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 every 1-2 months. 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!).
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 and answer the questions below:
Based on the location, pattern of cell arrangement and shape of the cells, what is your primary differential diagnosis?
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)
Tracheal wash from a Malayan tiger (Panthera tigris jacksoni)
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)
What cells are present in the tracheal wash?
What pathologic process does their appearance indicate?
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:
What abnormalities are present in the blood smear?
What pathologic process can be identified?
What are your differential diagnoses?
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)
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:
What abnormality is present on the smear and the cytogram plot?
What is the diagnostic relevance of the abnormality?
What would you do next to confirm that the abnormality is a pathologic finding?
Figure 1: Smear and RBC cytogram from an anemic cat
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:
What is the lineage of most of the cells represented in the images?
What are your differential diagnoses?
What additional testing can be done to help clarify cell lineages in this species?
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,
What is the predominant cell population in the sample?
What is your cytologic diagnosis?
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.
An 8 year old male neutered domestic shorthair cat was presented to an emergency hospital with a 4 day history of vomiting and inappetence. The vomiting was partially responsive to Cerenia® (Maropitant). The owner had also noticed purple mucous membranes. The cat was an indoor cat and may have had access to the bathroom cabinet. On physical examination, the cat had cyanotic mucous membranes, and was hypothermic (97.7ºF), equivocally tachycardic (the heart rate was at upper end of normal limits at 220 beats/minute) and panting (respiratory rate of 100 breaths per minute). A venous blood sample was taken for an automated hemogram and biochemical profile and was observed to be brown. Results are shown below (Figures 1-3).
Figure 1: Hemogram
Figure 2: Automated dotplots
Figure 3: Biochemical panel
The blood was then sent to the Animal Health Diagnostic Laboratory for a blood smear examination and was received 5 days after collection. Examine the images of the Wright’s-stained smear then answer the posed questions.
What abnormalities are evident in the blood smear?
What additional stain can be applied to confirm your observation?
Given the history, what is the likely diagnosis?
What additional testing would you consider?
How would you treat the cat?
Figure 4: Venous blood from a cat (Wright’s stain, 20x)
Figure 5: Venous blood from a cat (Wright’s stain, 100x)
Figure 6: Venous blood from a cat (Wright’s stain, 100x)
A 9 year-old, neutered male American pit bull terrier presented to a private veterinary practice for re-evaluation of a swelling within the interdigital space of P3 and P4 on the left front paw. The swelling was noted 6 weeks before, at which time it was oozing a hemorrhagic, purulent material. The swelling was initially thought to be an interdigital cyst and was treated with an course of antibiotics and a tapering dose of prednisone. The swelling seemed to shrink with treatment but did not resolve completely. At the re-evaluation, the veterinarian performed a fine needle aspirate of the swelling and submitted the smears of the aspirate to the Animal Health Diagnostic Center at Cornell University for examination. Examine the image from the smears below, then answer these questions:
What broad category of tissue cells are present in the sample?
Based on your answer for question 1, what would be your top differential diagnosis for the cause of the mass?
What additional finding is evident in the smears that supports your answer to question 2?
Figure 1: Aspirate of an interdigital swelling (Wright’s stain, 20x objective)
Figure 2: Aspirate of an interdigital swelling (Wright’s stain, 50x objective)
Figure 3: Aspirate of an interdigital swelling (Wright’s stain, 50x objective)
A fine needle aspirate was obtained from a mass lesion on the left hind foot of a nine year old male castrated domestic longhair cat. Smears of the aspirate were submitted to the Animal Health Diagnostic Center at Cornell University for examination. The mass was located over the lateral aspect of the metatarsophalangeal joint. The mass was first noted approximately 2.5 months before sampling. At that time, the owner reported a “pea-sized” mass on the lateral aspect of the paw. The mass grew slowly over the next several weeks and measured 2.3 x 1.4 cm at the time of sampling. The mass was described as a rounded, raised, poorly haired to alopecic, soft to slightly firm, movable, non-painful mass with no deep attachments. The patient did not appear to be bothered by the lesion. The mass was non-painful on physical examination and no lameness or altered grooming behavior were reported.
Examine the provided images from the aspirate of the mass, then answer the following questions:
What general lineage would you assign to these cells?
What are your differential diagnoses for the mass?
Figure 1: Photomicrograph of a mass on the foot of a cat (with calipers)
Figure 2: Aspirate of a foot mass in a cat (Wright’s stain, 100x objective)
Figure 3: Aspirate of a foot mass in a cat (Wright’s stain, 50x objective)
Figure 4: Aspirate of a foot mass in a cat (Wright’s stain, 50x objective)
Figure 5: Aspirate of a foot mass in a cat (Wright’s stain, 100x objective)
A 19 year old Arabian stallion presented for evaluation for the cause of a pleural effusion. A large amount of pleural fluid was identified on thoracic ultrasonographic examination and the fluid was sampled for analysis. The fluid was dark yellow in color and slightly cloudy. Cell counts were low (800 nucleated cells/μL) with a small amount of blood (15.2 thousand RBCs/μL). Total protein by refractometry was mildly increased at 2.7 g/dL. Cytospin preparations of the fluid were prepared for cytological evaluation and were stained with a modified Wright’s stain.
Examine the provided images of the pleural fluid, then answer the following questions:
How would you classify this effusion as to mechanism of formation?
What other stains might you consider applying to this sample?
What is your cytologic diagnosis?
Figure 1: Pleural fluid from a horse (Wright’s stain, 10x objective)
Figure 2: Pleural fluid from a horse (Wright’s stain, 50x objective)
Figure 3: Pleural fluid from a horse (Wright’s stain, 100x objective)
Figure 4: Pleural fluid from a horse (Wright’s stain, 100x objective)
Figure 5: Pleural fluid from a horse (Wright’s stain, 100x objective)