Cytology of lumps and bumps (Proceedings) - Veterinary Healthcare


Cytology of lumps and bumps (Proceedings)


Cutaneous lymphosarcoma

Cutaneous lymphosarcoma may be seen as a single modular lesion (often at the mucocutaneous junctions) or it may present as multiple nodules throughout the skin. With time, the tumor generally disseminates widely throughout the body.

Morphology is that of a typical lymphosarcoma arising in any other site. Aspirates are generally quite cellular and are comprised of a uniform population of round cells with scant cytoplasm and vesiculate nuclei often containing prominent and irregularly shaped nucleolar whorls. Mitoses may be present but are not common in the author's experience.

Transmissible venereal tumor (TYT)

TVT's generally occur on the genitalia or around the nose and mouth. These tumors may be either self-limiting and regressive or malignant with significant metastases. The eye is a relatively common site of metastatic disease.

Histologically TVT's are often confused with lymphosarcoma but cytologically they are usually quite distinctive. TVT's are comprised of individual large round cells, much larger than the cells of lymphosarcoma. Nuclei are usually very round and centrally located. Cytoplasm is gray to pale blue and often contains numerous distinctive small vacuoles at the cell periphery. Tumor cells generally exhibit significant variation in nuclear size and nuclear/cytoplasmic ratios. Mitotic index is high and abnormal mitoses may be seen. The tumor aspirates often contain significant numbers of infiltrating lymphocytes, plasma cells, and macrophages.


Cutaneous plasmacytomas are generally benign tumors and may be located either in the skin or mouth. In the mouth they are most common in the gum adjacent to teeth. Aspirates collected from these tumors are usually quite cellular and are comprised of a relatively uniform population of discrete oval to round cells with eccentric round nuclei, pale perinuclear zones and abundant gray-glue to deep blue cytoplasm. Some multinucleated cells may be present. Tumor cells are remarkably reminiscent of normal plasma cells and are usually easily distinguished from the other round cell tumor types.

Mast cell tumor

Cutaneous mast cell tumors may arise as single or multiple nodules. Single nodules may be benign but if they recur or additional nodules appear later, they should be regarded as malignant. Multiple nodules are always regarded as potentially malignant. As in the case of melanoma, cytomorphology does not predict potential for malignancy in these tumors.

Aspirates taken from mast cell tumors are generally quite cellular. The predominant cell is the tumor cell but eosinophils may also be abundant and fibroblasts may be present in low numbers. Tumor cells are round to oval with round central nuclei. The diagnostic feature is the presence of variable numbers of deep purple cytoplasmic granules which may be so numerous as to obscure nuclear detail. When quick stains are used, cytoplasmic granules may not be seen. If mast cell tumor is suspected but no granules are present, it may therefore be useful to reaspirate the mass and stain either with a standard Wright's stain or new methylene blue which will also highlight the granules.


Click here