Journal of Dermatology Research and Skin Care

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Letter to Editor - Journal of Dermatology Research and Skin Care (2017) Volume 1, Issue 1

Solitary reticulohistiocytoma of the skin mimicking amelanotic malignant melanoma

Masatoshi Deguchi*

Department of Dermatology, JR Sendai Hospital, Sendai City, Japan

Corresponding Author:
Masatoshi Deguchi
Department of Dermatology
JR Sendai Hospital
Itsutsubashi 1-1-5
Sendai City
Tel: +81 22-266-9671
E-mail: [email protected]

Accepted Date: November 27, 2017

Citation: Deguchi M. Solitary reticulohistiocytoma of the skin mimicking amelanotic malignant melanoma. Dermatol Res Skin Care. 2017;1(1):15-17

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Letter to the Editor

Solitary Reticulohistiocytoma (SRH) of the skin [1,2] is a benign mesenchymal tumor with histiocytic proliferation of unkown etiology, belonging to reticulohistiocytosis (RH) [3,4]. In contrast to multicentic reticulohistiocytosis (MRH) [1,3,5], the other clinical setting of RH, SRH has no associations with arthritis or systemic lesions. It usually presents an asymptomaic papule or nodule, often sited on the trunk, although any site may be affected. Different from the necessity of systemic therapy for the challenging clinical process of MRH [6,7], the only curative therapy for SRH is surgical removal, or it may even regress over the course on observation. On the other hand, however, it often needs to be distinguished from so many skin tumors including some kind of malignancies [2,3,8]. Among such differential diagnosis, the most important problem is its discrimination from melanoma in view of the unfavorable prognosis for the latter. Here we report a case of SRH mimicking clinical appearance of amelanotic melanoma. A 29-year-old male visited our outpatient office presenting a surface-eroded nodule 7 mm in diameter on his rt. lateral abdomen (Figure 1). He was otherwise healthy. He had had that lesion for 2 month before his visit. Relatively rapid growth of the tumor and its peculiar appearance at the gross level led us to raise amelanotic malignant melanoma as the diagnostic possibility. The pathlogical findings of hematoxylin and eosin stained sections of the excisional biopsy revealed large hematoma just beneath the epidermis, and circumscribed dermal nodule (Figure 2). The nodular lesion was composed of multinucleate epitheloid giant cells with an eosinophilic, glassy appearance-cytoplasm, histiocytes and inflammatory cells mainly by neutrophilic infiltrate (Figure 3). Additional findings include scattered xanthomatized cells. These were histologically pathognomonic characteristics of reticulohistiocytoma. Immunohistochemistry exhibited that such massive distribution of epitheloid histiocytes were immunoreactive for anti-CD68 antibody, in contrast to the negative stains for S-100, HMB-45 and melan-A, allowing distinction from malignant melanoma (Figure 4). Our patient has been disease-free for a year. An asymptomatic skin nodule of subtle appearance should prompt consideration of reticulohistiocytoma in the differential diagnosis.


Figure 1: Clinical appearance of a solitary reticulohistiocytoma in the present patient.


Figure 2: Histological findings from the surgical specimen. (25X).


Figure 3: Characterisic intralesional multinucleate giant cells, histiocytes and inflammatory cells. (200X).


Figure 4: Immunoreactivity of multinucleate ginat cells for CD68. (200X).

Conflict of Interest

The author has nothing to disclose.


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