Primary mediastinal seminoma with florid follicular lymphoid hyperplasia: a case report and review of the literature

Abstract

Background First described in 1955 Primary mediastinal seminomas are rare. Only 1–4% of mediastinal tumours are germ cell tumors; majority of which are teratomas. They typically present in men aged between 20 and 40 years. Very few cases are reported in the literature. Florid follicular lymphoid hyperplasia can obscure the malignant cells and is a rarer finding still. We present a rare case of a 48 year old man with a primary mediastinal seminoma with florid follicular lymphoid hyperplasia; found following excision of a clinically presumed thymoma. Case presentation A 48 year old man was referred for excision of a thymic mass. The presumed diagnosis was a thymoma; following preoperative investigations. The mass was incidentally found on a radiological imaging. However, the patient did report mid-sternal discomfort on lying flat and breathlessness. The patient underwent a thymectomy via a partial median sternotomy with good recovery. Histological assessment was that the mass was in fact a primary mediastinal seminoma with florid follicular lymphoid hyperplasia. A primary testicular malignancy was excluded and the patient required no further oncological treatment. Conclusions Only 11 cases have previously been reported of primary mediastinal seminoma with florid follicular lymphoid hyperplasia. Although rare, a primary mediastinal seminoma should be considered as a differential diagnosis for presentations with a thymic mass. Tumour markers can be helpful, however are only positive in third of cases. Ultrasound imaging of the gonads is essential to exclude a primary gonadal lesion. Pure seminomas are radiotherapy and chemotherapy sensitive however the mainstay treatment of primary mediastinal seminomas remains surgical excision. Radiotherapy is reserved postoperatively for incomplete surgical margins.

Primary mediastinal seminoma with chronic granulomatous inflammation and lymphoid follicular hyperplasia: A case report and literature review

“…Previous studies have reported misdiagnosis of PMS with thymic cyst and/or lymphoid hyperplasia and/or granulomatous in ammation [10][11][12]. These accompanying features often hide tumors and lead to missed diagnosis or misdiagnosis and delayed diagnosis.…”

Primary germ cell tumours of the mediastinum: A review with emphasis on diagnostic challenges

“…They show a sheet‐like and solid or lobular growth pattern, usually forming nests of tumour cells separated by thin fibrous septa (Figure 1A–B). There can be prominent lymphocytic infiltrates with florid lymphoid hyperplasia 81,82 or granulomatous reactions (Figure 1A) mimicking granulomatous diseases and effacing tumour cells 83,84 . Contrary to their gonadal counterpart, up to 8% of PMSEMs show cystic changes due to the induction of tumour‐associated multilocular (secondary) thymic epithelial cysts 85 .…”

Primary mediastinal seminoma presenting with paraneoplastic anti-Hu encephalitis: a case report and literature review

“…Despite presenting as a diagnostic challenge, PMS can present with distinct complications often related to mass effect. Known common complications of mediastinal tumors include superior vena cava (SVC) syndrome ( 8 ), chylothorax ( 9 ), pericardial effusion ( 10 ), and lymphoid hyperplasia ( 5 , 11 ). When planning for surgical removal, these tumors require remarkable precision, skill, and planning due to the nature of their location and adjacency to surrounding tissues.…”

“…This is likely due to the rarity of the tumor, but also because this tumor type can be difficult to diagnose. Prior to full histologic evaluation, these tumors are often mistaken for thymic or thyroid neoplasms (3)(4)(5). For example, seminoma tumor cells have a CD117+ immunohistochemical (IHC) phenotype, a pattern also seen in thymic tumors (6).…”