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Histopathological diagnosis
Findings
The right 1st to 4th mammary gland tissue submitted revealed a 4 x 2.5 x 1.7 cm mass in the 1.7th mammary gland area and an enlarged inguinal lymph node measuring 0.9 x 0.4 x 0.4 cm.
The mass was sectioned transversely and six specimens were prepared, including the longitudinal margin of the breast tissue and the inguinal lymph nodes.
In the specimen, a somewhat unclear mammary tumor is observed, mainly consisting of mammary gland tissue.
The tumor cells are cuboidal to polygonal in shape and form irregular tubulopapillary to alveolar structures separated by small amounts of connective tissue.
The tumor cells have round to oval nuclei with prominent central nucleoli and eosinophilic cytoplasm.
There is moderate to severe variation in the size of cells and nuclei, and 1-1 mitotic figures are observed per high-power field.
The tumor tissue has invaded the surrounding adipose tissue. Vascular invasion is also observed. The tumor is not observed at the resection margin in the specimen.
The right inguinal lymph node showed a similar tumor growth, which had almost completely replaced the existing tissue structures.

Histopathological evaluation
Breast tumor: Simple adenocarcinoma of the breast, with right inguinal lymph node metastasis


Comment
Malignant breast tumors were detected in the submitted breast tissue.
Feline mammary gland cancer has a high rate of metastasis even after complete removal.
In this case, the tumor was not observed at the resection margin, but tumor vascular invasion and lymph node metastasis were observed, so caution is required regarding recurrence and metastasis.
Feline mammary adenocarcinoma is an aggressive malignancy that typically exhibits invasive properties and frequently metastasizes to regional lymph nodes and distant sites.
This type of tumor frequently recurs when resection is incomplete.
This tumor occurs more frequently in intact females than in ovariectomized females.
Unlike canine mammary adenocarcinomas, feline mammary adenocarcinomas typically lack estrogen receptors.
Metastasis occurs in at least 25% of cases, usually initially to the axillary or inguinal lymph nodes and at later stages to distant sites including the lungs and pleura.
Recent studies have shown that tumor size is an important prognostic factor.
In this study, cats with mammary adenocarcinomas less than 3cm in diameter had a median survival of 21 months, while cats with tumors larger than 3cm had a median survival of 12 months.



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