Synchronous occurrence of primary cutaneous B-cell lymphoma and cutaneous Rosai-Dorfman disease in distinct lesions: A unique association.

Rosai-Dorfman disease, also known as sinus histiocytosis with massive lymphadenopathy (SHML), is a rare subtype of reactive histiocytosis which is seldom associated with Hodgkin's and non-Hodgkin's lymphomas. To date, the coexistence in the same patient of extra nodal SHML and primary cutaneous B-cell lymphoma (PCBCL) has been reported in the literature, as metachronous diagnosis in the anatomical area of the original PCBCL or synchronous occurrence in the same lesions. However, no data have been published as for synchronous occurrence of the two pathological entities in distinct anatomical sites. Herein, we report the first ever described synchronous occurrence of PCBCL and SHML, detected in distinct lesions, affecting the same patient. The complete resolution of the patient's PCBCL after rituximab treatment and the concomitant regression of SHML suggest that this clinically benign reactive histiocytic proliferation, potentially triggered by the lymphoma microenvironment itself, may take place not only in the site of the PCBCL lesion, but also in other distant areas not directly affected by the primary cutaneous lymphoma.

A rare presentation of Rosai-Dorfman-Destombes disease with central nervous system involvement and cutaneous wounds.

OBJECTIVE: The aim of this case report is to investigate an uncommon presentation of Rosai-Dorfman-Destombes (RDD) disease, and discuss possible differential diagnoses and treatment options for this pathology. RDD is a rare disorder of histiocytes that typically presents in patients as painless cervical lymphadenopathy. However, this case involves a patient with the central nervous system (CNS) type of RDD who later developed cutaneous lesions. METHOD: Several differential diagnoses were examined, including hidradenitis suppurativa, pilonidal cyst and pressure ulcers. It is important to be able to exclude these diagnoses based on the presentation, patient demographic and wound location. RESULTS: Biopsies verified the presence of RDD in the patient's suprasellar hypothalamic mass and skin lesions, confirming the patient had both CNS-RDD and cutaneous-RDD in the absence of lymphadenopathy. CONCLUSION: Recognising the unique manifestations of rare diseases such as RDD prevents delay of proper intervention and treatment.

Unifocal Type-3 Mixed Histiocytosis in a 10-Years Old Child.

BACKGROUND: Histiocytoses patients present with highly heterogeneous clinical and histopathological pictures requiring multidisciplinary management. Mixed histiocytosis is a recently described group of syndromes defined by the histological overlap of Langerhans cell histiocytosis and other histiocytic proliferations that include three clinically and prognostically different conditions (i.e., Type-1-3 mixed histiocytosis). CASE REPORT: We describe a 10 year-old boy with unifocal (type-3) mixed histiocytosis - Langerhans cell histiocytosis combined with a lesion with features intermediate between Rosai-Dorfman disease and reticulohistiocytosis. Sixty months after excision, the child is disease free. DISCUSSION: Cutaneous type-3 mixed histiocytosis (Langerhans cell histiocytosis with Rosai-Dorfman disease/reticulohistiocytosis) may occur in older childhood, be unifocal, and be cured by surgical excision.

Benign but fatal: management of endotracheal Rosai-Dorfman disease with acute onset.

Rosai-Dorfman disease (RDD) is a non-malignant condition mainly manifesting as a proliferation of histiocytes in lymph nodes. Endotracheal RDD (ERDD) with an acute onset presentation is extremely rare. There are few case reports of ERDD mainly concerning its pathology, diagnostics and bronchoscopic treatment, without providing sufficient clinical information from a comprehensive perspective. As a novel and challenging technique, tracheal resection and reconstruction (TRR) with spontaneous-ventilation video-assisted thoracoscopic surgery (SV-VATS) has been reported as feasible and safe in highly selected patients, but few centres have shared their experience with this approach. This case-based discussion includes not only practical issues in the management of a life-threatening ERDD patient, but also specialists' views on the management of acute obstructive airway, and the surgeons' reflection on TRR with SV-VATS.

PU.1 is a useful nuclear marker to distinguish between histiocytosis and histiocyte-rich tumours.

AIMS: The aim was to test the expression of PU.1 on different types of histiocytoses and to test the utility of PU.1 in confirming or excluding a histiocytic origin in tumour samples with suspicion of histiocytosis. METHODS AND RESULTS: We analysed 66 biopsies of nonmalignant histiocytoses represented by Langerhans-cell histiocytosis (n = 13), Erdheim-Chester disease (ECD) (n = 19), Rosai-Dorfman disease (RDD) (n = 14), mixed ECD-RDD (n = 3), ALK-positive histiocytosis (n = 6), and juvenile xanthogranuloma (n = 11). All cases were positive for PU.1 in reactive and neoplastic histiocytes. In addition, 39 cases of tumours with high-grade cytological atypia were referred to our center as suspicion of malignant histiocytosis/histiocytic sarcoma and only 18 were confirmed. Indeed, more than half of these tumours (21/39) were either undifferentiated malignant tumours with a stroma rich in histiocytes, diffuse large B-cell lymphoma, or high-grade dedifferentiated liposarcoma. PU.1 was useful to distinguish between the negativity of large atypical nuclei and the positivity of stromal reactive histiocytes. CONCLUSION: PU.1 is expressed by all types of histiocytosis. It distinguishes histiocytosis from histiocyte-rich tumours with an easy interpretation due to its sharp nuclear staining. Its negativity in lesional/tumour cells in histiocyte-like lesions is useful to eliminate a histiocytosis.

Characterizing Rosai-Dorfman disease with [18F]FDG PET/CT: a retrospective analysis of a single-center study.

OBJECTIVES: Rosai-Dorfman disease (RDD) is a rare non-Langerhans cell histiocytic proliferative disorder. We performed a retrospective study to characterize the clinical and [18F]FDG PET/CT features of RDD. METHODS: We retrospectively recruited 38 RDD patients with [18F]FDG PET/CT scan in our center. [18F]FDG PET/CT features were assessed, and clinical and follow-up data were recorded. RESULTS: In the recruited patients, 20/38 (52.6%) patients had single-system disease, while others (18/38, 47.4%) had disease affecting multiple system. RDD most commonly involved the upper respiratory tract (47.4%), followed by cutaneous/subcutaneous lesion (39.5%), lymph node (36.8%), bone (31.6%), central nervous system (28.9%), and cardiovascular system (13.2%) in the recruited patients. In PET/CT, the RDD lesions were FDG-avid, and the SUVmax of the hottest lesion in an individual patient was positively correlated with C-reactive protein levels (r = 0.418, p = 0.014), and negatively correlated with hemoglobin levels (r = -0.359, p = 0.036). The overall response rate of the first-line treatment was 80.8% in newly diagnosed RDD patients, and for patients with relapsed/progressive RDD, the overall response rate was 72.7%. CONCLUSION: [18F]FDG PET/CT could be a useful tool for evaluating RDD. KEY POINTS: • About half of the patients with Rosai-Dorfman disease had single-system disease, while others had disease affecting multiple system. Rosai-Dorfman disease most commonly involved the upper respiratory tract, followed by cutaneous/subcutaneous lesion, lymph node, bone, central nervous system, and cardiovascular system. • In [18F]FDG PET/CT, Rosai-Dorfman disease was usually hypermetabolic, and the SUVmax of the hottest lesion in an individual patient was positively correlated with C-reactive protein levels. • Rosai-Dorfman disease usually has a high overall response rate after treatment.

Comparison of neuroimaging features of histiocytic neoplasms with central nervous system involvement: a retrospective study of 121 adult patients.

OBJECTIVES: To compare neuroimaging characteristics of three types of histiocytoses, namely Langerhans cell histiocytosis (LCH), Erdheim-Chester disease (ECD), and Rosai-Dorfman disease (RDD), with central nervous system (CNS) involvement. METHODS: A total of 121 adult patients with histiocytoses (77 LCH, 37 ECD, and 7 RDD) and CNS involvement were retrospectively included. Histiocytoses were diagnosed based on histopathological findings combined with suggestive clinical and imaging features. Brain and dedicated pituitary MRIs were systematically analyzed for tumorous, vascular, degenerative lesions, sinus, and orbital involvement and for hypothalamic pituitary axis involvement. RESULTS: Endocrine disorders, including diabetes insipidus and central hypogonadism, were more common in LCH patients than in ECD and RDD patients (p < 0.001). In LCH, tumorous lesions were mostly solitary (85.7%), located in the hypothalamic pituitary region (92.9%), and without peritumoral edema (92.9%), while in ECD and RDD, tumorous lesions were often multiple (ECD: 81.3%, RDD: 85.7%), their distribution was more widespread with meninges mostly involved (ECD: 75%, RDD: 71.4%), and they most likely presented with peritumoral edema (ECD: 50%, RDD: 57.1%; all p ≤ 0.020). Vascular involvement was an exclusive imaging characteristic of ECD (17.2%), which was not observed in LCH or RDD; this was also associated with a higher risk of death (p = 0.013, hazard ratio = 11.09). CONCLUSION: The typical characteristic of adult CNS-LCH was endocrine disorders with radiological findings limited to the hypothalamic pituitary axis. The pattern of multiple tumorous lesions with predominant involvement of meninges was the main manifestation of CNS-ECD and CNS-RDD, while vascular involvement was pathognomonic for ECD and associated with poor prognosis. CLINICAL RELEVANCE STATEMENT: Involvement of the hypothalamic-pituitary axis is the typical imaging characteristic of Langerhans cell histiocytosis. Multiple tumorous lesions, predominantly involving but not limited to meninges, occur in most Erdheim-Chester disease and Rosai-Dorfman disease patients. Vascular involvement occurs only in Erdheim-Chester disease patients. KEY POINTS: • The different distribution patterns of brain tumorous lesions can help differentiate among LCH, ECD, and RDD. • Vascular involvement was an exclusive imaging finding of ECD and was associated with high mortality. • Some cases with atypical imaging manifestations were reported to further expand the knowledge on these diseases.

The clinical importance of the host anti-tumour reaction patterns in regional tumour draining lymph nodes in patients with locally advanced resectable gastric cancer: a systematic review and meta-analysis.

BACKGROUND: The status of regional tumour draining lymph nodes (LN) is crucial for prognostic evaluation in gastric cancer (GaC) patients. Changes in lymph node microarchitecture, such as follicular hyperplasia (FH), sinus histiocytosis (SH), or paracortical hyperplasia (PH), may be triggered by the anti-tumour immune response. However, the prognostic value of these changes in GaC patients is unclear. METHODS: A systematic search in multiple databases was conducted to identify studies on the prognostic value of microarchitecture changes in regional tumour-negative and tumour-positive LNs measured on histopathological slides. Since the number of GaC publications was very limited, the search was subsequently expanded to include junctional and oesophageal cancer (OeC). RESULTS: A total of 28 articles (17 gastric cancer, 11 oesophageal cancer) met the inclusion criteria, analyzing 26,503 lymph nodes from 3711 GaC and 1912 OeC patients. The studies described eight different types of lymph node microarchitecture changes, categorized into three patterns: hyperplasia (SH, FH, PH), cell-specific infiltration (dendritic cells, T cells, neutrophils, macrophages), and differential gene expression. Meta-analysis of five GaC studies showed a positive association between SH in tumour-negative lymph nodes and better 5-year overall survival. Pooled risk ratios for all LNs showed increased 5-year overall survival for the presence of SH and PH. CONCLUSIONS: This systematic review suggests that sinus histiocytosis and paracortical hyperplasia in regional tumour-negative lymph nodes may provide additional prognostic information for gastric and oesophageal cancer patients. Further studies are needed to better understand the lymph node reaction patterns and explore their impact of chemotherapy treatment and immunotherapy efficacy.

Neurological Manifestations of Histiocytic Disorders.

PURPOSE OF REVIEW: Histiocytic disorders, including Erdheim-Chester disease (ECD), Langerhans cell histiocytosis (LCH), and Rosai-Dorfman disease (RDD), are rare neoplasms that may present with a spectrum of neurologic involvement. Diagnostic delay is common due to heterogeneity in presentation and challenging pathology. RECENT FINDINGS: Recent advances in the treatment of these diseases targeted towards mutations in the MAP kinase pathway have led to an improved prognosis in these patients with neurologic involvement. It is critical for clinicians to have a high index of suspicion to allow for early targeted treatment and optimize neurologic outcomes. A systematic approach to diagnosis is presented in this article to allow for accurate diagnosis of these rare diseases.

Histiocytoid melanoma: Diagnostic pitfall and mimicker of non-Langerhans cell histiocytoses including reticulohistiocytoma.

Melanoma and benign histiocytic proliferations can sometimes show considerable clinical and histopathologic overlap. Recently, cases of melanomas resembling xanthogranuloma and Rosai-Dorfman disease have been reported, and herein we report a case of melanoma closely mimicking reticulohistiocytoma. An 84-year-old man presented with a 1 cm purple-red nodule on his arm concerning for squamous cell carcinoma. While the biopsy findings resembled reticulohistiocytoma, the clinical context and regression changes at the lesion perimeter raised stronger concern for melanoma, which was confirmed with immunohistochemistry. We review prior rare reports of melanomas resembling non-Langerhans cell histiocytic proliferations and summarize helpful clinical and histopathologic clues to avoid a diagnostic pitfall when confronted with this unusual quandary.

A unique case of isolated thoracic spinal Rosai-Dorfman disease related to IgG4.

Rosai-Dorfman disease (RDD) is a rare benign histiocytosis usually characterized by massive cervical lymphadenopathy and systemic manifestations. Extranodal, especially spinal involvement, is extremely rare. Our case was deemed worthy of presentation because it was the first reported isolated case of spinal RDD related to IgG4 and mimicked meningioma clinically and radiologically. A case with an intradural extramedullary mass causing neurological compression findings in the thoracic spinal region and radiologically mimicking meningioma is presented. In the histomorphological examination of the resection material, polymorphonuclear leukocytes in the dura, histiocytes showing emperipolesis, an increase in collagenized fibrous connective tissue, and intense lymphoplasmacytic cell infiltration accompanied by obliterative phlebitis were observed. Immunohistochemically, the histiocytic cells were found to be S-100 protein, CD68, and CD163 positive and CD1a and langerin negative, and more than half of the plasma cells were immunoglobulin-G4 (IgG4) positive. Although rare, RDD or IgG4-related meningeal disease should be considered in the differential diagnosis of dural-based spinal masses that radiologically suggest meningioma. The pathologist should be aware that these two histopathological entities may coexist. To our knowledge, this is the first case of "isolated spinal RDD related to IgG4" reported in the literature.

Primary diffuse Rosai-Dorfman disease in central airway: a case report and literature review.

BACKGROUND: Rosai-Dorfman disease (RDD) is a rare benign non-langerhans cell histiocytosis, mainly involving lymph nodes and skin. It is even rarer occurring only in central airway of lung and in diffuse form. Central airway RDD is similar to malignant tumor in imaging by radiological method and in bronchoscopy features. It is difficult to differentiate it from primary airway malignant tumor and to diagnose correctively in time. CASE PRESENTATION: Here we present a rare case of 18-year-old male diagnosed with primary diffuse RDD in central airway. Although the features examined by enhanced chest computed tomography, positron emission tomography/computed tomography, diffusion-weighted imaging of enhanced chest MRI and bronchoscopy indicate to be malignant tumor, the patient was definitely confirmed by multiple transbronchial biopsies and immunohistochemistry. After two transbronchial resections, the patient's symptoms of paroxysmal cough, whistle sound and shortness of breath were significantly reduced, as well as the airway stenosis was significantly improved. After 5 months of follow-up, the patient had no symptoms and the central airway were unobstructed. CONCLUSIONS: Primary diffuse RDD in central airway is characterized by intratracheal neoplasm, which is usually suspected as malignant tumor according to radiological image and bronchoscopy. Pathology and immunohistochemistry are necessary for definite diagnosis. Transbronchial resection is effective and safe for patients with primary diffuse RDD in central airway.

Early recurrence of Rosai-Doefman disease after total removal resection: a case report.

BACKGROUND: Rosai-Dorfman disease (RDD) involving the central nervous system (CNS) is rare and observed in 5% of all patients with extranodal RDD. According to a previous report, gross total resection is curative; however, we encountered a case of recurrence following gross total resection. We discuss our case and review previous reports on recurrent RDD. CASE DESCRIPTION: A 68-year-old woman came to the hospital complaining of left parietal mass. A tumor that had partially eroded the frontal bone was found. As the lesion was suspected to be malignant, we performed a total resection. Pathology results were indicative of an RDD. We did not prescribe adjuvant therapy because total resection was performed. However, after a year, abnormal accumulation in the left parietal bone was observed on FDG-PET. This was considered as recurrence, and re-excision was performed. Pathological assessments confirmed the recurrence of RDD. CONCLUSIONS: Our case demonstrated the recurrence of RDD following total resection. Future reports should assess these peculiarities. This will facilitate discussions on the risk factors and the effectiveness of treatment methods.

Rosai-Dorfman disease mimicking cavernous hemangioma: a case report.

A 31-year-old female presented to the clinic with a 2 year history of proptosis of the right eye. She was diagnosed with cavernous hemangioma during her initial ophthalmologic consult and was advised monitoring. However, after a considerable increase in proptosis, she underwent an excision biopsy of the right orbital mass. A diagnosis of Rosai Dorfman disease was made after the histopathology report revealed a fibrosclerotic tissue with histiocytic proliferation showing emperipolesis that is mixed with numerous small lymphocytes and plasma cells. Rosai Dorfman disease is a rare disease presenting with lymphadenopathy and sinus histiocytosis. Orbital involvement can be the principal manifestation with proptosis as the most common presentation. Resection of the orbital lesion helped in the resolution of the mild ophthalmic symptoms but since the disease has other systemic associations, a complete systemic workup should be done to monitor recurrence.

Limited sinonasal Rosai-Dorfman disease presenting as chronic sinusitis.

AIMS: The sinonasal tract is a common extranodal site for Rosai-Dorfman disease (RDD). Recently, histiocytes with features of RDD were identified in the clinical setting of chronic sinusitis. This study evaluates whether this phenomenon should be considered part of the RDD spectrum or classified separately as RDD-like histiocytes. METHODS AND RESULTS: We prospectively collected 13 cases showing histological features of RDD in chronic sinusitis patients and identified 14 with similar findings (3.5%) via retrospective review of 403 sinus contents over 2 years. All 27 cases displayed nodular aggregates of eosinophilic histiocytes with intermixed lymphoplasmacytic inflammation, prominent eosinophils and emperipolesis. The histiocytes were positive for S100 protein and cyclin D1 and negative for CD1a and CD207. All patients presented with severe chronic sinusitis without tumour formation or systemic symptoms. Twelve patients with follow-up (55%) required repeat sinus surgery compared with just 43 other sinusitis patients evaluated (11%); features of RDD were present in their additional specimens. Two cases that underwent targeted next-generation sequencing (20%) had oncogenic mutations in NF1 and KEAP1. CONCLUSIONS: Overall, these findings confirm diagnostic histological and immunohistochemical features of RDD in a subset of chronic sinusitis specimens. While patients uniformly lack systemic involvement or tumefactive growth, they have a high risk of recurrent sinus disease. Although the relatively subtle nature of the findings raises consideration of separate classification, the presence of occasional oncogenic mutations and evidence of consistent MAPK/ERK pathway activation via cyclin D1 positivity suggests that this phenomenon represents a unique limited manifestation of RDD.

Phenotypic intrafamilial variability including H syndrome and Rosai-Dorfman disease associated with the same c.1088G > A mutation in the SLC29A3 gene.

BACKGROUND: Mutations in the SLC29A3 gene, which encodes the nucleoside transporter hENT3, have been implicated in syndromic forms of histiocytosis including H syndrome, pigmented hypertrichosis with insulin-dependent diabetes, Faisalabad histiocytosis and Familial Rosai-Dorfman disease (RDD). Herein, we report five new patients from a single family who present with phenotypes that associate features of H syndrome and Familial Rosai-Dorfman disease. METHODS: We investigated the clinical, biochemical, histopathological and molecular findings in five Tunisian family members' diagnosed with Familial RDD and/or H syndrome. The solute carrier family 29 (nucleoside transporters), member 3 (SLC29A3) gene was screened for molecular diagnosis using direct Sanger sequencing. RESULTS: Genetic analysis of all affected individuals revealed a previously reported missense mutation c.1088 G > A [p.Arg363Gln] in exon 6 of the SLC29A3 gene. Four affected members presented with clinical features consistent with the classical H syndrome phenotype. While their cousin's features were in keeping with Familial Rosai-Dorfman disease diagnosis with a previously undescribed cutaneous RDD presenting as erythematous nodular plaques on the face. This report underlines the clinical variability of SLC29A3 disorders even with an identical mutation in the same family. CONCLUSION: We report a rare event of 5 Tunisian family members' found to be homozygous for SLC29A3 gene mutations but showing a different phenotype severity. Our study reveals that despite a single mutation, the clinical expression of the SLC29A3 disorders may be significantly heterogeneous suggesting a poor genotype-phenotype correlation for the disease.

A case of histiocytoid angiosarcoma mimicking Rosai-Dorfman disease histopathologically.

There are very few documented cases of histiocytoid angiosarcoma in the literature. We report a rare case of histiocytoid angiosarcoma demonstrating emperipolesis, a histopathologic finding that mimics Rosai-Dorfman disease (RDD). A 77-year-old male presented with a subcutaneous nodule on his left forehead. Microscopic examination of the tumor revealed a dense lymphohistiocytic and plasmacytic infiltrate with large epithelioid cells, many of which showed abundant pale eosinophilic to foamy-appearing cytoplasm, and some of which displayed phagocytosis of intact inflammatory cells and erythrocytes. The tumor also showed significant cytologic atypia and pleomorphism. Immunohistochemical stains showed strong staining of the histiocytoid cells and focal anastomosing-like vascular spaces for CD31 and ERG-1, but were essentially negative for CD68, lysozyme, CD163, S100, and CD1a, consistent with a vascular endothelial tumor. This case expands the spectrum of findings that can be identified in angiosarcomas, and should help to prevent potential misdiagnosis as a less aggressive tumor such as RDD.

Radiological features of Rosai-Dorfman disease: case series and review of the literature.

AIM: To improve the accuracy of diagnosis of Rosai-Dorfman disease (RDD) by summarising the computed tomography (CT) and magnetic resonance imaging (MRI) characteristics. MATERIALS AND METHODS: The clinical manifestations, imaging findings, and pathological characteristics of 14 patients with histopathologically confirmed RDD were analysed retrospectively and a literature review was undertaken. RESULTS: Of the 14 patients, nine had multiple lesions and five had single lesions. Eight patients had extranodal lesions, while six had mixed-type lesions. In patients with head and neck lesions, plain CT/MRI revealed irregularly shaped, well-defined, homogeneous, and mainly progressive lesions, with marked homogeneous enhancement on multiphasic contrast-enhanced imaging. One patient had dural lesions, one of which iso-intense to grey matter, with patchy hypo-intensity on T2-weighted imaging, meningeal tail signs, and characteristic crabfoot-like enhancement. Three patients with skeletal system involvement exhibited osteolytic bone destruction without sclerosis at the edges, associated soft-tissue masses, or periosteal reactions. Two patients had well-defined subcutaneous lesions, inhomogeneous density, and progressive parenchymal enhancement on contrast-enhanced CT. One patient had multiple intestinal lesions with inhomogeneous nodular thickening of the blind ascending colon and ileum, with marked and progressive enhancement. CONCLUSION: RDD involvement is mainly multifocal, primarily in the head and neck regions. Plain CT/MRI revealed well-defined, irregularly shaped lesions with homogeneous density/signal, with marked and progressive enhancement on multiphasic contrast-enhanced imaging; however, histopathology is still required to confirm the diagnosis of RDD.

Cutaneous Rosai-Dorfman disease in a 3-year-old boy.

The cutaneous form of Rosai-Dorfman disease is very rare in childhood. The clinical spectrum is highly variable and histopathological study with immunohistochemistry is essential for the diagnosis. We present the case of a 3-year-old boy with the diagnosis of cutaneous Rosai-Dorfman disease and review the pediatric cases published in the literature.

Primary cutaneous Rosai-Dorfman-Destombes disease with features mimicking IgG4-related disease: A challenging case report and literature review.

Rosai-Dorfman-Destombes disease (RDD) is a rare histiocytic disorder affecting lymph nodes as well as extranodal sites. Although cutaneous involvement in RDD is common, primary cutaneous RDD is a distinct and not well-documented entity with unknown aetiology and non-specific clinicopathological features. We report a case of a 57-year-old patient, who presented with an indolent skin nodule in the left sub-nipple area. Surgical excision was performed. Histological examination concluded to the diagnosis of cutaneous RDD with histological features mimicking IgG4-related disease. The diagnosis of systemic RDD with cutaneous involvement was ruled out after exclusion of extracutaneous involvement. No recurrence or systemic progression was observed during follow-up. The diagnosis of primary cutaneous RDD is very uncommon and hence is challenging for pathologist and dermatologist especially with features of IgG4-related disease. Careful systemic and microscopic examinations help in establishing the appropriate diagnosis.