Thymic inflammatory pseudotumor with multilocular thymic cyst caused by immunoglobulin G4‐related disease

Abstract

A 44‐year‐old man was referred to our hospital after an anterior mediastinal tumor was noted on computed tomography during follow‐up observation after left testicular seminoma resection. Chest computed tomography revealed an enhanced mass measuring 33 x 16 x 15 mm at the anterior mediastinum. Chest magnetic resonance imaging revealed high signal intensity on T2‐weighted imaging, and F18 fluorodeoxyglucose‐positron emission tomography showed a maximum standardized uptake of 12.45. Laboratory tests revealed no elevated tumor markers, except for mildly elevated interleukin‐2. Based on these results, complete resection was performed under suspicion of a malignant tumor, mediastinal metastasis of seminoma, or malignant lymphoma. An extended thymectomy with partial merger pericardial resection was performed using a subxiphoid approach. Small nodules and multiple thymic cysts were observed the thymus in addition to the main mass. Microscopic examination of the tumor revealed fibrosis, lymphocyte infiltration with lymphoid follicular hyperplasia, and hyperplasia of the thymus. Numerous immunoglobulin G4 (IgG4)‐positive plasma cells were found on immunohistochemical staining. The ratio of IgG4 to total IgG was approximately 60%. We ultimately diagnosed the patient with a thymic inflammatory pseudotumor with multilocular cyst caused by IgG4‐related disease.

Mediastinal tumours and pseudo-tumours: a comprehensive review with emphasis on multidisciplinary approach

“…They are idiopathic or secondary to autoimmune diseases such as Sjögren syndrome [66] or HIV infection [67]. One case has been reported in association with IgG4-related disease [68]. Importantly, multilocular cysts may result from local inflammation related to neoplasms and especially lymphomas, seminoma or thymic epithelial tumours [69].…”

Marginal zone B-cell lymphoma: lessons from Western and Eastern diagnostic approaches

“…The differential diagnoses include multilocular thymic cyst, lymphoepithelial sialadenitis-like thymic hyperplasia, thymic follicular hyperplasia, and thymic IgG4-related disease. [76][77][78] Thymic MALT lymphomas have a high frequency of trisomy 3, a low incidence of trisomy 18, and an absence of translocations involving MALT1 or IGH. 79,80 Deletion of TNFAIP3 (encoding A20, an NF-kB inhibitor) has been reported in one case.…”

IgG4-related Diaphragmatic Inflammatory Pseudotumor

“…We reviewed 19 IgG4-related IPTs that occurred at uncommon sites (fewer than 3 cases reported) (Table ) [please check this carefully] (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36). The lesions were located at the breast in three cases, epidural in two cases, mediastinum in two cases, paratestis in two cases, urethra in two cases, and oral cavity, trachea, adrenal gland, bladder, rectum, abdominal wall, pericardium, uterine in one case each.…”