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Metastatic nasal carcinoma in a mandibular lymph node aspirate from a cat: Clusters of tumor cells (arrows) are seen among normal lymph node constituents. Pink extracellular matrix (arrowheads) likely reflects a schirrous response.

Impression smear of a biopsy of a thickened duodenum in a French bulldog: A villus Love it when we see tissue architecture in cytologic smears😀

Duodenal biopsy from a dog with chronic diarrhea (same case as last post: Cluster of mucosal epithelial cells (arrow) and increased numbers of small mature lymphocytes (arrowheads). The cytologic diagnosis was lymphocytic inflammation, which was confirmed on histopathology.

Our latest diagnostic challenge: Aspirate of a mass at the thoracic inlet in a hypercalcemuc horse. For the full case go to eclinpath.com/case-1-2025/

Lymph node aspirates from a cat with an aggressive lymphoma: How many mitotic figures do you count in the first image (popliteal lymph node, 20x objective)? In the second image (jejunal lymph node), there are 3 mitoses (arrows, 50x objective).

Macrophages surrounding and phagocytizing dark purple material (presumptive disc material) in the cerebrospinal fluid (CSF) of a 5 year old dog with an acute non-compressive nucleus pulposis extrusion. It is rare to see such material in CSF taps.

Another image from our previous post of a dog with an acute non-compressive nucleus pulposis extrusion. This time you’re looking at a macrophage with phagocytized myelin (pink granules and whorls).

Mediastinal mass in a 9 year dog: Extramedullary acute myeloid leukemia (AML). Blasts have purple cytoplasmic granules, a feature of AML. The diagnosis was confirmed by flow cytometry. The tumor cells were CD34+, CD80+, CD11b+ and MHCII-. For more see Pubmed ID: 39540621.

Cells behaving badly😖 Xenocannibilism -erythrocyte uptake by a non-phagocytic tumor cell (arrowhead) and an aberrant mitotic figure (arrow). Aspirate from a sarcoma, likely chondrosarcoma, arising in the rib of a dog.

Aspirate of a rib mass in a dog (same case as last post). Note how the tumor cells are embedded in light pink matrix, resembling mucin (first two images). The matrix was chunkier and globular in other areas, resulting in a presumptive diagnosis of chondrosarcoma.

Last image from the aspirate of the chondrosarcoma in a rib of a dog: The arrowed cell is an osteoclast, indicating osteolysis.

Aspirate of a mass on the face of a 10 year old cat: Squamous cell carcinoma with neutrophilic inflammation. The aspirate contained many neutrophils and keratinized squamous cells, which were dysplastic (retained viable nuclei, elongate tailing shapes, multinucleation).

Our latest diagnostic challenge: Imprint of a vertebral mass in a cat with paraplegia. For the full case, go to eclinpath.com/case-2-2025/

Avian parasite compilation. Top row: Hemoproteus; second row: Plasmodium; third row: Leukocytozoon; J: Atoxoplasma; K: Babesia mimic (degrading organelle, presumptive); L: Microfilaria

Blood smear from a 3-year-old cat: Macrophages containing phagocytic debris in their cytoplasm were present at the feathered edge. These cells in blood indicate underlying disease, which in this case was feline infectious peritonitis.

Blood from a bearded dragon with inflammation: Arrow: Toxic band heterophil A: Azurophil RL: Reactive lymphocyte T: Thrombocyte Arrowhead: Polychromatophil

Xanthine crystals in urine from two dogs on allopurinol therapy. The crystals can be misidentified as ammonium biurate but they are insoluble in hydrochloric acid (HCl) and sodium hydroxide (NaOH, < 1N). Ammonium biurate are soluble in HCl and NaOH.

Blood smear from a cat: There are numerous Heinz bodies, which are readily visualized in ghost red blood cells and reflect oxidant injury. The cat had hemoglobinuria, indicating concurrent intravascular hemolysis. The cause of the oxidant injury was not ascertained in this case.

Very hungry macrophages😫 Hemophagocytic histiocytic sarcoma in a liver aspirate from a 9 year old Golden Retriever. The cells demonstrated prominent erythrophagia. Note the binucleated erythrophagocytic macrophage with large nuclei (arrow, second image).

Aspirate of a mediastinal mass in a 4 year old dog: Large lymphocytes with a focus of red granules in the cytoplasm (arrow, image 4) dominate with a few small lymphocytes (arrows, images 1-3). A lymphoma of granular lymphocytes is rare in this location.