Mastitis and Periareolar Necrosis by 1% Methylene Blue after Axilar Lymphadenectomy and Regional Mastectomy in a Bitch

Abstract

Background: Mammary neoplasms are frequent in dogs, and surgical excision by radical unilateral mastectomy is the first-choice treatment for most cases. Typically, inguinal lymphadenectomy is performed during mammary inguinal excision, whereas axillar lymphadenectomy is performed using dyes to guide surgical dissection and avoid iatrogenic trauma. This study reports the case of a bitch that underwent axillar lymphadenectomy and regional mastectomy. In this way, this work has the objective of reporting the case of a bitch referred to mastectomy and lymphadenectomy, which presented complications due to the use of 1% methylene blue.Case: A 15-year-old female intact poodle weighing 6.2 kg presented with mammary nodules. Cytological examination confirmed malignant neoplasm in the mammary gland classified as Grade II (World Health Organization). Radical unilateral mastectomy and regional lymphadenectomy were performed. The surgical procedure involved intradermic injection of 0.5 mL of sterile 1% methylene blue solution around the right cranial thoracic mammary gland divided in four sites before skin incision. Following right axillar lymphadenectomy, instead of radical unilateral mastectomy, regional mastectomy was performed in two ulcerated nodules at the right cranial abdominal gland to shorten the surgery time after the bitch demonstrated severe trans-operative hypotension. The bitch was monitored during anesthetic recovery and was discharged after stabilization. At fourteen days after surgery, the patient was re-examined. Increased volume and pain in the mammary glands of both chains were observed. In addition, a whitish liquid secretion was noted primarily from the thoracic caudal left and thoracic cranial right mammary glands. The last mammary gland also presented a periareolar black area where the dye was applied. Progressive remission of the clinical signs was observed after therapy with amoxicillin and clavulanate (20 mg/kg/BID/15 days) and meloxicam (0.1 mg/kg/SID/3 days). At 60 days after surgery, the patient presented minor signs of mastitis at the left caudal thoracic mammary gland.Discussion: In humans, methylene blue is avoided because of rapid diffusion after injection, which could be associated with mastitis due to fat necrosis. The risk of this complication is reduced when tissue ipsilateral to the dyed lymph node is completely excised. In this case, the ipsilateral lymph node chain was not completed excised because of anesthetic complication, and periareolar necrosis was observed at the methylene blue injection site. This complication may be the result of methylene blue oxidation, which can produce formaldehyde and deamidated oxidation products. Methylene blue leads to vasoconstriction of arterioles and tissue ischemia when used in concentrated solutions. Furthermore, a 1% solution has a pH of 3-4.5, which increases its cytotoxic effect. Studies suggest that mammary neoplasms may promote local lymphatic alteration, as observed in this case, including inflammatory response at the contralateral chain that receives dye injection. This suggests that the dye is drained by lymphatic vessels and causes mastitis in the remaining mammary glands. Therefore, methylene blue can cause mastitis and tissue necrosis at the injection site, as well as in the contralateral chain in cases where radical unilateral mastectomy is not performed. This complication increases the morbidity associated with the procedure. However, in the present case, the treatment was sufficiently adequate to restore the patient’s condition.