# Retrospective Single-Center Case Study of Clinical Variables and the Degree of Actinic Elastosis Associated with Rare Skin Cancers

## TL;DR

This study explores how sun exposure affects rare skin cancers by analyzing tissue changes and patient data.

## Contribution

The study introduces a new method to assess UV exposure's impact on rare skin cancers using a semi-quantitative elastosis grade.

## Key findings

- TEG values were significantly higher in AFX and PDS compared to other rare skin cancers.
- TEG values correlated with age and UV-exposed body sites.
- MCC showed intermediate TEG values, while DFSP and KS had low TEG values.

## Abstract

While sun exposure and associated tissue changes stemming from ultraviolet radiation are closely associated with the most common forms of skin cancer, far less is known regarding rare types of skin cancer. In this study, for the first time, we used a light microscopy technique to evaluate connective tissue changes in samples from patients with six different types of rare skin cancers, assessing the relationship between these changes, patient age, and whether tumors arose on sun-exposed parts of the body. We found that these tissue changes were most pronounced for patients with specific cancers known to be linked to chronic sun damage and tumors arising on sun-exposed parts of the body. We also noted tumor type-specific trends in terms of sex ratios, sites of tumor presentation, and the relationship between the development of particular tumors and patient immunosuppression. Our results are important and novel as they expand the available data associated with these rare skin cancers while also offering insight into the value of differentiating among these tumor types based on their relationship with sun exposure, potentially informing preventative, diagnostic, and/or therapeutic approaches.

(1) Background: Rare skin cancers include epithelial, neuroendocrine, and hematopoietic neoplasias as well as cutaneous sarcomas. Ultraviolet (UV) radiation and sunburns are important drivers for the incidence of certain cutaneous sarcomas; however, the pathogenetic role of UV light is less clear in rare skin cancers compared to keratinocyte cancer and melanoma. In this study, we compared the degree of actinic elastosis (AE) as a surrogate for lifetime UV exposure among selected rare skin cancers (atypical fibroxanthoma [AFX], pleomorphic dermal sarcoma [PDS], dermatofibrosarcoma protuberans [DFSP], Kaposi sarcoma [KS], Merkel cell carcinoma [MCC], and leiomyosarcoma [LMS]) while taking into account relevant clinical variables (age, sex, and body site). (2) Methods: We newly established a semi-quantitative score for the degree of AE ranging from 0 = none to 3 = total loss of elastic fibers (basophilic degeneration) and multiplied it by the perilesional vertical extent (depth), measured histometrically (tumor-associated elastosis grade (TEG)). We matched the TEG of n = 210 rare skin cancers from 210 patients with their clinical variables. (3) Results: TEG values were correlated with age and whether tumors arose on UV-exposed body sites. TEG values were significantly higher in AFX and PDS cases compared to all other analyzed rare skin cancer types. As expected, TEG values were low in DFSP and KS, while MCC cases exhibited intermediate TEG values. (4) Conclusions: High cumulative UV exposure is more strongly associated with AFX/PDS and MCC than with other rare skin cancers. These important results expand the available data associated with rare skin cancers while also offering insight into the value of differentiating among these tumor types based on their relationship with sun exposure, potentially informing preventative, diagnostic and/or therapeutic approaches.