Published online Jan 28, 2015. doi: 10.3748/wjg.v21.i4.1349
Peer-review started: May 26, 2014
First decision: July 9, 2014
Revised: July 18, 2014
Accepted: September 12, 2014
Article in press: September 16, 2014
Published online: January 28, 2015
Processing time: 249 Days and 3.7 Hours
A 4-mo history of both epigastralgia and back pain was presented in a 39-year-old male. Computed tomography showed right lung nodule and abdominal mass attached to the gastric wall, measuring approximately 30 mm and 70 mm in diameter. Since biopsy samples from the lung and abdomen revealed poorly differentiated adenocarcinoma and malignant tumor, clinicians first interpreted the abdominal mass as metastatic carcinoma, and a right lower lobectomy with following resection of the mass was performed. Gross examination of both lesions displayed gray-whitish to yellow-whitish cut surfaces with hemorrhagic and necrotic foci, and the mass attached to the serosa of the lesser curvature on the gastric body. On microscopic examination, the lung tumor was composed of a proliferation of highly atypical epithelial cells having abundant eosinophilic cytoplasm, predominantly arranged in an acinar or solid growth pattern with vessel permeation, while the abdominal tumor consisted of sheets or nests with markedly atypical epithelioid cells having pleomorphic nuclei and abundant eosinophilic to clear cytoplasm focally in a radial perivascular or infiltrative growth pattern. Immunohistochemically, the latter cells were positive for HMB45 or α-smooth muscle actin, but the former ones not. Therefore, we finally made a diagnosis of malignant perivascular epithelioid cell tumor (PEComa) arising in the gastric serosa, combined with primary lung adenocarcinoma. Furthermore, small papillary carcinoma of the thyroid gland was identified. The current case describes the coincidence of malignant PEComa with other carcinomas, posing a challenge in distinction from metastatic tumor disease.
Core tip: We reported the first single-case of malignant perivascular epithelioid cell tumor (PEComa) arising in the gastric serosa, combined with primary lung adenocarcinoma of poorly differentiated type. It is likely that the present malignant PEComa might pose a challenge in distinction from metastatic lung carcinoma on the examination of the small inadequate biopsy specimen. Pathologists should be aware that its characteristic features could lead to a misdiagnosis especially in this case. Furthermore, we suggest that a large panel of antibodies including various melanocytic, muscle or epithelial markers in immunohistochemistry should be useful and critical aids for reaching the correct diagnosis of malignant PEComa.