"Uncommon Cutaneous Solitary Reticulohistiocytoma: A Case Report"

Ighor Ramon Pallu1*, Pedro Garcia Lemes Proença2, Sofia de Souza Boscoli1, Cintia Prolo3, Juliana Elizabeth Jung4, Mara Rejane Rodrigues Correa Segalla4 and Eduardo Morais De Castro5 1Affiliated to Faculdedes Pequeno Príncipe, Curitiba, Brazil 2Affiliated to Universidade do Extremo Sul Catarinense, Criciúma, Brazil 3Affiliated to Hospital Rio do Testo, Pomerode, Brazil 4Affiliated to Citolab, Curitiba, Brazil 5Affiliated to Citolab & Faculdades Pequeno Príncipe, Curitiba, Brazil


Introduction
The histiocytosis are a group of diseases associated with the exacerbated immune response of macrophages/monocytes. There is still no consensus regarding their morphological classifications and clinical presentations [1,2]. The most common and studied histiocytosis are Langerhans cell histiocytosis and hemophagocytic lymphohistiocytosis. The others are collectively called Non-Langerhans Cell Histiocytosis (NLCH) or rare histiocytosis [3].
Among the NLCH, Reticulohistiocytosis (RH) can present in a multicentric, diffuse cutaneous, or solitary pattern [4,5]. Solitary Reticulohistiocytoma (SRH) presents as a solitary papule or nodule with a reddish or yellowish hue. It affects mainly the skin and mucous membranes, being first described by Zak in 1950 [5][6][7]. SHR is a rare condition, and its prevalence has not yet been established [8]. With this in mind, we present below a rare case of SRH in a female patient from southern Brazil.

Case Report
A female patient, 34 years old, sought medical assistance due to an asymptomatic lesion in the left anterior cervical region, with rapid growth and spontaneous onset six months ago. The patient reported an attempt to remove the lesion because at first, she believed it was acne. Clinical examination identified a yellowish erythematous, with a brownish center, well circumscribed nodule, measuring 1. for the CD68, in addition to a low proliferative index, assessed by ki67 ( Figure 2C). Furthermore, the lesion was negative for CD1A, CD34, and S-100. The morphology and immunohistochemistry, as well as clinical data, were consistent with non-Langerhans cell histiocytosis, favoring reticulohistiocytoma.

Discussion
Although it can be diagnosed in patients of any age, SRH affects mainly young adults, being more prevalent in males, making the case described above even more curious since the disease affected a female patient. [1,3,5,6,9,10]. SRH is a benign, localized disease induced by cytokines that cause a rare non-neoplastic proliferation of skin histiocytes, originated from the lineage of macrophages that react to yet unknown stimuli [4,5]. Clinically, the SRH presents itself as a single, firm, yellowish or reddish, asymptomatic skin nodule, measuring 0.5 to 2.0 centimeters, but usually smaller than one centimeter [1,10]. Its most common location is in the face, followed by neck and trunk, but can also be found in the mucosa.
In our literature review, there are reports of trauma preceding these lesions, which could trigger the local inflammatory response.
However, in most cases, a triggering factor for their development is not identified [1,4,5,10].
The diagnosis is based on the patient's clinical history and the histopathological analysis. The microscopic findings show large histiocytes with eosinophilic cytoplasm in large quantities, with more purplish and amphophilic hues near the center of the histiocyte and lighter eosinophilic staining near the periphery [7]. Immunohistochemistry shows positivity for CD68 and CD163 and, in some cases, also for alpha-1-antitrypsin and lysozyme. The negativity of markers such as CD1a and S100 is essential for the differential diagnosis and exclusion of other histiocytosis [4,11].
Some studies concluded that SRH has clinical, histopathological, and immunohistochemical aspects similar to disseminated xanthogranulomas and multicentric reticulohistiocytosis [12,13].
Since these diseases present worse prognosis than SRH, and may require pharmacological therapy, including chemotherapy, it is essential to exclude these diagnoses. The definitive treatment for SRH consists of total resection of the lesion without the need for adjuvant therapies [1]. contributed to study concept, coordination, supervision, wrote and reviewed the manuscript.