We studied CD34+ stromal cells/telocytes (CD34+SCs/TCs) in pathologic skin, after briefly examining them in normal conditions. We confirm previous studies by other authors in the normal dermis regarding CD34+SC/TC characteristics and distribution around vessels, nerves and cutaneous annexes, highlighting their practical absence in the papillary dermis and presence in the bulge region of perifollicular groups of very small CD34+ stromal cells. In non-tumoral skin pathology, we studied examples of the principal histologic patterns in which CD34+SCs/TCs have (1) a fundamental pathophysiological role, including (a) fibrosing/sclerosing diseases, such as systemic sclerosis, with loss of CD34+SCs/TCs and presence of stromal cells co-expressing CD34 and αSMA, and (b) metabolic degenerative processes, including basophilic degeneration of collagen, with stromal cells/telocytes in close association with degenerative fibrils, and cutaneous myxoid cysts with spindle-shaped, stellate and bulky vacuolated CD34+ stromal cells, and (2) a secondary reactive role, encompassing dermatitis—e.g., interface (erythema multiforme), acantholytic (pemphigus, Hailey–Hailey disease), lichenoid (lichen planus), subepidermal vesicular (bullous pemphigoid), psoriasiform (psoriasis), granulomatous (granuloma annulare)—vasculitis (leukocytoclastic and lymphocytic vasculitis), folliculitis, perifolliculitis and inflammation of the sweat and sebaceous glands (perifolliculitis and rosacea) and infectious dermatitis (verruca vulgaris). In skin tumor and tumor-like conditions, we studied examples of those in which CD34+ stromal cells are (1) the neoplastic component (dermatofibrosarcoma protuberans, sclerotic fibroma and solitary fibrous tumor), (2) a neoplastic component with varying presentation (fibroepithelial polyp and superficial myxofibrosarcoma) and (3) a reactive component in other tumor/tumor-like cell lines, such as those deriving from vessel periendothelial cells (myopericytoma), epithelial cells (trichoepithelioma, nevus sebaceous of Jadassohn and seborrheic keratosis), Merkel cells (Merkel cell carcinoma), melanocytes (dermal melanocytic nevi) and Schwann cells (neurofibroma and granular cell tumor).

<b><i>Introduction:</i></b> Although Hutchinson’s sign can appear associated with benign conditions, dermoscopic findings of non-melanoma eponychium pigmentation have not yet been described in the literature. We report for the first time to our knowledge the dermoscopic findings of an acral nevus located in the proximal nail fold as well as its clinical-dermoscopic-histologic correlation. <b><i>Case Report:</i></b> A twenty-year-old patient presented with a homogeneous longitudinal melanonychia on the left-hand thumb, with benign dermoscopic pattern, and an irregular, 6-mm, dark-brown hyperpigmented macule on the adjacent eponychium (Hutchinson’s sign). The eponychium lesion showed on dermoscopy two irregular brown-black pigmented blotches, with superimposed parallel brown lines on a brushy distribution, with a thicker terminal end. The histopathologic examination of the proximal nail fold was performed, revealing scattered nevus cells in the epidermal basal layer and dermal-epidermal junction thecae, without any atypia or mitosis. These features were consistent with nevus of the proximal nail fold. <b><i>Discussion:</i></b> Previous descriptions of benign hyponychium’s pigmentations, despite the malignant appearance of the overlying melanonychia, were reported to have a similar dermoscopic pattern, known as longitudinal brushy pigmentation. This newly described dermoscopic sign on the eponychium may help distinguish Hutchinson’s sign related to subungual melanoma to non-melanoma Hutchinson’s sign.

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:We report a case of mycosis fungoides (MF) in an 18-year-old man whose neoplastic T cells expressed CD4, CD8, and CD56, with no evidence of TCR-delta or Epstein–Barr virus (EBER) expression. Clinically, neither hypopigmentation nor hyperpigmentation nor poikilodermatous skin lesions were present, and the lesions subsided with oral corticoids and retinoids and environmental solar ultraviolet exposure. Our case represents the oldest patient reported so far with nonpoikilodermatous, CD8/CD56 MF and adds to the phenotypic diversity of MF in the pediatric population. This distinct phenotype does not seem to be linked to a more aggressive course than the classic CD-4 positive one.