Section 1, chapter 10, tier 2, textual level
Epithelioid Cell Histiocytoma (review of: Silverman JS, Glusac EJ. Epithelioid cell histiocytoma - Histogenetic and kinetics analysis of dermal microvascular unit dendritic cell subpopulations. J Cutan Pathol 2003; 30: 415-422)
This article revived my interest in the 1992 manuscript. I cannot say that the concept of “dermal microvascular unit, comprised of fibroblasts, histiocytes, endothelium, mast cells, and T cells,” is a particularly revealing, or useful, construct in defining a neoplasm. I have trouble with the concept of “fibrovascular dermal mesenchymal tumors” in the characterization of a neoplasm. If CD34+ fibroblasts are representative of “deep dermal dendrocytes,” what is a tumor of such cells doing in the papillary dermis? In the above contribution, the futility of providing morphologic descriptions and interpretations, while using the language of the immunohistochemist, is exposed. Morphology remains a discipline separate from the chemical demonstration of function. The concept of a dendritic system of dermal cells is an outgrowth of this attempt to merge morphology and function. It derives from the notion that dermatofibromas are tumors of factor XIIIa + dendrocytes - hence the designation, dermal dendrocytoma. Later, the overlooked fibroblasts were merely incorporated into the concept of a dermal dendrocytic system by characterizing the fibroblasts as dendritic in outline. In this manner, two cell lines of a “dendritic system” could be accommodated in the concept of dermal dendrocytoma. The old designation, “fibrous histiocytoma,” with modifications to accommodate the functional interdependence of factor XIIIa histiocytes and fibroblasts has at least equal utility. It seems that recently the conflicts in regard to the exact nature of the dermal dendrocyte are avoided by simply making reference to “dendritic cells.”
The above authors describe associations between vessels and the fibroblastic cells; in their selected example, both are CD34 (+). They seem to imply that the fibroblastic cells are progenitors of endothelial cells. Such a relationship would strengthen their proposal that there is a microvascular dermal unit. The reader is asked to cope with “resident microvascular dermal fibroblasts” and “dendritic stromal assembly histiocytes.” The “dermal microvascular unit” is emphasized and, in some manner, the authors imply that the dermal microvascular unit is involved in the formation of epithelioid cell histiocytoma. I suspect that some authors would assign these lesions to a category of “myoperithelioma.”
If the authors examined “epithelioid cell histiocytomas” for collagen, other than type I, they do not include this information in the section on Materials and Methods. They conclude that “epithelioid cell histiocytoma is a “vascular fibrous histiocytoma;” in addition, by their criteria, a representation of all requisite cell types is a feature consistent with an origin from the “dermal microvascular unit.”
In this manuscript, I am uncertain about the relationships between “histiocytoid” cells and “epithelioid” cells. What is a “vascular fibrous histiocytoma?”
Although the language and the functional approach bothers me, it seems that the authors make a case for the epithelioid cells being of fibroblastic nature, and the histiocytic cells being factor XIIIa (+) dendritic histiocytes. These attributes stimulated me in the resurrection of the 1992 manuscript. It seems to me that the authors (Silverman, et al) make a case for a fibroblastic tumor, rich in dendritic histiocytes, but have trouble divorcing themselves from the pliable concept of fibrous histiocytoma. Their abstract identifies the lesion in question as a tumor of proliferating fibroblastic cells with a static population of dendritic histiocytes; by their standards, histiocytoid fibroblastoma might have been a more appropriate designation.
If adventitial myxofibroblastoma is a neoplasm, then one cell type should be identifiable as the neoplastic cell. The plump, fibroblastic cell seems to be the appropriate choice. In neoplasia, function is preserved in relationship to degree of differentiation. For a benign differentiated tumor, cellular relationships tend to recapitulate those of reactive processes involving the same line of cells. That vessels and dendritic histiocytes are resident in adventitial myxofibroblastoma is a measure of differentiation; the relationships do not identify a functional anatomic unit of fibroblasts, vessels, and dendritic histiocytes (i.e., the “dermal microvascular unit”) as the neoplastic precursor.
It appears that socialization, as practiced politically (and imposed on children in public schools), has found its way into pathology in the conceptulization of neoplasia. Tumor cells seem to be losing their identity to a society of cells that function as a unit; all the cells of a tumor, both neoplastic and non-neoplastic cells, become equals.
Angiofibroblastoma of the skin, a recently described lesion (Dias-Cascajo C, Schaefer D, Borghi S: Angiofibroblastoma of the skin. J Cutan Pathol 2002; 29: 534-539), shares location and some histologic features with adventitial myxofibroblastoma. The vascular changes are reminiscent of those seen in AMF. Some of the illustrations present a glomus tumor-like pattern.
I recently found the reviews of AMF. In part, the difficulty in proposing a alternate designation had to do with the fact that the lesion had been accepted by established pathologists as a fibrous histiocytoma. This agreement among pathologists as to the basic nature of the lesion makes an alternate proposal difficult to promote. In addition, the reviewers did not approve of my use of the English language. I suppose my use of the language is a reflection of the way I interpret a lesion; the criticisms indicate that I don’t think properly, at least by journalistic standards. In retrospect, I am not sure whether this is a negative criticism, or a compliment; at the time, I was sufficiently discouraged to just set the material aside.