Localized tenosynovial giant cell tumor (TGCT) usually occurs in the hand and foot regions. However, localized TGCT with extensive cartilaginous metaplasia is rare, especially in the tendon sheath of the toe. Here, we report a case of localized TGCT with cartilaginous metaplasia in a 57-year-old man. The tumor presented as a lobular mass measuring 2.2 cm in its greatest dimension and arose in the flexor digitorum tendon sheath of the right 2nd toe. Clinically, the mass was palpable 1 year ago and brought pain during walking. Microscopically, the mass was composed of focal conventional TGCT and cartilaginous components. The conventional TGCT areas consisted of mononuclear cells, multinucleated giant cells, and hemosiderin deposition. The chondroid areas were extensive and comprised more than 90% of the whole tumor. In this case, the mononuclear cells in the conventional TGCT areas showed focal immunohistochemical staining for podoplanin and S100 protein as well as diffuse staining for CD68, which is consistent with the staining pattern of conventional TGCT. The mononuclear cells in the chondroid areas were focal positive for podoplanin and diffuse positive for S100 protein. Chondroid metaplasia in diffuse TGCT has been reported in 10 cases involving the temporomandibular, elbow, and hip joints. However, there has been no report of a localized form of chondroid TGCT involving an extra-articular region.

This report describes a rare case of primary rectal mature teratoma in a 56-year-old woman. She was referred to the outpatient clinic with a large pedunculated rectal mass, which was found during a regular health check-up. Polypectomy was performed and microscopic findings showed various structures derived from all three germ cell layers. Epidermis, hair follicles, sebaceous glands, eccrine glands, and apocrine sweat glands, with some scattered melanophages and lymphocytes were present as ectodermal derivatives. Smooth muscle fibers, blood vessels, and fibrous and adipose tissues were found as mesodermal derivatives. In addition, thyroid follicles, mucinous glands, and bronchial respiratory epithelium with peribronchial glands were detected as endodermal derivatives. She is healthy and has shown no evidence of recurrence or distant metastasis for 25 months post-surgical resection. Primary rectal teratomas are generally benign and primarily affect women. Therefore, minimally invasive surgical procedures, such as endoscopic polypectomy for a pedunculated polyp and segmentectomy for a larger mass, are satisfactory in most cases. Induction of primary rectal teratomas has been suggested to occur mainly by errors in a single germ cell after the end of meiosis I; in addition, it has also been suggested that the difference in gender incidence may be associated with differences in sex chromosomes between males and females rather than with anatomical proximity between ovary and rectum.

Malignant transformation of mature cystic teratoma (MCT) is rare. Sarcomatoid carcinoma is a neoplasm comprising malignant mesenchymal cells and a conventional carcinomatous area. Here, we report on a case of sarcomatoid carcinoma arising from an MCT in the left ovary of a 45-year-old female. A unilocular cyst consistent with MCT was observed; however, a nodule within the cyst was confirmed from the resected ovary. Microscopically, the nodule showed both squamous cell carcinoma and pleomorphic sarcomatous components admixing with each other. Lining epithelial cells at the periphery of the main tumor showed squamous metaplasia. When a sarcomatous component is observed in the ovary tumor, it is important to find a squamous cell component, either benign or malignant.