Immature mediastinal teratoma with unusual histopathology: A case report of multi-lineage, somatic-type malignant transformation and a review of the literature

Abstract

Germ cell tumors (GCTs) represent a well-recognized group of heterogeneous neoplasms with diverse clinical, histopathological, diagnostic, and prognostic characteristics. We present a rare case of a locally aggressive, chemotherapy-resistant immature mediastinal teratoma with a peculiar histological finding of a multilineage somatic-type malignant degeneration. A 21-year-old male patient presented with a 3-week history of persistent, blood-tinged productive cough and shortness of breath. A contrast-enhanced computed tomography (CT) scan of the chest showed a heterogeneous mass occupying the right hemithorax and abutting on adjacent structures. CT-guided biopsy was consistent with immature teratoma. Combination chemotherapy with bleomycin, etoposide, and cisplatin was initiated, albeit without success; the mass showed interval progression in size, and surgical resection through clamshell incision was performed. Histological assessment of the resected mass confirmed the diagnosis of immature teratoma and revealed an extensive multilineage malignant differentiation into sarcomatous, carcinomatous, and melanomatous components. The patient underwent an uneventful recovery but presented 2 months later with extensive liver and bone melanomatous metastases. In this report, relevant findings from the literature are also highlighted. Despite being exceptionally rare, such tumors carry poor prognosis. Understanding the clinicopathological characteristics and biological behavior of such tumors may provide an insight into interventions tailored to improve the otherwise dismal disease outlook.

Figure 1

(A, B) A contrast-enhanced computed tomography scan, using the mediastinal (A) and lung (B) windows, showing a mediastinal mass that is extending into the adjacent lung.

Figure 2

(A, B) Microscopic examination of needle core biopsy from the mediastinal mass showing predominant immature neuroectodermal elements forming glands and tubules lined by columnar embryonal cells with stratified hyperchromatic nuclei (A) and focal areas of a more mature neural tissue (B).

Figure 3

A whole-body combined 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography scan showing an FDG-avid mediastinal mass with an intense peripheral hypermetabolic activity.

Figure 4

(A, B) Axial (A) and coronal (B) contrast-enhanced computed tomography scans—obtained after receiving 2 chemotherapeutic cycles—showing interval progression of size, reaching around 12 × 13 × 12 cm³ in its maximum dimensions.

Figure 5

(A–C) Neural tissue with pleomorphic atypical cells and high nuclear-to-cytoplasmic ratio consistent with glioblastoma (A, B). Immunohistochemical staining of the tissue with glial fibrillary acidic protein (GFAP) showing positive reaction (C).

Figure 6

(A–H) Somatic-type malignancies: pleomorphic spindle to round cells and frequent atypical mitosis suggestive of sarcomatous differentiation (A). Malignant spindle cells with melanin pigment (B–D) which were positive for Melan-A (E). Malignant glandular epithelium depicting adenocarcinoma component (F). Cartilage with numerous lacunae containing small chondrocytes, surrounded by immature mesenchymal cells (G). Metastatic squamous cell carcinoma in a regional lymph node (H).