Uncommon cutaneous non-Langerhans cell histiocytosis arising from dermal dendritic cells in adults: a clinicopathological study of five cases.

BACKGROUND: Non-Langerhans cell histiocytosis (non-LCH) is a collective term that encompasses a long list of rare "histiocytosis" that do not meet the criteria for Langerhans cell histiocytosis (LCH). Among cutaneous non-LCH, the xanthogranuloma (XG) family represents a distinct group of disorders derived from dermal dendritic cells (DDCs) at different stages of differentiation. OBJECTIVES: To investigate the clinicopathological characteristics of the XG family in adults and review the relevant literature. MATERIALS AND METHODS: We performed a retrospective clinicopathological study of five adult cases with a previous diagnosis of non-LCH. Clinicopathological features, immunophenotypes, genetic alterations and ultrastructural characteristics were analysed. RESULTS: Skin biopsies revealed that all five cases were characterized by diffuse infiltration of polymorphic cells, which were immunoreactive to factor XIIIa but negative for Langerin, CD1a, and S100. None of the cases harboured the BRAF V600E mutation. Electron microscopy of two cases exhibited abundant cytoplasmic processes with numerous lysosome-like dense bodies and electron-lucent vesicles in the cytoplasm and extracellular matrix. The overall features suggested that DDCs are the cellular origin, and these cases fulfilled the criteria for the XG family. CONCLUSION: The XG family represents a spectrum of rare diseases with different clinical presentations, a wide range of morphological appearances, and a shared common origin (DDCs). This group of disorders has been proposed as a unique entity with diagnostic challenges that should not be underestimated.

Langerhans cell histiocytosis and multiple reticulohistiocytomas in a patient with TAR syndrome: An association not previously described.

We describe a patient with thrombocytopenia-absent radius (TAR) syndrome, multisystemic Langerhans cell histiocytosis and multiple reticulohistiocytomas. A mutational study by massive sequencing identified the Val600Glu (V600E) BRAF mutation in the Langerhans cell histiocytosis lesions, but no molecular alterations were found in the reticulohistiocytoma lesions. The concomitant presence in the same patient of more than one type of histiocytosis from two different groups recognized in the most recent Histiocyte Society classification is an extremely rare event. Our case is the first reported case of multisystemic Langerhans cell histiocytosis and multiple reticulohistiocytomas in a patient with TAR syndrome.

Congenital self-healing reticulohistiocytosis with BRAF V600E mutation in an infant.

Congenital self-healing reticulohistiocytosis (CSHR) is a rare disorder characterized by benign skin lesions with a tendency to self-heal. Multiple skin lesions are usually present in CSHR. It is very difficult to distinguish between CSHR and an invasive Langerhans cell histiocytosis. We present a case of a 5-month-old infant girl who had hypopigmented skin lesions distributed over her neck, thorax and torso. The skin lesions regressed spontaneously 2 months after the diagnosis of CSHR and the child has remained in complete remission without any sign of recurrence over a 2-year follow-up. BRAF V600E mutation was detected in lesional cells along with a low Ki-67 proliferative activity of about 6%. BRAF oncogene-induced senescence might contribute to a mechanism of self-regression in CSHR; however, the exact role of the somatic BRAF V600E mutation in CSHR remains to be determined.

Co-existence of Langerhans cell histiocytosis and reticulohistiocytosis with initial presentation of skull lesions: A case report.

Langerhans cell histiocytosis (LCH) is a rare histiocytic disorder resulting from dysregulated clonal proliferation of Langerhans cells. Reticulohistiocytosis (RH) is another rare histiocytosis caused by the proliferation of histiocytes other than Langerhans cells. Co-existence of LCH and RH in different organs and in the same skin area has not been reported. We present the case of a 20-year-old woman who initially had co-existing bone LCH and cutaneous RH. After 1 year of chemotherapy with cytarabine, bone LCH significantly improved but cutaneous LCH developed in the same area where cutaneous RH was, resulting in hybrid LCH and RH of the skin. This unique history provides some evidence to support the theory that LCH and RH originate from the same stem cells and subsequently develop into hybrid LCH and RH of the skin in a cytokine environment influenced by chemotherapy. Repeat skin biopsies may be considered for adjusting treatment regimens in LCH patients whenever pre-existing skin lesions progress.

Eruptive xanthogranuloma in a healthy adult male.

Xanthogranuloma is a benign, non-Langerhans cell histiocytosis primarily diagnosed in infants and children, although a subset occurs in adults. Multifocal eruptive presentation of xanthogranuloma is very rare with only 4 previous cases reported in the literature to our knowledge. We describe a case of eruptive xanthogranuloma in a 49-year-old man who presented with sudden onset of numerous asymptomatic, red-yellow to orange papules on the face, scalp, axilla, flank and scrotum. Histologic features were consistent with xanthogranuloma with diffuse mixed infiltrate of foamy histiocytes, Touton giant cells and lymphocytes. Other than temporarily elevated non-fasting triglycerides, lab values have been unremarkable including serum plasma electrophoresis; however, the patient will continue to be monitored for ocular and other extracutaneous involvement and hematologic malignancies.

Disseminated intracranial xanthoma disseminatum: a rare case report and review of literature.

BACKGROUND: Xanthoma disseminatum (XD) is a rare benign histiocytic proliferating disease of non-Langerhans cell origin, which is clinically mainly characterized by cutaneous or mucous lesions. Although XD is acknowledged of one systematic disease, involvement of the central nervous system is quite rare. CASE PRESENTATION: We presented one 34-year-old Chinese female with disseminated intracranial XD without cutaneous or oral mucosal papules and masses of the other organs. MR imaging displayed multiple heterogeneous masses with intense enhancement in the right frontal lobe, temporal lobe, corpus callosum, left cuneus, suprasellar region, and right cerebellum. Pathological examination showed a neoplastic lesion composed of plentiful epitheloid or spindle cells. The cell had pink cytoplasm of vacuolation and foam with deviated nucleus absent of atypia and mitosis. The histiocytic markers including CD163, CD11c, Mac387 and CD68 were positive, whereas S-100, CD1a, GFAP, CD21, CD23 and so on were negative immunohistochemically. CONCLUSIONS: Intracranial XD without systemic involvement was extremely rare, which was supposed to be considered in differential diagnosis with other neoplasms of histiocytic origin or gliomas.

Assessment and effective targeting of Interleukin-1 in multicentric reticulohistyocytosis.

Multicentric reticulohistyocytosis (MRH) is a rare multisystemic non-Langerhans histiocytosis characterized by cutaneous nodules and severe destructive polyarthritis, sometimes associated with constitutional symptoms and various organ involvements. Its treatment remains empirical and challenging. We first report herein, the successful treatment of a multicentric reticulohistiocytosis patient with anakinra based on cutaneous biopsy immunostaining and serum cytokines features. A first-line treatment associating methotrexate, cortisone and hydoxychloroquine showed none improvement. Therefore, while further tests were performed to rule out an associated malignancy, auto-immune disease or mycobacterial infection, a treatment with anakinra was chosen instead of anti-TNF-alpha drugs. As soon as the 5th day, anakinra allowed control of fever, then rapid improvement of constitutional symptoms, arthritis, cutaneous lesions, and normalization of C-reactive protein, IL-6, and especially IL-1ß levels. Then methotrexate was added, while anakinra was removed at the 12th month, with persistent and complete remission over the two-year follow up. Further assessment of IL-1 pathogenic role and blockade on larger cohorts of patient could open new therapeutic perspectives for refractory/relapsing MRH, considering the good tolerance profile of specific targeting drugs.

Reticulohistiocytoma of the orbit.

Reticulohistiocytoma is a rare, benign histiocytic proliferation of the skin or soft tissue. While ocular involvement has been documented in the past, there have been no previously reported cases of reticulohistiocytoma of the orbit. In this report, the authors describe a reticulohistiocytoma of the orbit in a middle-aged woman.

S100-Negative, CD1a-Positive Cutaneous Histiocytosis in a Patient with S100-Positive, CD1a-Positive Pulmonary Histiocytosis.

In the diagnostic approach to histiocytic proliferations, immunohistochemistry may be a source of both confusion and clarification. We present a case of a 60-year-old man with a generalized pruritic eruption that demonstrated positive staining for CD1a, but negative staining for langerin and S100 protein. This immunophenotype is neither representative nor characteristic of any recognized dendritic cell tumor but has been previously described in 3 cases of skin-limited histiocytosis. However, our patient also demonstrated pulmonary histiocytic infiltrates that were positive for both CD1a and S100 proteins. This differing expression of S100 protein witnessed in 2 separate organ systems affords us insight into the pathophysiology of these histiocytic proliferations.

Expression of stabilin-1 in M2 macrophages in human granulomatous disease and melanocytic lesions.

Stabilin-1 is an endocytotic scavenger receptor, specifically expressed by non-continuous sinusoidal endothelial cells in the liver, spleen and lymph nodes and by M2 or alternatively activated macrophages in human malignancies. We analysed paraffin-embedded tissue of melanocytic lesions and granulomatous diseases for stabilin-1 expression, using the human/murine RS1 antibody. The specificity of the RS1 staining was confirmed in a knockout model, as only M2-like tumor-associated macrophages and vessels of a B16F10 melanoma in wild type mice stained positive; while staining of tumor-associated macrophages and vessels originating from stabilin-1 deficient mice remained negative for stabilin-1 specific antibody RS1. In human specimens, the RS1 antibody stained tumor-associated macrophages in all pathological stages of melanoma. In addition, five cases of juvenile xanthogranulomas and one case of necrobiotic xanthogranuloma were strongly stabilin-1 positive, while Th-1 cytokine dominated granulomatous diseases such as sarcoidosis and granulomatous leprosy were negative. Stabilin-1 positive vessels were found in all analysed non-Langerhans cell histiocytoses and melanocytic lesions. No stabilin-1 positive vessels were present in any other granulomatous diseases.

Adult-onset reticulohistiocytoma presenting as a solitary asymptomatic red knee nodule: report and review of clinical presentations and immunohistochemistry staining features of reticulohistiocytosis.

Reticulohistiocytomas are benign dermal tumors that usually present as either solitary or multiple, cutaneous nodules. Reticulohistiocytosis can present as solitary or generalized skin tumors or cutaneous lesions with systemic involvement and are potentially associated with internal malignancy. A woman with a solitary red nodule on her knee is described in whom the clinical differential diagnosis included dermatofibroma and amelanotic malignant melanoma. Hematoxylin and eosin staining and immunoperoxidase studies of the biopsy specimen established the diagnosis of adult-onset reticulohistiocytoma (solitary epithelioid histiocytoma). Reticulohistiocytoma is characterized by mononuclear, and occasionally multinuclear, histiocytes with eosinophilic "glassy" cytoplasm. The immunohistochemical profile of a reticulohistiocytoma demonstrates consistent positive expression for CD68 (a marker that is expressed by histiocytes but can also show positive staining in melanomas and carcinomas), CD163 (a very specific marker for histiocytes), and vimentin. Reticulohistiocytomas show variable positive expression for MITF (microphthalmia transcription factor) and S100 protein, both of which are more commonly used as markers for melanocytes. Recurrence of a reticulohistiocytoma is rare, even for patients with an incompletely removed lesion. However, our patient elected to have her residual tumor completely excised.

Reactive granular histiocytosis secondary to arthroplasty prosthesis: a novel reaction pattern.

A reactive histiocytic infiltrate can be seen as an incidental finding in a lymph node biopsy from a patient with a history of joint arthroplasty. We report the case of a 74-year-old female who underwent surgical revision of a polyethylene-based right total knee prosthesis due to chronic wear. At the time of surgery, a soft tissue mass adjacent to the tibial prosthetic insert was noted and excised. Histopathologic examination revealed a sheet-like proliferation of large, histiocytoid cells within the subcutis and superficial fascia. The cells showed abundant eosinophilic, granular cytoplasm and small round bland nuclei. Immunohistochemical evaluation revealed the cells to be positive only for CD68. In addition, abundant PAS-positive cytoplasmic granules were found, and minute particles of polarizable material were noted intracellularly and scattered throughout the interstitium of the infiltrate. These findings were interpreted as consistent with a reactive, non-Langerhans cell histiocytosis secondary to the patient's polyethylene knee prosthesis. This finding appears to be a local correlate of the process previously described in regional lymph nodes as reactive granular histiocytosis. Dermatopathologists should be cognizant of this uncommon reaction pattern to avoid mistaking it for a neoplastic process.