OBJECTIVE: We evaluated the magnetic resonance imaging (MRI) features of ovarian teratomas with somatic-type malignancy (TSMs) and benign ovarian mature cystic teratomas (MCTs) to determine the diagnostic contribution of the MRI findings for differentiating these two teratomas.
METHODS: We compared the MRI findings between ovarian TSMs (n = 10) and MCTs (n = 193), and we conducted a receiver operating characteristic (ROC) analysis to determine the MRI findings\' contribution to the differentiation of TSMs from MCTs.
RESULTS: The maximum diameters of whole lesion and the largest solid component in the TSMs were larger than those of the MCTs (p = 0.0001 and p < 0.0001, respectively). Fat tissue in solid components was seen in 73/116 (62.9%) MCTs but in none of the TSMs (p = 0.0001). Ring-like enhancement in solid components was seen in 60/116 (51.7%) MCTs and none of the TSMs (p = 0.0031). On dynamic contrast-enhanced MRI (DCE MRI), all of the solid components in the TSMs showed a high- or intermediate-risk time intensity curve (TIC), and those in 113 of the 116 (97.4%) MCTs showed a low-risk TIC (p < 0.0001). The area under the curve of the ROC analysis using the high-/intermediate-risk TIC on DCE MRI was the highest (0.99) for differentiating TSMs from MCTs: sensitivity 100%, specificity 97.4%, positive predictive value 75.0%, negative predictive value 100%, and accuracy, 97.6%.
CONCLUSIONS: Compared to ovarian MCTs, ovarian TSMs are larger and have larger solid components with high- or intermediate-risk TICs on DCE MRI. Ovarian MCTs frequently show small solid components with fat tissue, ring-like enhancement, and a low-risk TIC on DCE MRI.

Somatic-type malignancy (STM) can occur infrequently within a primary or metastatic testicular germ cell tumor (TGCT) and is associated with dismal prognosis and survival. STM with chondrosarcomatous features is exceedingly rare and head and neck involvement has not been previously documented. A 39-year-old white man presented with nasal obstruction and epistaxis. Imaging disclosed a 6.9-cm expansile tumor involving the nasal cavity and skull base with intraorbital and intracranial extension. The histopathologic properties of the tumor were compatible with chondrosarcoma, grade II-III. Immunohistochemically, malignant cells were strongly and diffusely positive for S100 and epithelial markers, and showed loss of SMARCB1 expression. IDH1/2 mutations were not detected. Following whole-body PET scan, a 7.0-cm left testicular mass was discovered and diagnosed as seminoma with syncytiotrophoblastic cells, stage pT3NXM1b. Extensive retroperitoneal, mediastinal, and supraclavicular lymphadenopathy was also noticed. Histopathologic examination of the left supraclavicular lymph node revealed metastatic seminoma. By FISH, most metastatic nodal seminoma cells harbored 1 to 4 copies of isochromosome 12p, while the chondrosarcoma featured duplication of 12p. Presence of a malignant TGCT with disseminated supradiaphragmatic lymphadenopathy, the unique immunophenotypic properties of the skull-based chondrosarcoma and lack of IDH1/2 aberrations with gain of 12p strongly support the diagnosis of STM chondrosarcoma arising from metastatic TGCT. The patient did not respond to chemotherapy and succumbed three months after diagnosis. Although exceedingly uncommon, metastasis to the head and neck may occur in patients with TGCT. This case of STM chondrosarcoma demonstrated divergent immunophenotypic and molecular characteristics compared to \"typical\" examples of head and neck chondrosarcoma. High index of suspicion is advised regarding the diagnosis of lesions that present with otherwise typical histomorphology but unexpected immunohistochemical or molecular features.

In the post-chemotherapy setting, germ cell tumors of the testis (GCTT) that resemble non-specific sarcomas and co-express cytokeratins and glypican-3 (GPC3) are diagnosed as \"sarcomatoid yolk sac tumor postpubertal-type (YSTpt)\". The diagnosis of sarcomatoid YSTpt is clinically relevant but challenging due to its rarity, non-specific histology, and negative α-fetoprotein (AFP) staining. Recently, FOXA2 has emerged as a key-gene in the reprogramming of GCTT (activating the transcription of several genes, among which GATA3), and immunohistochemical studies showed that GATA3 and FOXA2 have a higher sensitivity for non-sarcomatoid YSTpt than GPC3 and AFP. We found that sarcomatoid YSTpt did not express FOXA2 [0: 14/14 (100%)] and showed focal expression of GATA3 [0: 12/14 (85.7%), 1 + : 2/14 (14.3%)], thus suggesting that these markers are not useful in diagnosing this tumor. Furthermore, we proposed a potential mechanism of sarcomatoid transformation in the post-chemotherapy setting of GCTT, mediated by the downregulation of FOXA2 and GATA3.

This article will review current aspects of the histopathological, immunohistochemical and molecular analysis of primary mediastinal germ cell tumours (PMGCTs) as well as their aetiological, epidemiological, clinical and therapeutic features. PMGCTs represent an important differential diagnosis in the spectrum of mediastinal tumours, and their diagnosis is usually made on small tissue samples from core needle biopsies in combination with diagnostic imaging and serum tumour markers. As in lymphomas, a small biopsy is often the only viable tumour sample available from these patients, as they receive chemotherapy prior to eventual surgical resection. Pathologists therefore need to apply an efficient combination of immunohistochemical markers to confirm the diagnosis of a PMGCT and to exclude morphological mimics.

The development of somatic-type malignancy (SM) in testicular germ cell tumor represents a major challenge in the diagnosis and treatment of testicular cancer. Most SMs are derived from teratoma, and the remainder is associated with yolk sac tumor. They occur more frequently in metastases than in primary testicular tumors. SMs demonstrate a variety of histologic types, including sarcoma, carcinoma, embryonic-type neuroectodermal tumor, nephroblastoma-like tumor, and hematologic malignancy. Sarcoma, particularly rhabdomyosarcoma, accounts for the majority of SMs in the primary testicular tumors, whereas carcinoma, particularly adenocarcinoma, is the most common SM in metastases. Although SMs derived from testicular germ cell tumors mimic their histologic counterparts in other organs with overlapping immunohistochemical profiles, isochromosome 12p is present in most SMs, which can be useful in the differential diagnosis. The presence of SM in the primary testicular tumor may not worsen the outcome, but the development of SM in metastasis is associated with a poor prognosis. Furthermore, somatic-type carcinoma is likely associated with a worse prognosis than somatic-type sarcoma. Although SMs respond poorly to the cisplatin-based chemotherapy, timely surgical resection is an effective treatment for most patients.

The development of somatic-type malignancy (SM) in testicular germ cell tumor represents a major challenge in the diagnosis and treatment of testicular cancer. Most SMs are derived from teratoma, and the remainder is associated with yolk sac tumor. They occur more frequently in metastases than in primary testicular tumors. SMs demonstrate a variety of histologic types, including sarcoma, carcinoma, embryonic-type neuroectodermal tumor, nephroblastoma-like tumor, and hematologic malignancy. Sarcoma, particularly rhabdomyosarcoma, accounts for the majority of SMs in the primary testicular tumors, whereas carcinoma, particularly adenocarcinoma, is the most common SM in metastases. Although SMs derived from testicular germ cell tumors mimic their histologic counterparts in other organs with overlapping immunohistochemical profiles, isochromosome 12p is present in most SMs, which can be useful in the differential diagnosis. The presence of SM in the primary testicular tumor may not worsen the outcome, but the development of SM in metastasis is associated with a poor prognosis. Furthermore, somatic-type carcinoma is likely associated with a worse prognosis than somatic-type sarcoma. Although SMs respond poorly to the cisplatin-based chemotherapy, timely surgical resection is an effective treatment for most patients.

OBJECTIVE: Malignant germ cell tumours (GCTs) of the testis are rare neoplasms, but the most common solid malignancies in young men. World Health Organization guidelines divide GCTs into five types, for which numerous immunohistochemical markers allow exact histological subtyping in the majority of cases. In contrast, a germ cell origin is often hard to prove in metastatic GCTs that have developed so-called somatic malignant transformation. A high percentage, up to 89%, of GCTs are characterised by the appearance of isochromosome 12p [i(12p)]. Fluorescence in-situ hybridisation has been the most common diagnostic method for the detection of i(12p) so far, but has the disadvantages of being time-consuming, demanding, and not being a stand-alone method. The aim of the present study was to establish a quantitative real-time polymerase chain reaction assay as an independent method for detecting i(12p) and regional amplifications of the short arm of chromosome 12 by using DNA extracted from formalin-fixed paraffin-embedded tissue.
RESULTS: A cut-off value to distinguish between the presence and absence of i(12p) was established in a control set consisting of 36 tumour-free samples. In a training set of 149 GCT samples, i(12p) was detectable in 133 tumours (89%), but not in 16 tumours (11%). In a test set containing 27 primary and metastatic GCTs, all 16 tumours with metastatic spread and/or somatic malignant transformation were successfully identified by the detection of i(12p).
CONCLUSIONS: In summary, the qPCR assay presented here can help to identify, further characterise and assign a large proportion of histologically inconclusive malignancies to a GCT origin.

A 54-year-old male presented with exertional dyspnea, right massive pleural effusion, and an anterior mediastinal tumor (6.5 × 6.2 × 7.6 cm) which continued to grow during the 11-year follow-up period. Fluorodeoxyglucose positron emission tomography demonstrated a focal but remarkable uptake within the tumor mass. After chest tube drainage, the patient underwent surgical resection via a right thoracotomy. The final pathology was determined to be a mature cystic teratoma with malignant transformation to adenocarcinoma. Teratomas with somatic-type malignancy are challenging to diagnose using only preoperative evaluations. Intra-operative findings, histopathological findings, and postoperative management techniques are discussed in this report and emphasize the importance of early resection for treatment of mature teratomas, as well as the recommendation of careful inspection of pathological specimens of long-standing teratomas.