Frequency of chronic histological photodage, clinical-pathological variables and cell proliferation index in non-malignant lentigo cutaneous melanoma

Abstract

Cutaneous melanoma (CM) can originate from two main pathways: chronic sun exposure and "nevus pathway". Histologically, the first one shows marked solar elastosis (SE) (mainly in the malignant lentigo (ML) variant), unlike the second one (mild or null), which affects younger patients, with a history of intermittent sun exposure. In-depth analysis of these biological subcategories is important to better understand risk factors, evaluate preventive strategies and contribute to the development of new therapies.

The objective of this investigation was to evaluate the frequency of SE in non-ML CM and describe presentation of clinical-pathological variables and cell proliferation index (CPI).

Descriptive, observational and retrospective study. HNC biopsies archive. Colored sections with H/E and immunostaining with Ki-67. Exclusion criteria: LM variant. Variables: sex, age, histological variant, Breslow, Clark, ulceration, mitosis, vascular invasion, cell morphology, solar elastosis (null, mild, moderate, severe) and CPI (%). Descriptive statistics.

Of 36 patients, 50% were men and 50% women. Average age: 60.2 years (26-86). Variants: 26 cases (72%) nodular, 5 superficial spreading (14%), 3 acrolentiginous (8%), 1 nevoid (3%) and 1 balloon cell (3%). Average Breslow: 4.9 mm (1.5-15 mm). 26 (72.2%) Clark IV and 10 (27.8%) Clark V. 22 (61.1%) ulcerated. 3 (8.3%) with vascular invasion. 29 (80.6%) with epitheloid cells, 6 (16.7%) with fusiform cells and 1 (2.7%) mixed. Solar elastosis: null in 13 cases (36.1%), mild in 15 (41.7%), moderate in 7 (19.4%) and severe  in 1 (2.7%). Average CPI: 15% (1-50%). No histological remnant of nevi was found in any case.

The majority of cases were nodular melanomas with mild or no SE. The presence of SE in moderate and severe intensity in several cases (19.4% and 2.7%) could indicate that chronic sun exposure also plays a role in oncogenesis in addition to the “nevus pathway” in non-ML CM, which would highlight the importance of adequate sun protection not only in summer but also daily especially in low phototypes, as a preventive action, in addition to periodic control of melanocytic nevi.