Testicular germ cell tumors (GCT) arise from embryonic or extraembryonic differentiated totipotential germ cells. The tumor cells can differentiate into germ cells as well as, other lineages including yolk sac tumors, choriocarcinomas, and teratomas. Mixed GCT is composed of more than one GCT component including one or more nonseminomatous elements in a tumor, accounting for one-third of GCT. Herein we report the case of a collision tumor with two distinct and separated GCTs in the testis, adjacent to each other. A 48-year-old, previously healthy man showed the hard swelling and heterogeneous enhancing mass in the right scrotum, and right orchiectomy was performed. Grossly, the lesion was two distinct and well-circumscribed masses in the testis. Microscopically, a larger tumor was immature teratoma (prepubertal type) and another smaller tumor was seminoma. These two tumors can be from a common precursor, germ cell neoplasia in situ (GCNIS); however, they are two distinct pathological entities. Given that teratomas can evolve from seminomas by additional genetic alterations, seminomas are also a precursor for postpubertal-type teratomas. Two distinct GCNISs may occur at different times. Because GCNIS is patchy distributed, a close gross examination must be performed in GCNIS or GCT to miss other GCTs with poor prognosis and to prevent under-treatment.

As a result of development in medical diagnostic technology, the incidence of double primary cancer is increasing. In case that one primary cancer was identified by pathologic finding and has suggestive multiple metastatic lesions of the cancer, it is often difficult that the lesions are considered as another synchronous primary malignancy, not as metastasis of primary cancer. Here, we report a rare case of synchronous double primary renal cell carcinoma that was diagnosed initially as metastatic duodenal adenocarcinoma. A 66-year-old man presented with a palpable abdominal mass. Abdominal computed tomography showed duodenal wall thickening and hypervascular masses in the liver and left kidney. Esophagogastroduodenoscopy revealed an ulcerative lesion in the duodenal bulb, and endoscopic biopsy identified moderately-differentiated adenocarcinoma. We regarded the findings as duodenal adenocarcinoma with metastasis to liver and kidney. So he was treated with fluoropyrimidine-based chemotherapy for the diagnosis of duodenal adenocarcinoma with liver and renal metastases. After 10 months, he developed a right forearm mass. Morphological and immunohistochemical analysis of an incisional biopsy of the forearm mass were consistent with a diagnosis of metastatic renal cell carcinoma. Even when there is a pathologically confirmed malignancy, clinicians must consider the possibility of synchronous double primary malignancy in metastatic lesions.

Malignant peripheral nerve sheath tumors (MPNSTs) are defined as malignant tumors arising from peripheral nerves or differentiating along the line of the elements of the nerve sheath. MPNSTs that originate from the brain parenchyma are exceptionally rare and are termed malignant intracerebral nerve sheath tumors. We experienced a case of the epithelioid variant of malignant intracerebral nerve sheath tumor (MINST) occurring in the right frontal lobe of a 50-year-old man. He underwent gross total resection of the tumor. Histologically, the tumor cells had round, polygonal, or ovoid nuclei and moderate amounts of eosinophilic cytoplasm, which was defined as epithelioid cells. The tumor cells were arranged in short cords or nests with vaguely nodular patterns embedded in the myxoid stroma. Regarding mitotic activity, 15 mitotic figures were noted per 10 high-power fields. Immunohistochemically, tumor cells were positive for S-100 protein and synaptophysin, but negative for glial fibrillary acidic protein, HMB-45, EMA, and AE1/ AE3. Furthermore, immunostaining for INI1 was negative. Loss of the tumor-suppressor gene product SMARCB1/ INI1 expression has been recognized in epithelioid MPNST, but not in conventional MPNST. Postoperatively, he underwent radiotherapy and was followed for almost 1 year without recurrence. The present case is the first report of the epithelioid MINST.

Localized tenosynovial giant cell tumor (TGCT) usually occurs in the hand and foot regions. However, localized TGCT with extensive cartilaginous metaplasia is rare, especially in the tendon sheath of the toe. Here, we report a case of localized TGCT with cartilaginous metaplasia in a 57-year-old man. The tumor presented as a lobular mass measuring 2.2 cm in its greatest dimension and arose in the flexor digitorum tendon sheath of the right 2nd toe. Clinically, the mass was palpable 1 year ago and brought pain during walking. Microscopically, the mass was composed of focal conventional TGCT and cartilaginous components. The conventional TGCT areas consisted of mononuclear cells, multinucleated giant cells, and hemosiderin deposition. The chondroid areas were extensive and comprised more than 90% of the whole tumor. In this case, the mononuclear cells in the conventional TGCT areas showed focal immunohistochemical staining for podoplanin and S100 protein as well as diffuse staining for CD68, which is consistent with the staining pattern of conventional TGCT. The mononuclear cells in the chondroid areas were focal positive for podoplanin and diffuse positive for S100 protein. Chondroid metaplasia in diffuse TGCT has been reported in 10 cases involving the temporomandibular, elbow, and hip joints. However, there has been no report of a localized form of chondroid TGCT involving an extra-articular region.

Malignant transformation of mature cystic teratoma (MCT) is rare. Sarcomatoid carcinoma is a neoplasm comprising malignant mesenchymal cells and a conventional carcinomatous area. Here, we report on a case of sarcomatoid carcinoma arising from an MCT in the left ovary of a 45-year-old female. A unilocular cyst consistent with MCT was observed; however, a nodule within the cyst was confirmed from the resected ovary. Microscopically, the nodule showed both squamous cell carcinoma and pleomorphic sarcomatous components admixing with each other. Lining epithelial cells at the periphery of the main tumor showed squamous metaplasia. When a sarcomatous component is observed in the ovary tumor, it is important to find a squamous cell component, either benign or malignant.

Malignant pleural effusion (MPE) and blood samples can be used as a practical source for detection of epidermal growth factor receptor (EGFR) mutations in patients with advanced non-small cell lung cancer. We compared EGFR mutation status of cell blocks, cell-free fluid of MPE, and plasma from patients with lung adenocarcinoma. We obtained paired samples of MPE and plasma from 14 pathologically-confirmed lung adenocarcinoma patients. Peptide nucleic acid (PNA)-mediated real-time polymerase chain reaction (RT-PCR) clamping was performed for determination of EGFR mutation status. EGFR mutations were detected in five (35.7%) cell blocks of MPE, which showed results identical to those of the corresponding cell-free fluid, whereas mutations were detected in the plasma of only two (40.0%) of the five patients. Of seven patients treated with EGFR tyrosine kinase inhibitors (TKIs), EGFR mutations were detected in cell blocks, cell-free fluid of MPE, and plasma for only one of the four patients who responded to EGFR TKIs, while mutations were detected only in cell blocks of MPE and cell-free fluid of the three remaining patients. Our results suggest that detection of EGFR mutations in cell-free pleural fluid from lung adenocarcinoma patients using highly sensitive methods may be feasible, but that analysis of free plasma may lead to undetected mutations and misdiagnosis.