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!).
A 7 year old castrated male mixed breed dog presented with a 9 month history of intermittent watery, mucoid and bloody diarrhea, which was not completely responsive to medical therapy and a hypoallergenic prescription diet. The patient subsequently developed panuveitis and was referred to Cornell University Hospital for Animals after starting treatment with prednisolone acetate eye drops and oral prednisone (5mg twice daily). Upon initial presentation, most of the physical examination was unremarkable, except there was still bilateral panuveitis, with 50 and 100% retinal detachment in the right and left eyes, respectively. A subretinal aspirate was performed of the left eye and submitted for cytologic evaluation.
Evaluate the provided cytologic images (Figures 1-3) and answer the following questions:
What differential diagnoses would you have for this patient based on the history?
What are the rod-like structures within the macrophages and scattered in the background?
What additional tests would you recommend?
Figure 1: Subretinal aspirate from a dog (Wright’s stain, 50x objective)
Figure 2: Subretinal aspirate from a dog (Wright’s stain, 100x objective)
Figure 3: Subretinal aspirate from a dog (Wright’s stain, 100x objective)
Aspirate from a subcutaneous mandibular mass in a cat
An 18 year old male neutered Domestic Shorthair cat presented to the Cornell University Hospital for Animals (CUHA) Emergency Service for evaluation of a subcutaneous left mandibular mass and inappetence. The mass had been previously incised by the primary veterinarian and had yielded purulent material. At that time, treatment with doxycycline was started, however the mass continued to increase in size. At the time of presentation to CUHA, the mass was approximately 2 x 2 x 0.5 cm, not painful on palpation, and not freely movable. Fine needle aspirates were taken from the mass for cytologic examination. Examine the representative images of the smears and answer the questions below:
What are the cells marked by the red and blue arrows in Figure 2?
What are your top differential diagnoses for the structures within the cells in Figures 3 and 4?
What additional testing would you recommend?
Figure 1: Aspirate of a left caudal mandibular mass from a cat (20x objective, Wright’s stain)
Figure 2: Aspirate of a left caudal mandibular mass from a cat (50x objective, Wright’s stain)
Figure 3: Aspirate of a left caudal mandibular mass from a cat (100x objective, Wright’s stain)
Figure 4: Aspirate of a left caudal mandibular mass from a cat (100x objective, Wright’s stain)
Aspirates from an abdominal and cutaneous mass in a dog
A neutered 8 year old Staffordshire Terrier mixed breed dog presented for re-evaluation of skin masses. Two subcutaneous (presumably ultraviolet light-induced) hemangiosarcomas had been surgically excised in the past. On examination, the dog had multiple red cutaneous lesions on the medial aspect of both hindlimbs and similar small lesions on the caudal abdomen. In addition, the dog had a subcutaneous mass on the right lateral distal hindlimb. Imaging for tumor staging revealed an abdominal mass cranial to the bladder. Aspirates were taken from two of the red cutaneous lesions (one on the right medial hind leg, one on the left medial hind leg), the subcutaneous mass on the right lateral distal hind leg and the abdominal mass. Examine the images of the smears from the right lateral distal hind leg and abdominal mass and answer the questions below.
What types of cells are found in the smears from each mass?
What is your cytologic diagnosis for each site?
Do you think the abdominal mass is related to the skin mass?
Figure 1: Aspirate of the right lateral distal hind leg mass (20x objective, Wright’s stain)
Figure 2: Aspirate of the abdominal mass (20x objective, Wright’s stain)
Figure 3: Aspirate of the abdominal mass (20x objective, Wright’s stain).
Figure 4: Aspirate of the abdominal mass (50x objective, Wright’s stain)
Cauliflower-like mass at the base of the penis of a dog
A 2-year-old castrated male mixed breed dog presented to the Cornell University Hospital for Animals (CUHA) Surgery Service for surgical revision of a previously amputated hind limb. The dog was rescued from the streets in Africa a few months prior and had partially amputated and infected right and left hindlimbs. The dog underwent a complete right hindlimb amputation with no complications. During post-operative care, a urinary catheter was placed and a 4.5cm x 3.4cm x 3.4cm cauliflower mass was observed at the base of the penis. The mass was friable, producing a mild serosanguinous discharge. Impression smears of the mass were taken and submitted to Clinical Pathology for microscopic examination.
Evaluate the provided representative images from the mass and answer the following questions:
What is the top differential diagnosis?
What is the significance of the other cells present?
What is the main route of “infection”?
Figure 1: Impression smears from a penile mass in a dog. Wright’s stain, 10x.
Figure 2: Impression smear from a penile mass in a dog. Wright’s stain, 50x.
Figure 3: Impression smear from a penile mass in a dog. Wright’s stain, 100x.
A 7 year old male castrated English Bulldog was presented to Cornell University Veterinary Specialists (CUVS) for further evaluation of an aggressive bone lesion. The dog initially presented to the referring veterinarian for a one week history of lameness. The dog was noted to be painful on palpation of the left elbow and shoulder. Radiographs of the left limb revealed an aggressive lesion in the proximal half of the left humeral diaphysis, distal to the metaphysis, characterized by indistinct / mottled intramedullary and cortical lysis with adjacent periosteal new bone formation on the caudal cortex. There was no apparent soft tissue swelling. Three-view thoracic radiographs were performed, and there was no evidence of metastatic disease. At CUVS, a fine needle aspirate was performed of the bone lesion and submitted for cytologic evaluation.
Evaluate the provided cytologic images and answer the following questions:
1. What are you differential diagnoses for the bone lesion based on the radiographic description?
2. Which of these differentials is favored given your cytologic interpretation?
3. What additional testing is recommended?
Figure 1: Fine needle aspirate of an aggressive bone lesion in a dog. (Wright’s stain, 20x objective)
Figure 2: Fine needle aspirate of an aggressive bone lesion in a dog.(Wright’s stain, 50x objective)
Figure 3: Fine needle aspirate of an aggressive bone lesion in a dog. (Diff-Quik stain, 100x objective)
Figure 4: Fine needle aspirate of an aggressive bone lesion in a dog. (Diff-Quik stain, 50x objective)
A Brown Swiss bull calf presented to Cornell University Equine Farm Animal Hospital for evaluation of a left humeral fracture. On presentation, the calf was obtunded, recumbent and unable to bear weight. The calf had a body condition score of 2/5 with severe muscle atrophy. Capillary refill time was approximately 2 seconds, but mucous membranes were noted to be pale pink. The heart rate and temperature were within normal limits, while the respiratory rate was 18 breaths per minute with bilateral cranioventral harsh lung sounds, increased respiratory effort and crackles.
Thoracic ultrasonographic and radiographic examination revealed severe bilateral cranioventral lung consolidation, and radiographic examination of the left humerus revealed a complete, comminuted, mid-diaphyseal fracture. Blood was collected for a complete blood count and chemistry panel, and a transtracheal wash was performed and submitted for cytologic examination.
Blood work revealed mild inflammation characterized by a reactive thrombocytosis (907 thou/uL; reference interval [RI]: 252-724 thou/uL) and mild hyperfibrinogenemia (700 mg/dL; RI 100-600 mg/dL, by heat precipitation) with an acute phase response represented by a mild hypoalbuminemia (2.4 g/dL; RI: 3.3-4.3 g/dL) and mild decrease in total iron binding capacity (TIBC, 286 ug/dL; 320-490 ug/dL). A mild hypocalcemia (8.7 mg/dL; RI: 8.9-10.9 mg/dL) was attributed to the hypoalbuminemia (decreased protein-bound fraction).
Images of the transtracheal wash are provided. Evaluate the photomicrographs and answer the following questions:
Which is/are the predominant cell(s) population in the tracheal wash?
Based on the images, what are your differential diagnoses?
What further tests should be performed?
Figure 1: Tracheal wash in a bull calf (Wright’s stain, 20x objective)
Figure 2: Tracheal wash in a bull calf (Wright’s stain, 100x objective)
Figure 3: Tracheal wash in a bull calf (Wright’s stain, 100x objective)
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.
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).
Is a cause for the chronic respiratory disease in the herd evident in the tracheal wash samples?
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?
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
Absolute retic count
White blood cells
Mild toxic change in neutrophils
Total Protein (ref)
Red blood cells
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:
What is the best interpretation for the leukocytosis?
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)
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:
How would you classify the inflammation?
Can you identify the cause of the inflammation?
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)