Background:  Lymphedema typically affects a whole limb. Rarely, lymphedema can present as a circumscribed plaque or an isolated skin tumor. Objective:  To describe the clinical and pathologic characteristics and etiologic factors of localized lymphedema. Methods:  Case–control study of skin biopsy and excision specimens histologically diagnosed with lymphedema and presenting as a localized skin tumor identified during a 4‐year period. Results:  We identified 24 cases of localized lymphedema presenting as solitary large polyps (11), solid or papillomatous plaques (7), pendulous swellings (4), or tumors mimicking sarcoma (2). Patients were 18 females and 6 males with a mean age of 41 years (range 16–74). Anogenital involvement was most frequent (75%) – mostly vulva (58%), followed by eyelid (13%), thigh (8%) and breast (4%). Causative factors included injury due to trauma, surgery or childbirth (54%), chronic inflammatory disease (rosacea, Crohn’s disease) (8%), and bacterial cellulitis (12%). Eighty‐five percent of these patients were either overweight (50%) or obese (35%). Compared with a series of 80 patients with diffuse lymphedema, localized lymphedema patients were significantly younger (41 vs. 62 years old, p = 0.0001), had no history of cancer treatment (0% vs. 18%, p = 0.03), and had an injury to the affected site (54% vs. 6%, p = 0.0001). Histologically, all cases exhibited dermal edema, fibroplasia, dilated lymphatic vessels, uniformly distributed stromal cells and varying degrees of papillated epidermal hyperplasia, inflammatory infiltrates and hyperkeratosis. Tumor size significantly and positively correlated with history of cellulitis, obesity, dense inflammatory infiltrates containing abundant plasma cells, and lymphoid follicles (p < 0.05). A history of cellulitis, morbid obesity, lymphoid follicles and follicular cysts predicted recurrent or progressive swelling despite excision (p < 0.05). Conclusions:  Localized lymphedema should be considered in the etiology of skin tumors when assessing a polyp, plaque, swelling or mass showing dermal edema, fibrosis and dilated lymphatics on biopsy. A combination of lymph stasis promoting factors (trauma, obesity, infection and/or inflammatory disorders) produces localized elephantiasis.

Background Melastatin (TRPM1), a.k.a. transient receptor potential cation channel, subfamily M, member 1 (TRPM-1) regulates melanocyte differentiation and proliferation. TRPM1 is transcriptionally regulated by the essential melanocyte transcription factor MITF (microphthalmia-associated transcription factor). For the most part, MITF expression is preserved during melanoma progression, while TRPM1 mRNA expression decreases or is completely lost. The loss of TRPM1 is associated with melanomas that are more aggressive. Objective To assess the relationship between TRPM1 mRNA expression and the expression of MITF and nine other markers of melanocytes and melanin-related proteins by immunohistochemistry in normal skin, scars, hair follicles and ordinary melanocytic nevi. Methods Samples of normal skin (n = 102; from tumor excisions and plastic procedures), scars (n = 5; from re-excision specimens) and compound melanocytic nevi (n = 4) were evaluated for the presence of TRPM1 mRNA transcripts as detected by chromogenic in situ hybridization (CISH). Immunohistochemical techniques were used to detect melanin-related proteins including: MITF, S100 protein, Mart-1, tyrosinase, Mel5, HMB45, tyrosinase-related protein-1 (TRP1), TRP2 and α-melanocyte stimulating hormone (αMSH). The labeling index (LI) was defined as the number of intraepidermal cells expressing mRNA or protein per one hundred basal keratinocytes. Results A wide range of LI was found for all markers (0–33 positive cells/100 keratinocytes). When these LI were compared, no significant differences in the expression of MITF, S100, Mart1, tyrosinase proteins and TRPM1 mRNA were identified. The LI for TRPM1 mRNA expression ranged from 74% of that for MITF to 86% for tyrosinase. The LI for TRP-1, TRP-2 and Mel5 was similar to that of TRPM1, while HMB-45 had a significantly lower LI than all other markers. TRPM1 mRNA correlated most tightly with MITF and tyrosinase expression (r = 0.81 and 0.68, respectively, both p = 0.0001). Likewise, the strongest correlation among all the melanin-related proteins existed between tyrosinase and MITF (r = 0.79, p = 0.0001). There was variable expression of melanin-related proteins when LI were analyzed by anatomic site, patient age, extent of sun-damage and proximity to a melanocytic tumor. Anogenital skin showed the highest and acral skin the lowest LI for TRPM1, MITF, S100 protein, Tyrosinase, Mel5 and HMB45. Advanced age (>60 years) was associated with decreased TRPM1 expression. Sun-damaged skin exhibited significantly increased LI as measured by MITF, S100 protein, Mart1, tyrosinase and HMB-45, but no differences for TRPM1. However, the MITF-TRPM1 differential (i.e. MITF LI-TRPM1 LI = MITF+TRPM1 – melanocytes) was significantly increased in site-matched skin (4.6 ± 4.4 vs. 1.5 ± 2.5, p = 0.01). There was a suggestion of reduced LI in normal skin in the proximity of melanoma (from melanoma re-excision specimens) for S100, HMB45 and TRPM1 mRNA. TRPM1 LI was significantly decreased in scars compared to normal skin (5.6 ± 1....

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