Unusual cutaneous histiocytosis expressing an intermediate immunophenotype between Langerhans' cells and dermal macrophages

Indeterminate cell histiocytosis with naïve cells

“…Despite of absence of cellular atypia and mitosis, the infiltrating cells showed epidermotropism that was reported once in ICH. 6 Unlike the resident epidermal LC, epidermotropic cells were oval in shape surrounded by a clear space and devoid of dendritic cell processes. Additionally, perineural and neural invasion were observed.…”

“…The course of solitary ICH lesions is difficult to assess, because they are usually removed. 6 While most cases of ICH appear spontaneously, there are clues that some may represent reactions to triggers, such as scabies or pityriasis rosea. 7 In these patients, the lesions followed the distribution pattern of the prior disease.…”

“…Total excision, phototherapy, electron beam therapy, chemotherapy, electrodessication, topical pure coal tar, and 5% 5-fluorouracil cream have all been proposed. 24,25 In some patients, the process is clinically benign and may resolve spontaneously. Conservative management might be favorable for these patients.…”

Indeterminate cell histiocytosis successfully treated with phototherapy

“…While some researchers believe that they are precursors of Langerhans cells, which, when en route to the epidermis, remained arrested into the dermis and did not acquire the Birbeck granules, 6 - 8 other researchers believe they are “veiled dendritic cells” that migrate from the skin to the regional lymph nodes. 9 Additionally, experimental evidence points toward the myeloid lineage for the bone-marrow-derived dendritic cells by presenting myeloid lineage markers, such as CD13 and CD33. 10 - 13 …”

“… 15 , 16 Such lesions may be single, a discrete group of lesions, or multiple generalized papules spread over the trunk, face, and extremities, which may present spontaneous remission, stable disease, or remission and recurrence. 4 , 9 , 16 - 18 The exclusive cutaneous presentation is the rule; however, bone and corneal involvement have been reported. 19 , 20 The clinical differential diagnosis of ICH is represented by generalized eruptive histiocytosis, a non-Langerhans cell histiocytosis, but in this condition the histiocytes do not express CD1a and S100 protein.…”