Multiple Cutaneous Reticulohistiocytomas in a Middle-Aged Female.

Sir,

Reticulohistiocytosis is a rare histiocytic proliferative disorder of unknown origin consisting of three main varieties, viz, solitary cutaneous reticulohistiocytoma (CRH), multiple CRH, and multicentric reticulohistiocytosis (MR). We present a case of multiple CRH in a 45-year-old lady, who presented with asymptomatic skin lesions which were slowly increasing in number, of 1 month duration. On examination, there were multiple, firm, nontender, scattered, discrete, skin-colored papules 1–3 mm in diameter over lower part of the face, neck, and trunk [Figure 1a]-c. Possibilities of histoid leprosy, eruptive syringoma, and cutaneous sarcoidosis were considered. There was no peripheral nerve thickening or loss of sensation. Sytemic examination was normal and laboratory parameters were within normal limits. Skin biopsy and microscopic examination of H- and E-stained specimen showed an orthokeratotic epidermis overlying circumscribed aggregates of histiocytic cells with abundant eosinophilic cytoplasm with vesicular nuclei, prominent nucleoli, some with irregular convoluted/grooved nuclei; multinucleated cells admixed with eosinophils, lymphocytes, and few neutrophils in the papillary and reticular dermis [Figure 2a and b]. CD68 staining was positive [Figure 2c] and immunohistochemistry for S 100 was negative [Figure 2d]] in the large cells. All these features were suggestive of CRH. Histiocytoses are generally classified as langerhans cells and nonlangerhans cells. Reticulohistiocytoses (RHC) belongs to the group of nonlangerhans cell histiocytic disorders, which are characterized by the accumulation of histiocytes that do not represent the phenotype of langerhans cells. RHC is characterized by dermal histiocytic infiltration of large, eosinophilic histiocytes with a “glassy” cytoplasm and is divided into three groups: MR, multiple CRH, and solitary CRH.[1]

Figure 1

Multiple, firm, nontender, skin-colored papules over axilla (a), face (b) and abdomen (c)

Figure 2

(a) Dermis showing a circumscribed aggregate of histiocytoid cells (H and E, ×40). (b) Large polygonal cells with abundant eosinophilic cytoplasm, vesicular nuclei and prominent nucleoli admixed with eosinophils (H and E, ×200). (c) CD 68 positive in the tumor cells (×400). (d) S 100 negative in the tumor cells (×400)

Solitary CRH also called epithelioid histiocytoma generally presents as a solitary nodule commonly over the trunk and lower extremities ranging in size from 1.5 to 11 mm. Following removal, they usually do not recur. It has to be differentiated from juvenile xanthogranuloma and Rosai–Dorfman disease.[2] Multiple CRH is characterized by numerous discrete papules and nodules in the absence of systemic involvement. Association with lichen striatus along the lines of Blaschko in a 15-year-old girl has been reported.[3] MR presents with papulo-nodules and a destructive erosive arthritis mimicking rheumatoid arthritis,[4] sometimes associated with connective tissue diseases and internal malignancy in 15–30% of cases. Isolated cases of pulmonary, cardiac, and hepatic involvement have been reported.[5] There may be erythema of skin with soft tissue swelling of the extremities along with clustering of periungual papules called “coral-bead” sign. The histopathology of RHC is characteristic with mononuclear histiocytes, multinucleate giant cells with a ground glass appearance along with spindle-shaped cells and xanthomatized cells. Immunohistochemistry shows dendritic cell lineage with positive staining for CD68 and negativity for S100 and CD1a. Electron microscopy shows absence of Birbeck granules. Dermoscopy shows three typical patterns;[6] a homogeneous pattern with various shades of yellow (defined previously as a “setting-sun” pattern), brown reticular structures, and central white scar-like patches and streaks.

Our patient with multiple CRH was reassured and has been advised to come for follow-up if new lesions or systemic complaints arise.

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