2020 Volume 59 Issue 6 Pages 279-285
Background : Perivascular epithelioid cell tumors (PEComas) are rare neoplasms that can develop in any organ.
Case : A woman in her 60 s underwent right upper lobectomy for four tumors in the right upper lobe, and also partial resection for a tumor in the left lower lobe. One of the four tumors in the right upper lobe was diagnosed by preoperative fine needle aspiration cytology as being an adenocarcinoma. The left lung lower lobe tumor was diagnosed intraoperatively, by frozen section examination and stamp cytology, as being “different from adenocarcinoma.” Macroscopically, this latter tumor, measuring 1.0×1.0×0.7 cm in size, was a well-circumscribed solid tumor, with a grayish-white cut surface. Cytologic examination indicated some atypical cell clusters, with the cells containing ill-defined clear-to-granular eosinophilic cytoplasm, and nuclei with occasional intranuclear cytoplasmic inclusions, fine granular chromatin and small nucleoli. Histologically, the tumor was composed of solid and well-defined cell nests showing a positive Periodic acid Schiff (PAS) reaction, and positive immunohistochemical staining for Human Melanin Black 45 (HMB45) and Melan A in about 30% of the tumor cells. Therefore, this tumor was diagnosed as a PEComa (clear cell tumor).
Conclusion : The PEComa had been diagnosed as a tumor “different from adenocarcinoma” intraoperatively, so that misdiagnosis as a metastatic carcinoma was avoided. In such a case, it is important not to overestimate the condition as a more advanced stage of carcinoma.
