Title: Generalized multinucleate cell angiohistiocytoma: case report and literature review Running head: Generalized multinucleate cell angiohistiocytoma

Background: Multinucleate cell angiohistiocytoma (MCAH) is an uncommon benign fibrohistiocytic and vascular proliferation, which usually occurs as slow-growing grouped reddish-brown to purple papules and nodules on the distal extremities or face. Patients with generalized MCAH are extremely rare and to our knowledge, there are no more than 11 cases reported previously in the medical literature. Objective: To describe the clinical, histopathologic features and immunohistochemical characteristics of all reported cases of generalized MCAH and investigate any potential clinicopathological correlations. Methods: A systematic review of the literature was done with information collected and organized in a table. A new case report is also described in a 42-year old female with generalized MCAH. Histopathologic and immunohistochemical features of multiple biopsies were analyzed. Results: Men and women are equally affected. It is crucial to take multiple biopsies preferably from newly formed lesions to reach the correct diagnosis. The divergent results in immunohistochemistry staining for CD68 and estrogen receptor (ER) alpha necessitate further studies to reach a precise etiology and pathogenesis and secure it with certainty. Conclusion: Awareness of the clinicopathological hallmarks is important to avoid underdiagnosis of MCAH and the immunohistochemical features may contribute to understanding the pathogenesis of this rare disease. INTRODUCTION Multinucleate cell angiohistiocytoma (MCAH) is a rare mesenchymal skin lesion with less than 150 cases described in the literature.(1) It is characterized by asymptomatic grouped red to This article is protected by copyright. All rights reserved. A cc ep te d A rti cl e violet papules and nodules usually located on the lower extremities and dorsal side of the hands in middle-aged to elderly women. Although the majority of these tumors have been described on the limbs, lesions have also been reported to distribute on the temple,(2) face, eyelids,(3) mucosa,(4) and vermilion of the lips.(5) The arrangement of lesions tends to be solitary, multiple or grouped and shows a tendency to be unilateral. Generalized lesions seem to be the exception. We report herein the clinicopathological features of a retrospective series of 12 generalized MCAH, with a particular focus on their clinical manifestations and the differential diagnosis. Our findings utilizing immunohistochemical techniques are also presented. Report of a patient A 42-year-old female presented to our hospital with an 8-year history of multiple disseminated lesions on her trunk and extremities in September 2015. The lesions began with a few dull-red to brown papules on her trunk which subsequently spread to involve the upper and lower extremities. Asymptomatic, 5 to 15 mm dark red to brown, dome-shaped or flat-topped papules and nodules with a smooth surface were scattered on the trunk, arms, and thighs (Fig. 1.A, B, C and D). They were soft to firm in consistency and were not tender. The lesions developed slowly over several months and finally stopped growing but showed no tendency to resolve. She had no prior history of trauma, insect bites, or scabies, and no history of similar lesions in any family member. Physical examination including neurologic examination was normal. There was no indication of any underlying systemic diseases, and the family history was unremarkable. A routine investigation including blood count, chest x-ray, and abdominal ultrasound did not reveal any abnormality. In the obstetric history, the patient had three abortions before the onset of the lesions and the fourth abortion was in 2013. In recent years, the amount of menstrual blood flow decreased, and her menstruation stopped since half a year ago. The initial clinical impressions This article is protected by copyright. All rights reserved. A cc ep te d A rti cl e were generalized eruptive histiocytosis (GEH), eruptive microvenular hemangioma (MVH), and Kaposi’s sarcoma (KS). Histopathological and Immunohistochemical Features Biopsies were taken from four different lesions where each reflects a different development phase. Firstly, the lesions taken from the abdomen, right shoulder, and the neck, demonstrated a proliferation of small blood vessels together with thickened collagen bundles, and there was a mild perivascular infiltrate of lymphocytes and plasma cells in the dermis. Given that the first three biopsies revealed nonspecific reparative process, a fourth biopsy was taken from a newly formed periumbilical nodule. Microscopic examination of the fourth biopsy revealed a proliferation of small vessels associated with lymphohistiocytic cells and bizarre multinucleated cells in the mid and deep dermis. The later are angulated, star-shaped, and feature up to 10 hyperchromatic nuclei and a basophilic cytoplasm. Unattached melanins and melanophages were found in the superficial dermis. Dilated and ingested blood vessels were conspicuous in the deep dermis. Sparsely distributed mast cells were found nearby the angulated multinucleated cells (Fig. 2.A, B, C, and D). However, there was no hemorrhage; stains for hemosiderin (Perls) were negative. Immunohistochemistry showed that the vascular endothelial cells are positive for antibodies to factor VIII, vimentin, CD31, and CD34, and negative for D2-40, S100, and CD1a. Mononuclear cells express vimentin, CD68, but not S100 or CD1a. MCs were strongly positive for vimentin but negative for CD68 and estrogen receptor (ER) (Fig. 3). A diagnosis of generalized MCAH was made. Consent This study adhered to the tenets of the Declaration of Helsinki. Informed consent was signed by the patient for publication of this report and its related images. This article is protected by copyright. All rights reserved. A cc ep te d A rti cl e Literature review Google Scholar and PubMed were searched for the keyword "generalized multinucleate cell angiohistiocytoma” on June 1, 2016, to identify and assess all cases of generalized MCAH and their relevant citations. We obtained the following data: age, sex, the time before presentation, age at first onset, the site of the lesions, and the histological description of the epidermis, dermis, fibrotic changes, and the immunohistochemical characteristics of all reported cases. Herein, we only included patients with lesions that are considered to be generalized MCAH. Inclusion criteria in the series were: (1) multiple disseminated papules or nodules on the trunk and extremities; (2) presence of bizarre MCs; (3) scattered lymphohistiocytic infiltrate between dermal thickened collagen bundles, and (4) proliferation of blood vessels. To our knowledge, only 11 cases of generalized MCAH have been reported in the literature, including the first case reported in China in 2008. Totally, 12 cases were documented and analyzed in this present study counting our current case, and the results are summarized in Table 1. There were 6 males (50%) and 6 females (50%). The male: female ratio was 1:1. The mean age at diagnosis was 42.75 years (24 to 64 years old). The patients had from tens to hundreds of lesions (our case had 80-100 lesions). The majority of the cases were asymptomatic except for two patients who complained of mild pruritus. None of the patients had any prior history of trauma, insect bites, or scabies. There was no history of any family member with similar lesions. No associated systemic diseases were found in most of the cases that were reported in the literature;(6–10) Except for POEMS syndrome and Castleman's disease, were reported in one patient.(11) Vitiligo with anti-thyroid antibodies in another patient, also anti-Ro 60 and positive antinuclear antibodies were reported once.(12–13) Primary biliary cholangitis, aortic and tricuspid valve replacements following endocarditis, diabetes, and dyslipidemia were associated This article is protected by copyright. All rights reserved. A cc ep te d A rti cl e with MCAH in one patient.(14) Also, the laboratory value of 17-hydroxyprogesterone was elevated in one patient, and gastroesophageal reflux disease was reported in another.(15,16) In our patient, a history of several abortions and early menopause were documented. Discussion MCAH was first identified by Smith and Wilson Jones in 1985.(17) Since then, less than 150 cases, with a marked female predominance (female: male ratio of 3:1), have been reported in the international literature.(1) Clinically, MCAH is characterized by single or multiple, red-brown, or violaceous papules or nodules, measuring 2-15 mm in diameter, usually grouped on an anatomic area, in middle-aged to elderly women. Common sites of involvement included the distal extremities, especially the dorsal side of the hands, wrists, thighs, and legs. Exceptionally, lesions were reported in a generalized distribution. Solitary or multifocal MCAH demonstrates a female predilection (79% cases),(1) but men and women are equally affected in our small series of patients with generalized MCAH. Patients also tend to be young or middle-aged, and had from tens to hundreds of lesions located primarily on the trunk and extremities. Initially, the lesions were discrete, flat-topped, dull-red papules ranging in size from 3 to 15 mm in diameter and slightly tender. The duration of the lesions ranged from 6 months to more than 20 years. During the course of the disease, a few new lesions did develop. 3 out of the 12 patients had concomitant autoimmune-related diseases; this predisposes to a possible immunogenic linkage between MCAH and those diseases. Although this possible link can't be ruled out in certain, we believe that this coexistence along with other systemic diseases seems rather sporadic, given that most of the MCAH cases are free of diseases. The diagnosis of generalized MCAH is based on clinical features and histopathologic examination, which reveals several findings that are not pathognomonic, but that are nevertheless Thi