Treatment and outcomes in pediatric inflammatory myofibroblastic tumors - A systematic review of published studies.

Inflammatory myofibroblastic tumor (IMT) is a soft tissue neoplasm which can be locally invasive, recur, or in rare cases metastasize. Often originating from the abdomen or thorax, IMT most commonly affects children and young adults. Due to its rarity comprehensive reports detailing clinical management and outcome(s) are sparse and often based on limited index case numbers. This study systematically analyzes outcome metrics of pediatric IMT and identifies risk factors for mortality. Medline/Embase databases were searched in accordance with PRISMA guidelines. Final analysis included 57 studies with 673 IMT patients (355 males, 53 %). Individual patient data was available for 405 cases with a median follow-up period of 36 months. Tumor sites included abdomen/pelvis (n = 233, 58 %), thorax (n = 125, 31 %), head/neck (n = 34, 8 %), and extremities (n = 13, 3 %). Surgical tumor resection was the mainstay of treatment, while only 20 patients (5 %) were treated non-operatively. Recurrence(s) were reported in 80 patients (20 %) with 34 (12 %) requiring reoperation. Positive tumor margins were a significant risk factor for tumor recurrence (p < 0.0001). Chemo/radiotherapy was reported in 98 patients (25 %). Most patients (94 %) survived; 81 % (n = 237) with no evidence of recurrent disease, 14 % (n = 41) were alive with disease, and 25 (6 %) died of disease. Positive margins at primary operation, and metastatic disease were associated with mortality (p < 0.0001 for both). IMT is a rare tumor with favorable outcome for the majority of patients. Whilst most patients will present with benign tumors, complete surgical resection (R0) is crucial, as positive surgical margins are a significant risk factor for tumor recurrence and mortality.

Photodynamic therapy for cutaneous inflammatory pseudotumour: A case report.

Inflammatory pseudotumour (IP) is a rare proliferative disease characterized by a dense infiltrate of plasma cells, lymphocytes, eosinophils and neutrophils in the fibrous stroma. It primarily affects the lungs of pediatric patients or young adults. Cutaneous IP is an extremely rare condition, with limited documentation in the English literature. In this case report, we presented an unusual instance of a 62-year-old male endured recalcitrant cutaneous IP for 8 years and exhibited poor response to topical glucocorticoid therapy, as well as intralesional injections of pingyangmycin and/or corticosteroid. Notably, after undergoing four sessions of 5-aminolevulinic acid photodynamic therapy (ALA-PDT), the patient experienced a significant reduction in erythema and nodules. This observation suggests that ALA-PDT may represent a promising and safe treatment option for cutaneous IP.

Management Strategies of Plasma Cell Granuloma Involving the Central Nervous System: A Systematic Review of the Literature.

BACKGROUND: Plasma cell granuloma (PCG) is a rare clinical entity seen in the neurosurgical literature. It has often been referred to as inflammatory myofibroblastic tumor or inflammatory pseudotumor. No well-defined management guidelines exist in the literature. METHODS: Using PRISMA guidelines, we systematically reviewed the literature in PubMed and Google Scholar using MeSH terms: intracranial plasma cell granuloma, myofibroblastic tumor, intracranial pseudotumor, spinal plasma cell granuloma. We analyzed the clinical presentation, treatment strategies, clinical outcomes, and follow-up across different studies. RESULTS: Eighty-three studies were included presenting 108 cases. Primary extracranial disease was seen in 4 patients and primary central nervous system (CNS) disease in 104. In the combined cohort, multicompartmental disease was seen in 22 (20.8%) patients. Headache (n=40, 42.59%) was the most common clinical symptom. Surgical excision (n=86, 79.6%) was the most common primary treatment used. Radiation therapy, steroids, and chemotherapy (methotrexate/6-mercaptopurine/rituximab) were also used. Disease recurrence was noted in 25 (33.3%) patients and residual disease in 33 (30.5%). Mortality was seen in 4 (3.7%) patients. In the cranial PCG subgroup (n=87), 81 (93.1%) patients had solitary lesions, and 6 (6.8%) had multiple lesions. Recurrence after primary surgery was noted in 27.58% (n=24). In the spinal PCG subgroup (n=17), the thoracic spine was the most common location (n=9, 52.9%) and recurrence was seen in 5.84% (n=1). CONCLUSIONS: Combination of multiple treatment modalities is needed when approaching this complex disease. Spinal PCGs respond favorably to gross total excision, with a low recurrence rate. Cranial PCGs warrant intense follow-up with secondary chemotherapy/radiation/steroids in recurrent cases.

Un caso singular de granuloma de cèlulas plasmáticas y actinomicosis en encía / A singular case of plasma cell granuloma and actinomycosis in the gum

Antecedentes: El granuloma de cèlulas plasmáticas (GCP) es una patología poco común que se caracteriza por una lesión roja e hiperplasia que presenta una gran afinidad a cualquier tejido blando con mayor frecuencia a nivel pulmonar y de manera poco usual a nivel oral como los labios, lengua y encía como un caso muy singular, histológicamente se caracteriza por un gran número de cèlulas plasmáticas. Objetivo: Reportar un caso poco común de GCP en encía con el abordaje, complicaciones y èxito del tratamiento del mismo. Descripción del caso: paciente femenino de 60 años de edad, acude a consulta por una lesión roja nivel de la encía marginal y adherida del maxilar superior. Al examen intraoral se observa una hiperplasia localizada Con diagnostico presuntivo de granuloma de cèlulas plasmáticas, donde se le realizaron exámenes radiográficos, posteriormente una biopsia, confirmando dicho diagnóstico. Conclusión: GCP se caracteriza clínicamente por presentar una hipertrofia gingival en la encía adherida, una de los lugares menos frecuentes a nivel oral. Esta patología al presentar ciertas similitudes clínica e histológicamente es muy difícil realizar un correcto diagnóstico de dicha patología (AU)

Background: Plasma cell granuloma (PCG) is an uncommon pathology characterized by a red lesion and hyperplasia that has a high affinity to any soft tissue, more frequently at the lung level and in an unusual way at the oral level such as lips, tongue and gingiva as a very unique case, histologically characterized by a large number of plasma cells. Objective: To report a rare case of GCP in the gingiva with the approach, complications and success of its treatment. Description of the case: a 60-year-old female patient comes to the clinic for a red lesion at the level of the marginal and attached gingiva of the upper jaw. Intraoral examination revealed localized hyperplasia with a presumptive diagnosis of plasma cell granuloma, where radiographic examinations were performed, followed by a biopsy, confirming said diagnosis. Conclusion: GCP is clinically characterized by presenting gingival hypertrophy in the attached gingiva, one of the least frequent places at the oral level. This pathology, as it presents certain clinical and histological similarities, is very difficult to make a correct diagnosis of said pathology. (AU)

Role of myofibroblasts in oral plasma cell granuloma: Immunohistochemical evaluation of α-SMA and ALK in a retrospective study of 30 cases.

INTRODUCTION: Oral plasma cell granuloma (OPCG) is a rare reactive lesion with generally benign yet occasionally aggressive behavior. Myofibroblasts are important in many physiologic, and pathologic conditions. The role of myofibroblasts in the clinical behavior of OPCG was assessed as well as its usefulness in differentiating this lesion from the inflammatory myofibroblastic tumor mimicking plasma cell granuloma. MATERIAL AND METHODS: This retrospective study included 30 paraffin blocks of OPCG. Immunohistochemical evaluation of alpha-smooth muscle actin (α-SMA) and Anaplastic lymphoma kinase (ALK) antibodies was performed. The mean area of positive expression was calculated and scored semiquantitatively with clinicopathologic correlations. RESULTS: Most of the cases were clinically non-aggressive. Alveolar bone resorption was observed in nine cases, two of them showed severe resorption and stromal fibrosis. Negative α-SMA was observed in 70% of cases showing a predominance of plasma cells in the stroma. All cases of stromal fibrosis revealed positive α-SMA of a weak percentage. A statistically significant difference was observed between α-SMA expression and the clinicopathologic variables. Negative ALK expression was noted in all cases. DISCUSSION: Myofibroblasts were infrequently found in OPCG. Remarkably, the aggressive behavior in cases with intense fibrosis was related to the existence of myofibroblasts even of non-neoplastic nature and minimal amount. The number of myofibroblasts and their nature assessed via α-SMA and ALK immunohistochemical expression respectively might be valuable in predicting the biological behavior of OPCG and may hold diagnostic significance in challenging OPCG cases that might mimic inflammatory myofibroblastic tumor.

IgG4 inflammatory pseudotumor mimicking primary lung cancer.

Introduction: IgG4 related disease (IgG4-RTD) is an infrequent disease with possible multiple organ involvement. It is characteristic to find inflammatory nodules with IgG4 positive plasma cell infiltration, storiform fibrosis and obliterative phlebitis. We present a patient with an inflammatory pseudotumor in the right upper lobe, mimicking a primary lung tumor. Case report: Our patient, a 48-year old heavy smoker (25 pack/year) with no relevant medical background, referred chest pain, non-productive cough and sporadic nightly fever. Image findings revealed a mass in the right upper lobe, with increased SUV in PET-scan, and mediastinal lymphadenopathies. Primary lung tumor was suspected and right upper lobectomy was performed. Due to absence of cellular atypia and the intense plasmacytic activity in the lesion, immunohistochemical analysis was performed: abundant IgG4 plasma cells were identified, with a IgG4/IgG relation of 74%. Diagnosis of IgG4- inflammatory pseudotumor was made. Discussion: After an extensive bibliographic review, we found just one similar case reported with an IgG4-lung pseudotumor without systemic disease.  Due to the broad spectrum of clinical features of IgG4-RTD, and the  potential multiple organ involvement, it is hard to find a classification and diagnostic criteria with high sensitivity and specificity, nevertheless they can be useful in clinical practice. Conclusion: There are several benign inflammatory diseases which can mimic a primary lung tumor. Although incidence is low, IgG4 pseudotumor should be considered as a differential diagnosis in the absence of malignancy.

Introducción: La enfermedad relacionada con IgG4 (IgG4-RTD) es una enfermedad poco frecuente con posible afectación multiorgánica. La presencia de infiltrados linfoplasmocitarios con células plasmáticas positivas para IgG4, fibrosis y flebitis obliterante. Presentamos el caso de un paciente con un pseudotumor inflamatorio en el lóbulo superior derecho, con presentación clínica compatible con tumor primario de pulmón. Caso clínico: Nuestro paciente de 48 años de edad, tabaquista severo (25 paquetes / año) sin antecedentes médicos relevantes, consulta por dolor torácico, tos no productiva y registros subfebriles aislados. Presenta una masa en el lóbulo superior derecho en estudio por imagen, con aumento de la captación en el PET, asociado a adenopatías mediastínicas. Con diagnóstico inicial de cáncer de pulmón, se realizó lobectomía superior derecha. Debido a la ausencia de atipia celular y la presencia de infiltrados linfoplasmocitarios en la lesión, se realizó análisis inmunohistoquímico: se identificaron abundantes células plasmáticas positivas para IgG4, con una relación IgG4 / IgG del 74%. Se realizó el diagnóstico de pseudotumor inflamatorio por IgG4. Discusión: Tras una extensa revisión bibliográfica, sólo encontramos un caso similar, de una paciente con un pseudotumor pulmonar IgG4 sin enfermedad sistémica. Debido a la variabilidad de la presentación clínica de la enfermedad relacionada a IgG4, y su potencial afectación multiorgánica, es difícil encontrar una clasificación y criterios diagnósticos con alta sensibilidad y especificidad, sin embargo estos suelen ser útiles en la práctica clínica. Conclusión: Múltiples enfermedades inflamatorias son diagnóstico diferencial de tumor primario de pulmón. Si bien la incidencia es baja, el pseudotumor IgG4 debe considerarse como un diagnóstico diferencial cuando no hay evidencia de enfermedad neoplásica.

[Endobronchial presentation of an inflammatory myofibroblastic tumor]. / Présentation endobronchique d'une tumeur myofibroblastique inflammatoire.

INTRODUCTION: Inflammatory myofibroblastic tumors are a rare cause of primary lung tumors, most often solitary and in more than 50% of cases detected in individuals under 40 years of age. OBSERVATION: A 17-year-old patient consulted in pneumology for development of hemoptysis over a period of two weeks. Thoracic computed tomography revealed a left lower lobe cavity 24mm in diameter with bronchial fistulation and hydro-aeric level. Bronchial fibroscopy by mini-endoscope highlighted an endobronchial lesion in a subdivision of the sub-segmental posterior aspect of the left lower lobe. Paraclinical assessment highlighted a probable inflammatory myofibroblastic tumour. A surgical intervention was indicated and a lower left lobectomy performed. Histological analysis confirmed the presence of the tumour, which was resected in healthy margins by left lower lobectomy.

Treatment and Prognosis of Inflammatory Pseudotumor of the Skull Base.

Background Inflammatory pseudotumor (IPT) of the skull base is a rare, locally destructive lesion managed with a variety of treatments. We explore the impact of treatment on outcome and assess the prognosis of IPT. Methods This is a retrospective review of IPT of the skull base at a tertiary academic medical center. The primary outcome was radiographic progression after treatment. Outcome versus tumor location was also examined and a prognostic model was developed using a logistic regression. Results The demographics of 21 patients with IPT are reported. Treatment consisted of corticosteroids (in 80.1% of patients), disease modifying antirheumatic drugs (DMARDs; 33.3%), surgical resection (28.6%), radiation (23.8%), antibiotics (14.3%), chemotherapy (rituximab; 9.5%), and antivirals (4.8%). At 50.7 months, 50.8% had radiographic progression. Local therapy trended toward having a better response than systemic therapy ( p = 0.60). IPT of the orbit required 2.4 treatment modalities, compared with 2.0 for pharyngeal IPT, and 1.3 for posterior skull base masses ( p = 0.14). A total of 75% orbital IPT underwent radiographic progression, compared with 71% of pharyngeal IPT and 50% of posterior skull base masses ( p = 0.62). Sixteen patients were used to create the logistic model of radiographic progression. The Cox-Snell R 2 was 0.71 ( p = 0.03). No individual variables were statistically significant. Conclusion To our knowledge, this is among the largest sample of cases describing the presentation, treatment, and prognosis of IPT of the skull base. Our data suggest that there may be an improved response with local therapy over systemic therapy and better prognosis among posterolateral skull base masses.

A Rare Case of Hormone-Induced Plasma Cell Granuloma of the Gingiva.

Plasma cell granuloma (PCG), also known as inflammatory pseudotumor, is of unknown etiopathogenesis. It commonly presents in the lungs and can also occur in the liver, kidney, brain, and heart. PCG is rare in the oral cavity and even rarer in the gingiva. The clinical and radiological presentation of this disease in the oral cavity appears to be aggressive in nature and is often misdiagnosed as a malignant lesion. Histopathology helps in distinguishing PCG of gingiva from other benign and malignant lesions of the gingiva. Amlodipine and cyclosporine-induced PCG of gingiva have been reported in the literature. This report presents a rare case of generalized plasma cell granuloma of the gingiva in an adult female patient who was on hormonal therapy for infertility. Treatment consisted of complete surgical excision of the lesion and extraction of teeth with a poor prognosis. Wound healing was uneventful during the one-year follow-up period with no signs of recurrence.

Intraosseous inflammatory pseudotumor of the maxilla: A case report.

Inflammatory pseudotumors are benign lesions that are rarely reported in the head and neck. Moreover, intraosseous inflammatory pseudotumors of the maxilla are extremely rare, with less than 10 cases reported. A 52-year-old woman presented with recurrent dental infections; computed tomography scan of the osteolytic maxillary bone lesion and incisional biopsy were performed. Histopathological examination revealed that the lesion was composed of fascicles of fibroblasts and myofibroblasts, in addition to sheets of plasma cells, lymphocytes, and occasional other inflammatory cells. An infiltrative growth pattern was observed. Immunohistochemical staining confirmed an inflammatory pseudotumor. A partial maxillectomy was performed. There was no evidence of recurrence during the 4-month follow-up period. Inflammatory pseudotumors should be considered when treating destructive maxillary lesions. Immunohistochemical staining was performed to confirm polyclonal plasma cell proliferation.

"Inflammatory myofibroblastic tumor of the maxillary sinus: A case report".

Inflammatory myofibroblastic tumors (IMTs) are one of the most complex and rare neoplasms that have been discovered, with varying behavior in different cases. They mostly arise in the thoracic and abdominal cavity, the lungs, retroperitoneum, and extremities. They can also be detected in the head and neck area. IMTs have no age or gender preference which makes them tougher to anticipate. Head and neck IMTs are benign neoplasms with locally aggressive behavior and a low risk of metastatic spread. They have an unknown etiology, and they resemble malignant lesions radiologically. In this case report, we will review the case of a 40-year-old woman with an unusual IMT in the maxillary sinus that presented as a challenge in diagnosis and management.

Gingival plasma cell granuloma: a case report.

Plasma cell granuloma is extremely rare in the oral cavity. This paper reports a case of plasma cell granuloma in the oral cavity and reviews the literature. In this case, the plasma cell granuloma occurred in the gingiva, which was bright red and granular. The lesion was resected and diagnosed as gingival plasma cell granuloma by clinical pathological examination. Four months follow-up after operation surgery showed no signs of recurrence. Although gingival plasma cell granuloma is rare, it is easily confused with related diseases and should be identified and followed up closely.

Myofibroblastic tumor of the esophagus - a case report of long-term follow-up and literature review.

BACKGROUND: Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal neoplasm with intermediate malignant potential. Although most often seen in the lungs, it can occur at multiple anatomical locations, including the gastrointestinal tract. An esophageal lesion is extremely rare, however. IMTs present most commonly in children and young adults. The main therapeutic approach is surgical resection. CASE REPORT: We report on the follow-up of a case in a 13-year-old boy with IMT in the esophagus. He underwent surgical resection in 2013 and is free of disease to date. CONCLUSION: Surgical resection is the most preferred therapy. If the resection is complete, the risk of recurrence is low. Nevertheless, every patient should be carefully followed up after the resection.

Laryngeal Inflammatory Myofibroblastic Tumor With Anemia and Thrombocytosis.

Inflammatory myofibroblastic tumor (IMT) of the larynx is a rare benign lesion that commonly occurs in the soft tissues. We present the first case with systemic manifestations of laryngeal IMT that was associated with hypochromic, microcytic-type anemia and thrombocytosis.

Plasma cell granuloma of the conjunctiva in a young female.

Plasma cell granuloma is a rare non-neoplastic inflammatory condition of unknown etiology commonly involving lung and gastrointestinal tract. Conjunctival disease per se is very rare and usually associated with involvement of other organs. We report a case of conjunctival plasma cell granuloma without any systemic involvement in a 9-year-old girl who presented with bilateral reddish vascularised subconjunctival episcleral mass. An excision biopsy of the mass in the left eye followed by histopathologic examination and Immunohistochemistry confirmed the diagnosis. At 1 year follow-up, the child had no recurrence in the operated eye whereas the lesion remained the same in the other eye despite systemic treatment with immunosuppressants. This case is being reported for its rarity and to insist on the mandatory need for a thorough systemic workup to identify multiorgan involvement as well as to rule out other systemic disorders.

Case Report: Recurrence of Testicular Myofibroblastic Tumor After Surgery.

Inflammatory myofibroblastic tumour (IMT), also known as plasma cell granuloma (PCG) or inflammatory pseudotumour (IPT), is a distinctive, rarely metastasizing neoplasm composed of myofibroblastic and fibroblastic spindle cells accompanied by inflammatory infiltration of plasma cells, lymphocytes and/or eosinophils. IMT predominantly affects children and young adults, and the age at presentation ranges from 3 to 89 years. We present a very rare case of recurrent testicular IMT without ALK rearrangement. This case highlights the clinical characteristics and diagnostic factors associated with primary and recurrent foci of this rare tumour, along with key therapeutic approaches.

Gingival Plasma Cell Granuloma: A case Report of Multiple Lesions.

BACKGROUND: Plasma cell granuloma (PCG) is a rare benign pseudotumorous proliferation of unclear etiology that is mainly situated in the lungs. Gingival PCG is an even more peculiar lesion that usually occurs in middle-aged or elderly individuals and clinically manifests as a solitary entity. CASE REPORT: A 15-year-old male with no underlying medical conditions presented with multiple gingival masses in the right maxilla, which were initially thought to be epulis. The lesions were resected completely and the excisional biopsies sent for histological examination. Immunohistochemical (IHC) stain revealed dense polyclonal plasma cell infiltration with positive expression of both kappa and lambda light chains, confirming a diagnosis of gingival PCG. Subsequently, the affected gingiva healed uneventfully, with no sign of recurrence over 2 years of follow-up. CONCLUSIONS: The present report depicts an extremely unusual case of gingival PCG occurring in a juvenile with multiple lesions, which is worth attention in clinical pediatric dentistry. Excisional-biopsy and histological investigations are imperative for a confirmative diagnosis and to exclude potential aggressive conditions. Complete resection of lesions seems to be a valid treatment, while long-term clinical follow-up is still needed.

Sarcoidose como diagnóstico diferencial de mieloma múltiplo / Sarcoidosis as a differential diagnosis of multiple myeloma

A sarcoidose caracteriza-se como doença granulomatosa que acomete diferentes órgãos humanos, especialmente os pulmões, sendo sua patogênese pouco conhecida. No caso em questão, a paciente iniciou com sintomas inespecíficos, como fraqueza, perda ponderal e tosse seca esporádica, sendo internada para extensão da propedêutica. Sugeriu-se como hipótese diagnóstica inicial possível quadro de mieloma múltiplo, tendo em vista a anemia, a disfunção renal, a hipercalcemia e, sobretudo, as lesões osteolíticas apresentadas pela paciente. Todavia, o diagnóstico de sarcoidose foi selado a partir das biópsias de medula óssea e de linfonodo inguinal, que evidenciaram mielite e linfadenite granulomatosas, respectivamente. A terapêutica instituída baseou-se na administração de corticosteroides e em medidas de redução da calcemia. A paciente recebeu alta, com melhora do quadro clínico, para acompanhamento ambulatorial da doença. Conclui-se que a sarcoidose não possui tratamento curativo, mas a terapêutica imunossupressora é eficaz no controle da progressão da enfermidade, fazendo com que o paciente tenha um prognóstico favorável.

Sarcoidosis is characterized as a granulomatous disease that affects different human organs, especially the lungs, and its pathogenesis is little known. In this case, the patient started with nonspecific symptoms, such as weakness, weight loss, and sporadic dry cough, being hospitalized for extension of the propaedeutics. The initial diagnostic hypothesis suggested was a possible case of multiple myeloma, based on the anemia, renal dysfunction, hypercalcemia and, above all, the osteolytic lesions presented by the patient. However, the diagnosis of sarcoidosis was made after bone marrow and inguinal lymph node biopsies that showed granulomatous myelitis and lymphadenitis, respectively. The therapy instituted was based on the administration of corticosteroids and on measures to reduce the level of calcium. The patient was discharged, with clinical improvement, for outpatient follow-up of the disease. It is concluded that sarcoidosis has no curative treatment, but immunosuppressive therapy is effective in controlling the progression of the disease, giving the patient a favorable prognosis.

Cross-segment spinal plasma cell granuloma:a case report.

BACKGROUND: Plasma cell granuloma (PCG) is a rare non-neoplastic entity, with the precise etiology remaining unclear. Vertebra-affected spinal PCG has not been reported yet. This report presented a case with cross-segment spinal PCG in thoracolumbar region. CASE PRESENTATION: A 32-year-old male patient presented to the authors' hospital since his health check-up results showed osteolytic lesions in the thoracolumbar spine. He felt asymptomatic throughout the course. Radiological examination revealed destructive changes at T12 and L1 vertebrae. Whereas laboratory examination excluded malignant tumor. The results of routine incisional biopsy remained inconclusive, thereby necessitating complete excision of the lesions. Finally, the infiltration of plasma cells observed by pathological examination of the surgical specimen confirmed the diagnosis of PCG. CONCLUSIONS: To the authors' knowledge, this was the first case of cross-segment spinal PCG with osteolytic property. The possibility of PCG should be considered for the diagnosis and differential diagnosis of an osteolytic lesion in the spine. Since the etiology of PCG is unknown, the disorder was confirmed based on excluded diagnosis. Surgical resection is recommended both for the definite diagnosis and treatment of spinal PCG.

IgG4-Related Disease in the Frontal Convexity Concomitant with Smoldering Multiple Myeloma: A Case Report and Review of the Literature Regarding Therapeutic Implications.

BACKGROUND: We have reported an extremely rare case of a frontal convexity tumor diagnosed as IgG4-related disease (IgG4-RD) with unique neuroradiological images. CASE DESCRIPTION: A 64-year-old man with a history of monoclonal gammopathy of undetermined significance and conservative treatment had presented with a left facial spasm. Computed tomography showed a high-density round tumor with perifocal edema in the right frontal convexity. Magnetic resonance imaging demonstrated unique findings, including low signal intensity on T1- and T2-weighted, fluid-attenuated inversion recovery, and diffusion-weighted images, with slight gadolinium enhancement. The tumor was totally removed via right frontal craniotomy. It had been located in the subdural space, was not adherent to the dura, and was less vascular than meningiomas. Histological investigation demonstrated plasma cells that were strongly positive for IgG4 and contained κ and λ light chains at a ratio of 1.5:1. The serum IgG4 level was elevated. The tumor met the diagnostic criteria for IgG4-RD. The patient was followed up for 3 years during postoperative adjuvant steroid therapy. The steroid therapy was discontinued, and during the next 4 years, neither tumor recurrence nor symptoms were observed. CONCLUSION: Intracranial IgG4-RD with smoldering monoclonal gammopathy of undetermined significance is extremely rare. We reviewed the differential diagnosis of plasma cell granuloma and plasmacytoma, therapeutic implications, and clinical outcomes. Complete resection of a conspicuous and solitary IgG4-RD lesion in the frontal convexity is simple and could provide a cure with less-aggressive adjuvant therapy.