Does subcutaneous cellular tissue exist

BACKGROUND: The definition of the "subcutaneous cellular tissue" is still debated. METHODS: In order to establish the localisation and composition of this tissue, or, merely its existence, we interviewed French dermatologists and conducted a bibliographic study on the historical definitions of the so-called "subcutaneous cellular tissue". A questionnaire was sent to French professors of dermatology to assess their definition of the "subcutaneous cellular tissue". They were also asked to make a simple cartoon showing the anatomy of the skin and "subcutaneous cellular tissue". RESULTS: We obtained 37 answers which could be classified in three main categories: 1) "subcutaneous cellular tissue" and hypodermis are synonymous, 2) "subcutaneous cellular tissue" is an autonomous tissue which separates the hypodermis from the tissues below and 3) "subcutaneous cellular tissue" designates all structures located below the hypodermis. In an historic perspective, the "cellular system" was a macroscopic concept described in the eighteenth century as whitish fibrils delimitating "cells". It was renamed loose connective tissue in the twentieth century and thus "cellular" became obsolete. The definition of skin, and of "subcutaneous cellular tissue" in particular, has greatly changed over time. In the eighteenth century, only epidermis and dermis were considered as belonging to the skin, although some included the tela subcutanea. In the twentieth century, the "subcutaneous cellular tissue" is considered either as a part of the hypodermis, or as the hypodermis itself or as a tissue located between the hypodermis and the fascia. DISCUSSION: The difficulty in defining "subcutaneous cellular tissue" is the result of a French semantic problem. The "cellular tissue" became loose connective tissue. For French dermatologists, the skin is composed of epidermis, dermis and hypodermis and the hypodermis can therefore not be subcutaneous. In order to check whether an autonomous tissue could be evidenced under the skin, we conducted an histologic study, which is presented in a second article.