Foxy, an 11-year-old, F/S Shar Pei presented for vomiting, decreased appetite, and distended abdomen with peritoneal effusion confirmed on AUS. Additional diagnostic testing pending at the time of submission.
A concentrated preparation of abdominal fluid was submitted.
The sample on the slide has a thick blue appearance, which can indicate a high protein concentration, high cellularity, or both.
At 10x magnification, the sample appears very cellular, with the left side having intact cells while those further to the right appear deteriorated, either due to staining or actual disruption. From this magnification, the appearance suggests a round cell population, but it is important to look closer.
At 60x magnification, there is a discrete round cell population. These cells have scant dark blue cytoplasm and large round nuclei, features of lymphoid cells.
A mitotic figure is seen in a cell above (black arrow), where the nucleus takes on a ropey appearance as the chromatin condenses for cell division. Cancers can have increased “mitotic activity” and in certain types of cancer, this is used as a criterion of malignancy, but is typically evaluated on biopsy samples where tissue architecture is maintained. Mitotic activity is also part of normal cell division in healthy tissues, as well as increased in some benign tumours (eg. histiocytomas), so this is only one of many features evaluated.
Note the size spectrum of the neoplastic (cancerous) cells. Two neutrophils are present for size comparison, and most of the neoplastic cells are larger, consistent with large lymphocytes, but some are smaller. While there is a size spectrum, the majority are large and they all have similar morphology.
Neoplastic effusion; large cell lymphoma.
How does rapid turnaround for this report impact case management?
Foxy has non-specific clinical signs that could be from treatable conditions, but this sample immediately demonstrates that she is very sick. Her condition will require difficult decisions for both the veterinarian and owner regarding whether it is appropriate to stabilise her and pursue treatment, or if euthanasia is the most clinically appropriate and humane decision.
Interpretation of fluids often includes a descriptor regarding the type of fluid based on cellularity and protein concentration. These descriptors include transudate, modified transudate, protein rich transudate, and exudate. Clinical pathologists can vary in how they write fluid interpretations, with emphasis on the criteria descriptors, cellular composition, or a combination. Often there is additional information provided in the comments section. Even though this sample cannot be definitively classified as a transudate versus exudate based on total cellularity (sample was centrifuged), those qualifiers become unnecessary when the cell population as a whole is neoplastic. The bottom line is neoplastic effusion.
The type of neoplasia may be included, if obvious, or suggested in the interpretation with reference to the comments. This is especially true in fluids where suspended cells can have distorted morphology. In this case, this appears morphologically consistent with large cell lymphoma, however hematopoietic neoplasms (cancer associated with lymphocytes or blood cell precursors in the bone marrow) can appear very similar on microscopic exam, but be different cell lineages when molecular diagnostics are performed, which is why flow cytometry and PARR (PCR for antigen receptor rearrangements) may be suggested in the comments.
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