Multicentric Reticulohistiocytosis

Synonyms:

None

Etiology:

Unknown

Associations:

Mutilating osteoarthritis, visceral malignancies

Clinical:

Yellow papules on extremities

Histology:

Aggregations of histiocytes with "ground glass" cytoplasm

IHC repertoire:

CD68+, CD11b+, HAM-56+

Staging:

N/A

Prognosis:

Debilitating arthritis stabilizes

Adverse variables:

Visceral malignancies

Treatment:

Careful screening

Multicentric reticulohistiocytosis is a rare syndrome of adulthood characterized by the rapid appearance of multiple papules and nodules arising in conjunction with a severe, mutilating arthritis. When occurring as part of the syndrome, the reticulohistiocytomas are found on mucosal surfaces in up to 50% of cases (1-2). Visceral reticulohistiocytomas involving lymph nodes, bone marrow, lungs, and endocardium have also been described in patients with the syndrome (3,4). Cardiac involvement may result in cardiac failure in extreme cases. Xanthomatous lesions may also be present. The destructive osteoarthritis tends to be symmetrical and involves primarily the joints in the hands. The knees and wrists are also involved in greater than 50% of cases. The arthritis may precede, occur concurrently with, or follow the appearance of the cutaneous lesions but is the presenting sign in most cases. After a period of rapid deterioration, the arthritis usually stabilizes, but does not improve. In approximately 30% of cases, the constellation of multiple reticulohistiocytomas and destructive osteoarthritis has been associated with visceral malignancies (3,5,6). The types of cancer that have been reported in patients with multicentric reticulohis-tiocytosis are shown in Table 18.1 (7-12). In rare cases, multicentric reticulohistiocytosis has been reported in children, also associated with development of malignancy (9). Resolution of the arthritis has been reported in cases with effective treatment of the underlying neoplasm (13). Systemic vasculitis has also been reported in these patients (5).

Reticulohistiocytoma presents as one or several yellow-brown dermal papules or nodules, occasionally with overlying erythema. In most cases, there are no surface epidermal changes and the growths are most prominent on the dorsal surfaces of the hand, overlying joints (Figure 18.1) (1). The individual lesions are asymptomatic and raise a large clinical differential diagnosis. These lesions occur in adults, with a mean age of 40 years, and there is a slight female predominance. The diagnosis is made ordinarily only following biopsy. These lesions are benign and may resolve spontaneously after an initial period of growth. Affected patients have normal serum lipid levels.

The histologic features of a solitary reticulohistiocy-toma and multicentric reticulohistiocytosis are identical. In either case, the growths demonstrate a compression of the overlying epidermis with a nodular aggregation of large cells within the superficial dermis (Figure 18.2). The aggregate is well-circumscribed, but not encapsulated and is separated from the epidermis by a thin Grenz zone. The histiocytes are large, with abundant eosinophilic cytoplasm and vesicular nuclei. In many cases, the cytoplasm has a characteristic "ground glass" or finely granular appearance. The granules stain with PAS with and without diastase predigestion. Occasional multinucleated cells may be seen, but these are less prevalent than the lipidized Touton giant cells in the similar appearing xanthogranu-loma (Figures 18.2-18.4).

The histiocytes are admixed with lymphocytes and abundant eosinophils in many cases. There is

Table 18.1. Tumors Associated with Multicentric Reticulohistiocytosis

Breast carcinoma Pancreatic adenocarcinoma Squamous cell carcinoma—lung Melanoma

Non-Hodgkin's lymphomas Gastric adenocarcinoma Ovarian mucinous adenocarcinoma Colonic adenocarcinoma Pleural mesothelioma Cervical squamous cell carcinoma

Reticulohistiocytic Granuloma

Figure 18.1. Multiple tan-red papules on digits with periungual accentuation seen in multicentric reticulohistiocytosis.

no tendency to form granulomas and caseation is not seen. Immunostains reveal the histiocytes to express CD68, CD3, CD45, CD11b, and HAM-56 (11). These cells do not express S100 protein, CD1a, or Mac387.

Multicentric reticulohistiocytosis appears, at least in some cases, to be a paraneoplastic phenomenon of unknown pathogenesis. Its recognition warrants a full systemic evaluation in order to screen for possible underlying malignancy and close clinical follow-up (11,12).

Multicentric Reticulohistiocytosis
Figure 18.2. Low power photomicrograph depicting loose aggregates of giant cells with interspersed lymphocytes and neutrophils.

Figure 18.3. Medium power photomicrograph depicting giant cells with surrounding inflammatory cells.

Figure 18.3. Medium power photomicrograph depicting giant cells with surrounding inflammatory cells.

Multicentric Reticulohistiocytosis
Figure 18.4. High power photomicrograph depicting two-toned cytoplasm (ground-glass) with darker periphery with central clearing characteristic of reticulohistiocytosis.
Reticulohistiocytoma

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