The impact on staging of no-palpable lymph node extirpation in single cutaneous mast cell tumor in dogs : a multicenter study

Metastasis to regional lymph nodes (RLN) in cutaneous mast cell tumor (cMCT) in dogs were correlated with contraction of survival time and high risk of spreading to distant sites. The extirpation of RLN in dogs with cMCT has been suggested in presence of lymphoadenomegaly, suspected or certain cytological lymph nodes metastasis.[1] On the contrary 29% of dogs with metastasizing grade II cMCT had normal size RLN and 18% of cMCT at first presentation had RLN involvement.[2,3] In this study no palpable or normal size regional lymph node extirpation was included in the surgical management of cMCT in dogs. The lymph node status was assesed using a recent histologic classification[4] and possible correlations with tumour variables were analized. Ninety-three dogs with single MCT without distant metastasis that underwent wide surgical excision and no palpable or normal size RLN extirpation were included. Data collected were: breed, age, weight, sex, site and size of cMCT, ulceration, presentation (first vs recurrence), 3-tier and 2-tier histological grades, histological margin status (clean vs dirty), RLN location, RLN histological status[4] and admission to adjuvant oncological treatment. The association between nodal status and tumor variables was analyzed by a generalized linear model with multinomial error. Thirty-three (35.5%) lymph nodes were HN0, 14 (15%) were HN1, 26 (28%) were HN2 and 20 (21.5%) were HN3. The presence of positive no palpable RLN was significantly associated with cMCT located in the genital region and with cMCT larger than 3 cm. Forty-four dogs received adjuvant chemotherapy. Mean and median follow-up time were 695 and 504 days, respectively (range, 10-2429). Loco-regional relapse with a positive lymph node was detected in 5 cases with a time ranged to 52 to 1071 days from surgery. Metastatic spread to spleen and liver was identified in 5 dogs with a time ranged from 52 to 1071 days (3 out of this 5 dogs had also the loco-regional relapse). Lymphatic metastases play a crucial role in predicting a correct prognostication and recommendations for adjuvant therapies. These results confirmed the high probability of lymph node metastasis even for no palpable or normal size RLN for dogs with cMCT. No strong association were found to predict the lymph node status. The relative low number of loco-regional and distant metastasis led to the hypothesis that lymph node extirpation could also have a terapeutical value, but further prospective studies are needed.