Expression of Potential Dermal Progenitor Cell Markers in the Tumour and Stroma of Skin Adnexal Malignant and Benign Tumours

Challenges in the diagnosis and treatment of the malignant adnexal neoplasms of the head and neck

PURPOSE OF REVIEW

The current review is to present the current knowledge regarding epidemiology, diagnostics, and management of malignant adnexal neoplasms (MANs).

RECENT FINDINGS

Immunotherapy and gene-related therapies are still being developed as the methods of salvage treatment in advanced and disseminated cases: CACNA1S, ATP2A1, RYR1, and MYLK3, as well as p53 or the JAK/STAT pathways, may be therapeutic targets; the efficiency of talimogene laherparepvec and nivolumab is assessed.

SUMMARY

MANs are rare tumors, but due to the aging of population their incidence is increasing. Their clinical presentation is unspecific, which makes the diagnosis challenging. Histopathological assessment is difficult even for experienced pathologists. Mohs micrographic surgery or wide local excision are recommended to treat primary lesions. Adjuvant radiotherapy may be beneficial in case of insufficient or positive surgical margins, in nodal metastases, in selected types of MANs like sebaceous, trichilemmal, and pilomatrix carcinomas, and as the induction treatment in large tumors located in medically fragile or cosmetically important regions. The role of chemotherapy is not well defined; however, it is recommended in distant metastases. Immunotherapy can improve the prognosis in advanced stage of the disease.

Sebaceous immunobiology - skin homeostasis, pathophysiology, coordination of innate immunity and inflammatory response and disease associations

This review presents several aspects of the innovative concept of sebaceous immunobiology, which summarizes the numerous activities of the sebaceous gland including its classical physiological and pathophysiological tasks, namely sebum production and the development of seborrhea and acne. Sebaceous lipids, which represent 90% of the skin surface lipids in adolescents and adults, are markedly involved in the skin barrier function and perifollicular and dermal innate immune processes, leading to inflammatory skin diseases. Innovative experimental techniques using stem cell and sebocyte models have clarified the roles of distinct stem cells in sebaceous gland physiology and sebocyte function control mechanisms. The sebaceous gland represents an integral part of the pilosebaceous unit and its status is connected to hair follicle morphogenesis. Interestingly, professional inflammatory cells contribute to sebocyte differentiation and homeostasis, whereas the regulation of sebaceous gland function by immune cells is antigen-independent. Inflammation is involved in the very earliest differentiation changes of the pilosebaceous unit in acne. Sebocytes behave as potent immune regulators, integrating into the innate immune responses of the skin. Expressing inflammatory mediators, sebocytes also contribute to the polarization of cutaneous T cells towards the Th17 phenotype. In addition, the immune response of the perifollicular infiltrate depends on factors produced by the sebaceous glands, mostly sebaceous lipids. Human sebocytes in vitro express functional pattern recognition receptors, which are likely to interact with bacteria in acne pathogenesis. Sex steroids, peroxisome proliferator-activated receptor ligands, neuropeptides, endocannabinoids and a selective apoptotic process contribute to a complex regulation of sebocyte-induced immunological reaction in numerous acquired and congenital skin diseases, including hair diseases and atopic dermatitis.

Therapeutic Attributes of Endocannabinoid System against Neuro-Inflammatory Autoimmune Disorders

In humans, various sites like cannabinoid receptors (CBR) having a binding affinity with cannabinoids are distributed on the surface of different cell types, where endocannabinoids (ECs) and derivatives of fatty acid can bind. The binding of these substance(s) triggers the activation of specific receptors required for various physiological functions, including pain sensation, memory, and appetite. The ECs and CBR perform multiple functions via the cannabinoid receptor 1 (CB1); cannabinoid receptor 2 (CB2), having a key effect in restraining neurotransmitters and the arrangement of cytokines. The role of cannabinoids in the immune system is illustrated because of their immunosuppressive characteristics. These characteristics include inhibition of leucocyte proliferation, T cells apoptosis, and induction of macrophages along with reduced pro-inflammatory cytokines secretion. The review seeks to discuss the functional relationship between the endocannabinoid system (ECS) and anti-tumor characteristics of cannabinoids in various cancers. The therapeutic potential of cannabinoids for cancer-both in vivo and in vitro clinical trials-has also been highlighted and reported to be effective in mice models in arthritis for the inflammation reduction, neuropathic pain, positive effect in multiple sclerosis and type-1 diabetes mellitus, and found beneficial for treating in various cancers. In human models, such studies are limited; thereby, further research is indispensable in this field to get a conclusive outcome. Therefore, in autoimmune disorders, therapeutic cannabinoids can serve as promising immunosuppressive and anti-fibrotic agents.