Lower number of nevi correlate with ticker melanomas and lower serum tryptase levels: first results and clinicopathological features

Introduction:tryptase is a serine protease with pleiotropic biological activities, that is stored in mast cells (MCs) and less abundantly in blood basophils. Serum tryptase(ST) level is commonly considered to be related to the total number of MCs, that are increased in several malignancies. At the same time, it is known that patients with a higher number of nevi show often thin melanoma(MM),also due to a greater number of dermatological visits. According to these findings, we decided to investigate the correlation between general number of nevi, Breslow thickness and ST. Material/methods:ST was assessed within 20 days after the removal of the primary MM. All samples of ST were assayed at the same laboratory and ST less than 11.4 ng/ml was considered to be within the normal range. We excluded from the analysis patients with anaphylaxis, hereditary/acquired angioedema, immunological dysfunctions, clonal/non clonal hematologic disorders and internal malignancies, as well as patients with atopy and/ or asthma. We also excluded patients with recent intake of antihistamines (≤ 30 days).Sex,age (≤ 60 or ≥ 61),anatomical sites(axial versus peripheral sites),Breslow thickness (≤ 1 or ≥ 1.01 mm), ulceration, and mitotic rate were used as variables for each patient. General number of nevi has been performed using a dichotomous scale( ≤10 versus ≥ 11). Results:a total of 27 patients were included in the analysis. Mean age was 61 years (ranging between 20 and 85 years;19M:8F). Mean Breslow thickness was 0.9 mm (ranging between in situ -8mm), among them 7 patients showed a thickness ≥1.01mm, while 20 patients showed a Breslow thickness ≤ 1.00 mm. Specifically, 4 out of 7 patients with a thickness ≥1.01mm showed a general number of nevi ≤10, while only 4 out of 20 patients with MM ≤1.01mm showed a number of nevi≤10. Mean ST levels of the general cohort was 7.84ng/ml (ranging between 1.52 and 21 ng/ml). Patients with a thickness ≥ 1.01 mm showed ST level lower than patients with a thickness≤ 1.00 mm, respectively, 7.14 versus 8.1 ng/ml. Finally, patients with nevi ≤ 10(n= 8) showed ST level lower that patients with a general number of nevi ≥ 11(n=19), respectively 4.38 versus 8.7 ng/ml. Conclusions: the presence of MCs within melanocytic lesions is a well-documented phenomenon. C-kit and its ligand SCF seem to be crucial for the maturation, survival and migration of both melanocytes and MCs. However, the clinical significance of the MCs and their role in the development and progression of melanocytic tumors remains controversial. Our data show that ST is higher in patients with an higher number of nevi, stressing that MCs and ST play a pivotal role in the proliferation of melanocytes.We observed a progressively decreasing of ST levels in thicker MM and that patients with ticker MM showed a lower number of nevi. Our results highlight that ST may play a role in the early stage of the tumorigenesis, for the development of multiple benign nevi and thin MM; nevertheless, at some point, the malignancy may become self-sufficient without needing further contribution of MCs and ST for angiogenesis or matrix degradation. This could explain the lowering of ST levels in deeper MM. Although this is a small series, it may encourage new studies about the role of ST in MM, according also to the number of nevi.