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.

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.

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.

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.

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.

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.

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.

Solitary cutaneous histiocytosis with granular cell changes: a morphological variant of reticulohistiocytoma?

We first report a case of granular cell histiocytosis occurring as a solitary polypoid lesion of the nipple in a 15-year-old girl. Histologically, the lesion was composed of a dermal population of medium- to large-sized, short spindle- to round- to epithelioid-shaped cells with eosinophilic cytoplasm containing numerous and small diastase-resistant periodic acid-Schiff (PAS) positive granules. No associated inflammatory cells were observed. Immunohistochemical studies, revealing immunoreactivity exclusively to vimentin and CD68, were consistent with their histiocytic profile. Based on clinical, morphological and immunohistochemical features, the diagnosis of 'solitary cutaneous histiocytosis with granular cell changes' was proposed. The absence of an inflammatory cell component, such as lymphocytes and leucocytes, along with no history of a previous trauma or medical treatment, suggest that the present lesion could fit into the morphological spectrum of the so-called solitary epithelioid histiocytoma, also known as reticulohistiocytoma. Alternatively, the possibility of a histiocytic reaction to unknown stimuli cannot be completely ruled out. Nevertheless, awareness of solitary cutaneous histiocytosis with granular cell changes is useful to avoid confusion with other dermal tumors, especially 'granular cell tumor' and 'dermal non-neural granular cell tumor'.

Endolymphatic non-langerhans cell histiocytosis of the larynx: report of an uncommon disease manifestation.

We report on an uncommon laryngeal non-Langerhans cell histiocytosis. An 11-year-old boy presented with a 6 months history of progressive breath inhibition. Magnetic resonance imaging showed diffuse laryngeal and local lymph node swelling. Histology first resembled sarcoidosis, however, corticosteroids were ineffective. Lymphoma, infection, immunodeficiency, and autoimmune disease were excluded. Six months later, biopsies were repeated, now showing numerous ectatic lymph vessels with clusters of histiocytes bearing stellate extensions and emperipolesis. S100 protein and CD1a were negative. Indomethacin treatment led to a gradual improvement. In conclusion, we observed a nonmalignant non-Langerhans cell endolymphatic reticulohistiocytosis, not fitting into any of the described categories.

Hereditary progressive mucinous histiocytosis: first report in a male patient.

Progressive mucinous histiocytosis is a very rare, benign, non-Langerhans' cell histiocytosis limited to the skin. In total ten patients (all women) in four families and three sporadic cases have been reported. We report here the first published case of a male patient with progressive mucinous histiocytosis. The multiple red papules on the scalp and forearms were asymptomatic and had slowly increased over approximately the past 20 years. The patient's mother had similar lesions. Histological examination revealed nodules in the dermis with histiocytes and mucin deposition. The histiocytes stained positively with CD31 and negative with CD34, CAM 5.2, PGM-1 and factor XIIIa. Ultrastructurally, the histiocytes showed numerous circular myelin bodies and zebra bodies reminiscent of those seen in lysosomal storage diseases. The genetic transmission of hereditary progressive mucinous histiocytosis remains unclear; we assume an autosomal dominant transmission with some hormonal factor that makes hereditary progressive mucinous histiocytosis more likely in women.

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.

Congenital self-healing reticulohistiocytosis (Hashimoto-Pritzker disease): ten-year experience at Dallas Children's Medical Center.

The real incidence of congenital self-healing reticulohistiocytosis (CSHR) may be underreported because of its high rate of spontaneous resolution and lack of clinical recognition. Currently, there are no criteria other than clinical that can reliably distinguish CSHR from cutaneous involvement by disseminated Langerhans cell histiocytosis (LCH). In this study we investigate the role of E-cadherin, Ki-67, and phosphorylated histone H3 (PHH3) immunohistochemical stains in distinguishing CSHR from disseminated LCH. We found that no significant difference was seen in the histologic features and the expression of E-cadherin, Ki-67, and PHH3 between the two groups; thus supporting the theory that CSHR and LCH represent different ends of a spectrum of the same condition.

Reticulohistiocytosis.

Reticulohistiocytoses consist of a rare group of diseases caused by CD68+ macrophage proliferation. Several advances have been achieved in relation to the receptors involved in these diseases. This knowledge will clarify the physiopathologic mechanisms of the reticulohistiocytoses and direct better therapeutic approaches for patients.