Pseudolipomatosis cutis.

Abstract

To the Editor: We have read with interest the article by Trotter and Crawford: "Pseudolipomatosis cutis: superficial dermal vacuoles resembling fatty infiltration of the skin" (1). The authors describe 26 of their cases, review the literature, and discuss possible causes of the phenomenon. They conclude that vacuoles have no bearing on the underlying pathologic process and thus are artifacts and comparable to so-called mucosal pseudolipomatosis of the colon described by Snover et al. (2). The authors refer to our paper that appeared in 1986, in which we discuss the histopathologic findings in biopsy specimens from 32 patients with acrodermatitis chronica atrophicans (ACA) (3). In specimens from eight of these patients similar vacuoles in the upper half of the dermis were observed. In 1998 we reported on the histopathologic findings in ACA based on another 111 cases (4). In 11 of these, the presence of vacuoles was striking and in one of them the vacuoles were arranged in a dense band close to the epidermis; also some of the basal cells of the epidermis showed intracellular edema. The vacuoles were seen in a setting of marked inflammatory reaction with inflammatory cell infiltrates and dilated blood vessels and lymphatics. We suggest the possibility that this phenomenon is caused by lymphedema or lymphostasis. Support for this thinking is the knowledge that the dermal lymphatic capillaries arise as blind tubes in the dermal papillae and in the subpapillary dermis link to form the superficial lymphatic plexus. Lymphatic capillaries lack continuous basal lamina and smooth muscle cells, and often have gaps between the endothelial cells; therefore, it is impossible or difficult to identify them with enzyme- or immunohistochemical methods. In addition, resting lymphatic capillaries are collapsed and the endothelial cells are indistinguishable from the connective tissue fibroblasts (5). The results of research made by several groups of investigators indicate that so-called prelymphatics (i.e., channels through the connective tissue leading to capillary lymphatics) exist; they are walled off by ground substance and have no other lining (6). Normally such channels are 30 to 70 nm in radius and number 0.3-1.5/μm2. Injury to the tissues greatly increases their number and dimensions (7). Trotter and Crawford also refer to the article by Lee et al.: "Massive papillary dermal fatty infiltration in a patient with psoriasis" (8). Psoriatic skin has been subjected to close investigation of the microcirculation. The article of Braverman and Yen is informative about the circulation in psoriasis and about the construction of the lymphatic vasculature (9). The psoriatic plaques and the surrounding and clinically normal looking skin contained many dilated lymphatic capillaries, but were most numerous in the plaques. The occurrence of fat cell-like vacuoles in ACA is described earlier and was thought to be caused by fatty degeneration (10), a process not accepted by modern pathologists. In our first series of patients with ACA, frozen material from biopsy specimens with many vacuoles were available for fat staining. Fat was observed only in peripheral nerves and subcutaneous tissue; no vacuoles were seen. This proves that there was no abnormal fat in the dermis, but says nothing about the presence or absence of vacuoles; freezing destroys these delicate structures. We dismiss the possibility of artifacts such as injection of air during administration of local anesthetic or inadequate fixation in our cases: 4-mm punch biopsy specimens were taken by trained persons, immediately fixed in 10% formalin, and transported to the pathology department located in the same building. Eva Brehmer-Andersson, M.D., Ph.D. Anders Hovmark, M.D., Ph.D. Eva Åsbrink, M.D., Ph.D. Departments of Pathology and Dermatology; Södersjukhuset, Stockholm, Sweden