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!).

Some of our cases are available as digital slides. So feel free to look at the actual slide used with the case (when available).

Jun 042022

Venous blood from a cat

Case Information

A 1 year old neutered male domestic shorthair cat was presented to a veterinarian for the primary complaints of chronic upper respiratory symptoms, lethargy, and decreased appetite. The cat was documented to be negative for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) via a rapid test performed at a humane shelter. Upon physical examination, the cat was febrile (104.4°F) and lethargic with bilateral conjunctivitis, prolapsed third eyelids, upper airway congestion and a mucopurulent nasal discharge. The cat was treated with subcutaneous fluids, antibiotics, an antiviral medication (famcyclovir), and an anti-inflammatory medication. The patient showed mild improvement with treatment but symptoms recurred 4 days after the initial examination. A complete blood count (CBC), with an automated white blood cell differential count, performed at the veterinary clinic showed a low normal erythron (hematocrit [HCT], 32%, reference interval [RI], 30-52%) with a marked leukocytosis (218.9 x 103/µL, RI, 2.9-17.0 x 103/µL) characterized by a marked monocytosis (124.6 x 103/µL, RI, 0.1-0.7 x 103/µL) and lymphocytosis (93.6 x 103/µL, RI, 0.9-6.9 x 103/µL). There was a concurrent marked neutropenia (0.5 x 103/µL, RI, 2.3-10.3 x 103/µL) and moderate thrombocytopenia (78 x 103/µL, RI, 151-600 x 103/µL).

The veterinarian submitted an EDTA-anticoagulated blood sample and an unstained blood smear to the Clinical Pathology laboratory in the Animal Health Diagnostic Center at Cornell University for evaluation by a clinical pathologist. On receipt (24 hours after collection), the blood was analyzed with an automated hematology analyzer (Table 1) and a blood smear examination with manual differential count was performed on the submitted blood smear, which was stained with a modified Wright’s stain (Table 1, Figures 1 -3). 

  • What is your diagnosis?
  • What diagnostic tests can be used to further characterize the cells in blood?

Venous blood from a cat (Wright’s, 20x objective)

Figure 2: Venous blood from a cat (Wright’s, 50x objective)

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

Answers on next page

Apr 092022

Aspirate from a left axillary mass in an alpaca

Case Information

An 11-year-old male alpaca was presented to a veterinarian for a mass in the left axilla. The mass had been discovered one year prior during shearing and was approximately 1 x 2 cm and firm on palpation. The mass had grown substantially in the intervening year and was approximately 6 x 6 x 6 cm when examined by the attending veterinarian. No abnormalities were noted in the overlying skin or hair fibers. The mass was non-painful on palpation and appeared cystic superficially with a firmer deep portion that was well-attached to underlying tissues. Aspirates were taken from the superficial and deep portions of the mass and submitted to the Animal Health Diagnostic Center at Cornell University for cytologic evaluation (Figures 1-4). No digital slide is available for this case.

  • What cell types can you identify in the aspirate?
  • What are your differential diagnoses for the mass?

Figure 1: Axillary mass in an alpaca (20x objective)

Figure 2: Axillary mass in an alpaca (20x objective)

Figure 3: Axillary mass in an alpaca (50x objective)

Figure 4: Axillary mass in an alpaca (50x objective)

Answers on next page

Feb 012022

Aspirate from a pectoral mass in a horse

Case Information

A 16-year-old Quarter Horse gelding with a history of low thyroid hormone concentrations was being rechecked for possible pituitary pars intermedia dysfunction (PPID). During blood sampling for measurement of adrenocorticotropic hormone (ACTH), insulin, leptin and thyroxine, a large subcutaneous mass was noted in the pectoral region. A fine needle aspirate of the mass was performed and smears of the aspirate were submitted to the Clinical Pathology laboratory in the Animal Health Diagnostic Center at Cornell University for cytologic evaluation. Examine the representative images of the modified Wright’s-stained smears of the aspirate and then answer the questions below.

  • What cell types can you identify in the aspirate?
  • What are your differential diagnoses for the mass?

Figure 1: Pectoral mass aspirate in a horse (20x objective)

Figure 2: Pectoral mass aspirate in a horse (50x objective)

Figure 3: Pectoral mass aspirate in a horse (50x objective)

Figure 4: Pectoral mass aspirate in a horse (50x objective)

Answers on next page

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. 

Digital slide

Examine the representative images of the smears or view the digital slide (click on the image to the right) 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.

Digital slide

Examine the representative images of the smears or view the digital slide by clicking on the image to the right 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