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Abstract  The author reports herein an extremely rare case of primary small cell carcinoma of the mediastinum with an emphasis on KIT and PDGFRA genes. A 66-year-old man was found to have a mediastinal tumor on a routine chest X-ray examination, and was admitted to our hospital. Imaging modalities revealed a 5 × 4 cm tumor in the middle mediastinum near the bronchial carina. No other tumors were detected in the body including the lungs. Video-assisted thoracoscopy confirmed the mediastinal tumor, and a large incisional biopsy was performed. The tumor was histologically small cell carcinoma. An immunohistochemical study revealed positive reactions for cytokeratins (AE1/3, polyclonal), synaptophysin, neuron-specific enolase, CD56, KIT, and PDGFRA, and negative reactions for chromogranin, CEA, CD45, CD20, and CD3. Ki-67 labeling showed a value of 80%. A molecular genetic analysis using PCR-direct sequencing identified no mutations of KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12 and 18) genes. The patient received radiation and chemotherapy, and the tumor was fully resolved. The patient has remained free of recurrence for 6 years after the first presentation. The present case is the first reported case of primary small cell carcinoma of the mediastinum with an examination of KIT and PDGFRA expressions and KIT and PDFGRA gene mutations. [ABSTRACT FROM AUTHOR]

Abstract  The author reports a rare case of primary large cystic extragastrointestinal stromal tumor (eGIST) of the transverse mesocolon with genetic analyses of the c-kit and platelet-derived growth factor receptor-α (PDGFRA) genes. A 78-year-old man was found to have a large cystic tumor in the abdomen, and the tumor was resected. Grossly, the tumor was located in the transverse mesocolon, and cystic. Microscopically, the tumor consisted of epithelioid cells with atypia. Mitotic figures were noted in five of 50 high power fields. Immunohistochemically, the tumor cells were positive for KIT, CD34, PDGFRA, and vimentin, but negative for cytokeratins, neuron specific enolase, desmin, S100 protein, α-smooth muscle actin, p53 protein, HMB45, CD68, CEA, factor VIII-related antigen, chromogranin, and synaptophysin. Ki67 labeling was 5%. Genetically, the tumor showed a point mutation (GAC → GTC) at codon 842 of exon 18 of the PDGFRA gene. Exon 12 of the PDGFRA gene and exons 9, 11, 13, and 17 of the c-kit gene showed no mutations. No recurrence is noted 3 years after the operation. This case shows that eGIST may occur in the transverse mesocolon. [ABSTRACT FROM AUTHOR]

Abstract  ‘Lymphomatosis cerebri’ (LC) is a term indicating a diffusely infiltrating form of primary central nervous system lymphoma (PCNSL) without evidence of a mass lesion. Not infrequently, diagnostic confusion is caused by its presentation on cranial magnetic resonance images (MRI), which is characterized by diffuse leukoencephalopathy without contrast enhancement. In this report, we describe a 53-year-old, immunocompetent man who had an insidiously progressive dementia and right weakness. On serial MRI in 4 months duration, diffuse white matter lesions without contrast enhancement gradually progressed, which was clinically consistent with his worsening condition. Biopsy specimen demonstrated nondestructive, diffusely infiltrating, large B-cell lymphoma, diagnosing LC. After the biopsy, corticosteroids were initiated, which dramatically alleviated his symptoms. Afterwards, he was treated by whole brain irradiation (total 36Gy) and discharged without noticeable deficits. Diagnosis of LC requires additional examinations generally not performed in the other white matter disorders. In suspected cases, biopsy should be performed to avoid deferring adequate cytostatic treatment. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented regarding the case of a 68-year-old Japanese woman diagnosed with sarcomatoid squamous cell carcinoma (SSCC) in the uterine cervix.