Department of Dermatology, Yamaguchi University Graduate School of Medicine, Ube, Japan
The authors declare no conflict of interest.
To the Editors:
Juvenile xanthogranuloma (JXG) contains cells with a wide variety of morphologic characteristics. Five types of JXG have been described: vacuolated, xanthomatized, scalloped, oncocytic, and spindle cell JXG. Spindle cell xanthogranuloma (SCXG) is a rare variant of JXG characterized by a predominance of spindle-shaped cells. It occurs mainly in adults (20–40 years) and less commonly in children.1 Clinically, SCXG manifests as yellowish to brownish papules and often involves the head, neck, and upper portion of the trunk but may also affect the extremities. Here, we describe an unusual pediatric case of SCXG on the hip presenting as a dark red to bluish nodule with a clinical appearance similar to a Spitz nevus.
A 10-year-old Japanese girl was referred to our department with a 6-month history of a solitary, asymptomatic, and gradually enlarging nodule on the left hip without preceding injury to the area. She was otherwise healthy with an unremarkable medical history. Neither the parents nor the siblings had a history of xanthogranulomas. On physical examination, the nodule was dark red to bluish, 10 × 5 mm in size, firm with an ulcerated center (Fig. 1A). Dermoscopic examination revealed white streaks on a blue background around the periphery of the lesion (Fig. 1B). The results of routine laboratory investigations were within normal limits, including an absence of hyperlipidemia. Our initial diagnosis was a Spitz nevus; an excoriated prurigo nodule would be another possible clinical differential diagnosis. The lesion was surgically removed under local anesthesia several weeks after the initial visit. Histopathological examination of the excised specimen showed dense spindle cell proliferation with a storiform pattern associated with Touton multinucleate giant cells in the dermis (Figs. 2A–C). Extensive hemosiderin deposition was noted in the upper dermis (Figs. 2C and 3A). Neither acanthosis nor hyperpigmentation of the overlying epidermis was present. Immunohistochemically, the lesional cells were strongly positive for CD68 (Fig. 3B) but negative for S100 protein, CD1a, Melan-A, HMB45, c-Kit, CD34, smooth muscle actin, and factor XIIIa. From the clinical and histological findings, we diagnosed the lesion as SCXG. No recurrence was noted at 1-year follow-up.
SCXG is non-Langerhans cell disease (xanthogranuloma family) described by Zelger et al.1 Clinically, SCXG typically occurs in young adults and manifests as a yellow-brown papules affecting—in decreasing frequency—the head, neck, upper trunk, and occasionally, the extremities. Histologically, SCXG is composed predominantly of spindle-shaped cells arranged in a storiform pattern.
Only a handful of cases of solitary SCXGs have been reported2,3 after the initial report by Zelger et al. SCXG may clinically resemble a dermatofibroma (DF). According to Zelger et al, 7 of their 12 cases were initially misdiagnosed as DF/benign fibrous histiocytoma.4 In our case, the initial diagnosis was a Spitz nevus because the lesion was a dark red to bluish nodule, and dermoscopy revealed white streaks on a blue background around the periphery of the lesion. The presence of extensive hemosiderin deposition may have also led to the misdiagnosis. The dermoscopic features of JXG were recently described as a “setting sun” appearance with clouds of pale yellow globules, linear and branched vessels, and a white streak5; these findings were not observed in our case.
The main differential diagnosis of SCXG is DF. The clinical, histological, and immunohistochemical findings of DF are different from SCXG. Clinically, DF is a common benign lesion composed of fibrocytes and macrophages, mostly found on the legs of middle-aged women. Histologically, marked epidermal hyperplasia, prominent peripheral sclerotic bundles of collagen, and occasional peripheral response by lymphocytes and macrophages are observed; moreover, other xanthogranulomatous reactions are absent. Immunohistochemically, DF is positive for factor XIIIa and partially positive for smooth muscle cell antigens, but most lack reactivity for macrophage markers. Although the lesion was similar to DF in some aspects, for example, a typical silhouette, acanthosis, and epidermal hyperpigmentation were lacking and lesional cells were positive for CD68 and negative for factor XIIIa. Therefore, the final diagnosis was SCXG rather than DF. DF and SCXG are sometimes very difficult to differentiate because both are reactive processes—the former is more fibroblastic and the latter with more macrophages.
Based on the histological findings of SCXG, including spindle cells in a storiform pattern and the presence of Touton multinucleate giant cells, progressive nodular histiocytosis should also be considered in the differential diagnosis. Progressive nodular histiocytosis, a disseminated form of non-Langerhans cell disease, typically affects older adults (age range: 40–60 years) on the trunk without concomitant hyperlipidemia. In our case, extensive hemosiderin deposition was noted in the upper dermis, which is an atypical finding in SCXG. In progressive nodular histiocytosis, siderosis is often observed, and this is quite prominent in the rare variant known as xanthosiderohistiocytosis. Therefore, follow-up of the patient is necessary to rule out the possibility of progression of SCXG to progressive nodular histiocytosis.
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3. Kim CR, Kim HJ, Jung MY, et al.. A case of congenital spindle cell xanthogranuloma. Am J Dermatopathol. 2012;34:672–673.
4. Zelger BW, Staudacher C, Orchard G, et al.. Solitary and generalized variants of spindle cell xanthogranuloma (progressive nodular histiocytosis). Histopathology. 1995;27:11–19.
5. Song M, Kim SH, Jung DS, et al.. Structural correlations between dermoscopic and histopathological features of juvenile xanthogranuloma. J Eur Acad Dermatol Venereol. 2011;25:259–263.