Primary small cell carcinoma of the mediastinum: a case report with immunohistochemical and molecular genetic analyses of KIT and PDGFRA genes

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 x 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.

Primary small cell carcinoma of the pleura: a case report with immunohistochemical and molecular genetic analyses of KIT and PDGFRA genes

“…The present study is the first report demonstrating positive KIT and PDGFRA and no mutations of KIT and PDGFRA genes in pleural small cell carcinoma. Similar findings have been reported in extrapulmonary small cell carcinoma in mediastinum [4], urinary bladder [5], and pleura [27]. These findings suggest that extrapulmonary small cell carcinoma expresses KIT and PDGFRA proteins, but has no mutations of KIT and PDGFRA genes.…”

“…The present case also exhibited no PDGFRA mutations. PDGFRA protein expression has not been reported in SCLC, but has been reported in extrapulmonary small cell carcinomas, which identified no mutations [4,5,27]. The present case showed a moderate expression of PDGFRA, suggesting that a small amount of PDGFRA is present in small cell carcinoma of the pleura.…”

“…Like small cell lung carcinoma (SCLC), small cell carcinoma of the pleura shows aggressive biological behavior and the prognosis is poor [1][2][3]. However, KIT and platelet-derived growth factor receptor-a (PDG-FRA) have not been examined in extrapulmonary small cell carcinoma except for the author's recent reports of mediastinal and bladder small cell carcinoma [4,5].…”

Amelanotic malignant melanoma of the esophagus: Report of two cases with immunohistochemical and molecular genetic study of KIT and PDGFRA

“…An immunohistochemical analysis was performed, using Dako's Envision method, as previously described [25][26][27][28][29][30] . Genetic analyses of the KIT gene (exons 9, 11, 13 and 17) and the PDGFRA gene (exons 12 and 18) were performed by the PCR direct sequencing method, as previously reported [31][32][33][34][35] . The exons of both genes were selected because they are frequent mutation sites [16][17][18][19][20][21] .…”

Mediastinal small cell carcinoma: a unique clinical entity?

“…These are extremely rare carcinomas, usually manifesting much less aggressive biological behavior and generally good prognosis [10][11][12][13]. In contrast, the SCLC is associated with poor prognosis.…”