Round cell tumor

From Dog
Ulcerated cutaneous round-cell tumor caudal to the left scapula of a 4-year-old male Hovawart dog[1]

Round cell tumors (Desmoplastic small-round-cell tumor) are a malignant neoplastic soft tissue sarcoma of younger dogs.

Mast cell tumors are the most frequent round cell tumors in dogs[2] but can also be observed in atypical anal sac adenocarcinomas[3], lymphomas, melanomas, plasmacytomas, transmissible venereal tumors, histiocytomas, primitive neuroectodermal tumor, Merkel cell carcinomas and hepatic neuroendocrine tumors.

These tumors can affect the skin, kidneys, liver[4], bone marrow and spleen.

These tumors are usually rapidly growing cutaneous masses which are often non-pruritic and non-painful on palpation. They are sometimes associated with epitheliotrophic lymphoma[5].

Paraneoplastic diseases may be associated with this condition such as polymyositis[1].

Histologically, these tumors appear as a monomorphous population of atypical round cells with round to oval to indented and pleomorphic nuclei, abundant eosinophilic homogenous cytoplasm, anisocytosis, anisokaryosis, atypical mitoses and associated necrotic areas.

A differential diagnosis would include mast cell tumor, sebaceous adenoma, sebaceous carcinoma, Merkel cell carcinoma and squamous cell carcinoma.

Treatment is usually curative with wide-margin surgical excision but due to the malignant nature of these tumors, recurrence should be considered and regular monitoring is recommended.


  1. 1.0 1.1 Gianella P et al (2012) Primary cutaneous undifferentiated round cell tumor with concurrent polymyositis in a dog. Can Vet J 53(5):549-553
  2. Mackowiak II et al (2012) E-cadherin in canine mast cell tumors: Decreased expression and altered subcellular localization in Grade 3 tumors. Vet J 194(3):405-11
  3. Sakai H et al (2012) Cytologically atypical anal sac adenocarcinoma in a dog. Vet Clin Pathol 41(2):291-294
  4. Warren-Smith CM et al (2012) Lack of associations between ultrasonographic appearance of parenchymal lesions of the canine liver and histological diagnosis. J Small Anim Pract 53(3):168-173
  5. Shiomitsu K et al (2012) Cutaneous epitheliotropic lymphoma with dual CD3 and c-kit expression in a dog. Vet Clin Pathol 41(4):594-598