Case 3 - 170421-3

Nine-year-old, female spayed Australian Shepherd

The patient had a one-year history of progressive, ulcerative skin lesions. The lesions started on her left foot and then began to involve the entire left leg and extended to the cranial aspect of the chest. The lymph nodes on her left side were enlarged and a lymph node aspirate revealed septic inflammation. She had previously been placed on antibiotics with no response.

One punch biopsy of skin from the foot and three punch biopsies from the cranial thorax were submitted. No significant lesions were grossly evident in these small samples.

Three bisected samples of skin are examined in which the dermis is densely infiltrated by nests, cords, and acini of polygonal neoplastic cells which extend to section margins. Neoplastic cells have indistinct cell borders, a moderate amount of eosinophilic, granular cytoplasm, a round to ovoid nucleus with finely stippled chromatin, and one to three variably distinct nucleoli. Anisocytosis and anisokaryosis are moderate and nine mitotic figures are noted in ten, 400x fields. In all sections, lymphatic ducts contain rafts of neoplastic cells. Neoplastic cells multifocally form glandular structures which are frequently filled with proteinaceous material and occasional mineral. Neoplastic cells also occasionally surround necrotic regions filled with karyorrhectic cellular debris. The overlying epidermis is hyperplastic with moderate parakeratosis and forms variably-sized rete pegs. The remaining dermis surrounding the neoplastic population contains large numbers of neutrophils, lymphocytes, plasma cells, and histiocytes.

No special stains.

Haired skin: High-grade carcinoma with lymphatic invasion

The origin of this carcinoma is unclear, it may represent metastasis from an internal organ, or it could be a primary neoplasm from within the skin. Conference participants mentioned that due to the original location being on the foot, the most likely differential is a sweat gland carcinoma. Other differentials which are less likely would include a mammary gland carcinoma or a metastasis from internal organs. Many lymphatics throughout the sections contained neoplastic cells, often occluding the lumens which represents metastasis.