Apocrine adenocarcinoma arising from mature cystic teratoma in the anterior mediastinum: A case report.

Primary mediastinal apocrine adenocarcinoma is extremely rare, with only one case reported to date. Here, we report a surgical case of primary mediastinal apocrine adenocarcinoma. An anterior mediastinal cystic tumor with calcification was identified on chest computed tomography scan in a 51-year-old female patient undergoing maintenance hemodialysis. The tumor was 19 mm in size, did not invade the adjacent organs or show distant metastases, and was surgically removed. Microscopic examination revealed that the tumor cells exhibited cribriform or solid proliferation patterns with thick fibrous capsules. The tumor cells had an abundant eosinophilic cytoplasm, and decapitation secretion was noted. Immunohistochemistry revealed positivity for GCDFP-15 and androgen receptors, with Ki-67 positivity at 10%. The cyst wall exhibited extensive fibrosis and keratinized material, with bone and bronchial glands identified at the cyst periphery; the tumor cells were contiguous with those structures. The patient was diagnosed with apocrine adenocarcinoma arising from a mature cystic teratoma. The patient has maintained a recurrence-free status without adjuvant therapy for 6 years after surgery. This case presents a small primary mediastinal apocrine adenocarcinoma that achieved remarkable long-term survival.