Chondrosarcoma Congenital in a Pelvic Member of one Puppy

Background: Chondrosarcomas, malignant neoplasms of mesenchymal origin, are characterized by the proliferation of cartilage cells. They usually affect middle-aged to older dogs and large to giant breeds, rarely occurring in other age groups and small dogs. Limb amputation typically leads to survival. The diagnostic process involves clinical and orthopedic examinations, blood count, blood chemistry test, radiography, computed tomography, cytology, biopsy, and confirmation through histopathological examination. This study aimed to describe an unusual case of congenital chondrosarcoma in the calcaneal region of the left pelvic limb of a pug puppy. Case: A 42-day-old male pug was treated for a non-ulcerated, poorly delimited, firm, and nonfluctuant nodule, with a diameter of approximately 4 cm, on the left pelvic limb. A sample of the nodular region was collected by fine-needle aspiration cytology, with findings suggestive of malignant mesenchymal neoplasia. Radiographic screening did not detect metastases. Pelvic limb amputation was performed 10 days after the examinations, and the operation was uneventful. A tumor mass sample was sent for histopathological examination. Microscopic examination revealed proliferation of fusiform to stellate mesenchymal cells in a desmoplastic fibrous stroma and a nodular area of irregular hyaline cartilage formation. One month following surgery, the patient presented with dyspnea, cough, and pale mucus membranes. A follow-up radiographic ventrodorsal thoracic study revealed a multinodular interstitial pattern in the right lobes, compatible with metastatic nodules. The histopathological findings were compatible with chondrosarcoma. Owing to its condition, the animal was euthanized. Discussion: The diagnosis of chondrosarcoma is established based on clinical signs and macroscopic, cytological, and histopathological findings. Chondrosarcomas typically affect large-breed, adult, or older dogs and rarely occur in young, small-breed animals, which highlights the rarity of the presented case, where the patient was a 42-day-old pug. Skeletal chondrosarcomas affect the nasal cavity, which is the most common site in dogs, followed by the ribs, long bones, pelvis, vertebrae, digits, and penile bone. In the present case, the tumor was located in the pelvic limb, within the region of the long bones. Chondrosarcomas in limbs typically present with pain and lameness of the affected limb. However, despite the nodule’s size relative to the animal, lameness and pain were not reported. Chondrosarcomas are slowly progressing neoplasms with a low incidence of metastasis, accounting for approximately 18% of cases in dogs. Even after amputating the affected limb, an effective treatment option, the patient exhibited an extremely rapid and aggressive clinical progression, which included dyspnea and cough, leading to confirmation of pulmonary metastasis through chest radiography. This finding contradicts the existing reference literature, which suggests the rarity of metastases in these cases. The presented case represents an atypical presentation of malignant neoplasia in a young pug when compared with literature data. The etiology of this neoplasia remained undetermined in this patient, which underscores the importance of this case report and highlights the need for further studies to determine the origin of such neoplasias in puppies. Keywords: amputation, chondrosarcoma, mesenchymal, neoplasm.