99mTc-labeled dextran for mammary lymphoscintigraphy in dogs

Lymphoscintigraphy is the technique of choice for sentinel lymph node detection in women with early breast cancer, but there is limited information evaluating the value of this technique in animals. We investigated mammary lymphatic drainage in 25 young female mongrel dogs by intramammary injection of 18.5 MBq of 99mTc-dextran (70,000 Da). Lymph node anatomical referencing was obtained using an external marker, bone scintigraphy, or scintiscanning the body contour. Cranial and caudal thoracic mammary glands drained into the cranial sternal lymph node and axillary lymph center. The cranial thoracic mammary gland also drained into the superficial cervical lymph node in two of five animals. The cranial abdominal gland was drained by the axillary lymph center. The caudal abdominal mammary gland was drained by the superficial inguinal lymph node in all animals and simultaneously by medial iliac lymph nodes in four of five animals. In one dog, this mammary gland was also drained by the mediastinal and the superficial cervical lymph nodes. The inguinal mammary gland was drained by superficial inguinal lymph nodes and simultaneously via the medial iliac lymph node in one animal. Lymphatic communications between lymph nodes were identified in 11 of 25 (44%) animals. 99mTc-dextran mammary lymphoscintigraphy was easy and rapid to perform and may provide valuable information for further studies.     

Sentinel lymph node mapping of the canine anal sac using lymphoscintigraphy: A pilot study

Sentinel lymph node mapping and biopsy are important parts of oncologic staging in human medicine. Sentinel lymph node mapping enables identification of the first lymph node to receive lymphatic drainage while avoiding unnecessary lymph node dissection. Anal sac adenocarcinoma is the most common malignant neoplasm of the canine perineal area. For dogs with anal sac adenocarcinoma, lympadenectomy and metastasis to the iliosacral lymphocentrum are negative prognostics indicators. The objectives of this prospective, two by two, crossover pilot study were to establish the feasibility of lymphoscintigraphy using Technetium‐99 sulfur colloid of the canine anal sac of healthy dogs, compare two injection techniques, and the time for identification of sentinel lymph nodes using each technique. We hypothesized that both intramural and perimural injections of the canine anal sac would identify similar sentinel lymph node drainage. The sentinel lymph node was identified in all dogs using either technique. Intramural injection of the canine anal sac showed radiopharmaceutical uptake faster than perimural injection technique (P = 0.040). There was concordance between intramual and perimural techniques for the sentinel lymph node identified in 50% of cases. A sacral lymph node was identified as sentinel in three of eight dogs (37.5%). Lymphoscintigraphy of the canine anal sac is safe and feasible in normal dogs; however, the method of injection technique seems to have a significant effect on the sentinel lymph node identified.     

CANINE VENTRAL BODY WALL LYMPHOSCINTIGRAPHY

The scintigraphic characteristics of lymph nodes draining the ventral body wall were analyzed in 12 dogs as to their pattern of appearance and image contrast. Each dog was scanned using ^99mTc-antimony sulfide colloid and ^99mTc-dextran, and the imaging characteristics of these agents were compared. A large degree of variability exists in the number and pattern of lymph node appearance with either agent. No significant difference in average numbers of lymph nodes per dog was shown between agents. However, ^99mTc-antimony sulfide colloid provided a significantly (p<.05) better target-to-background ratio, which determines the contrast with which lymph nodes stand out from background activity. From these findings, it is suggested that too great a variability in lymph node appearance exists using this procedure to allow a high degree of confidence in the diagnosis of metastasis to lymph nodes of the ventral body wall. However, for other purposes, ^99mTc-antimony sulfide colloid is the lymphoscintigraphic agent of choice.     

A review of sentinel lymph node evaluation and the need for its incorporation into veterinary oncology

Being the first lymph node or nodes to which many primary tumours reliably drain, the disease status of the sentinel lymph node/s (SLN) is important in the prediction of survival. SLN identification and biopsy are critical in the staging of human cancers. The status of the SLN helps determine prognosis and shape treatment plans. SLN evaluation is currently not routinely performed in veterinary oncology, not even at specialty oncology practices. Given the prognostic importance of lymph node involvement in tumours such as mammary gland carcinoma, osteosarcoma, synovial cell sarcoma and mast cell tumours, SLN evaluation should be incorporated into routine clinical practice so as to improve our clinical assessment of veterinary oncologic patients.