Mammary intraductal carcinoma

• Name: Akira
• Report and medical history: canine, Siberian Husky, female neutered, 12 years old.

Approximately three months before presentation, a progressively enlarging subcutaneous mass developed in the right inguinal region, adjacent to the right inguinal mammary gland. Clinical examination revealed a firm, mobile, irregularly surfaced, and mildly painful subcutaneous lesion measuring ~6 cm. Bloodwork results were unremarkable.

Cytological evaluation revealed hemorrhagic samples with abundant macrophages containing hemosiderin and numerous erythrocytes, within a proteinaceous background. Findings were consistent with a cystic lesion with a hemorrhagic component.
After surgery, following an excisional biopsy of the lesion and regional lymph node, a histopathological examination revealed mammary intraductal carcinoma associated with ductal papillomatosis. The inguinal lymph node showed only mild follicular hyperplasia, and no evidence of metastatic disease.

This case provides a useful insight for clinicians encountering subcutaneous inguinal lesions with a multilobulated, cystic appearance on ultrasound. To the authors’ knowledge, this ultrasonographic presentation of mammary intraductal carcinoma has not been previously reported in dogs. Awareness of this unusual manifestation may help guide differential diagnoses and emphasize the need to consider neoplasms in inguinal subcutaneous lesions that appear cystic.