 120 mg/dL) and hyperlactatemia (4.4 mmol/L; RI: < 2.0 mmol/La) with a normal hematocrit (45%; RI: 41 – 58%) and total solids (7.2 g/dL; RI: 5.9 – 7.8 g/dL).  Initial abdominal FAST scan ultrasound showed no abnormalities.  A repeat heparinized plasma biochemical analysis, performed after treatment and fluid therapy, showed a persistent hyperglycemia (167 mg/dL; RI: 68 – 104 mg/dL) and mild increases in aspartate aminotransferase (AST: 103 U/L; RI: 18 – 56 U/L) and creatine kinase (CK: 3760 U/L; RI: 64 – 314 U/L) activities.  There were no evidence of azotemia (urea nitrogen: 21 mg/dL [RI: 9 – 26 mg/dL]; creatinine: 0.8 mg/dL [RI: 0.6 – 1.4 mg/dL]).  Approximately 15-hours post-hospitalization, there was a small amount of abdominal fluid.  The fluid was aspirated into an EDTA (purple top) tube and submitted to the laboratory for peritoneal fluid analysis.

Provided are the results and representative images from direct and cytospin smears of the peritoneal fluid.

Figure 1: Peritoneal fluid from a dog, direct smear, 20x, Wright’s stain.

Figure 2: Peritoneal fluid from a dog, cytospin smear, 50x, Wright’s stain.

Figure 3: Peritoneal fluid from a dog, cytospin smear, 100x, Wright’s stain.

Using the provided information answer the following questions,

  1. What is the predominant cell population in the sample?
  2. What is your cytologic diagnosis?
  3. What additional test could be considered to further support your diagnosis?

Answers on the next page.


a: Mathews, K.A. (2012). ‘Monitoring Fluid Therapy and Complications of Fluid Therapy’, in DiBartola, S.P. Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice. St. Louis, Missouri: Saunders Elsevier Inc. pp:386–404.