Calcifying ghost cell odontogenic tumor (CGCOT) with predominance of clear cells: a case report with important diagnostic considerations.

An 18-year-old female reported painful swelling in the left maxillary region 4 months after the extraction of tooth #15. Because incisional biopsy suggested ameloblastoma with clear-cell changes, segmental resection was performed. The microscopic examination of the excised tissue revealed histomorphologic diversity, with features of typical calcifying ghost cell odontogenic tumor (CGCOT) and a significant clear-cell component constituting more than 50% of the tumor mass without any features of malignancy. Clear cells were periodic acid-Schiff (PAS) positive and mucicarmine negative. CK19 was strongly positive in the solid tumor islands and variably positive in clear cells. A definitive diagnosis of CGCOT with predominance of clear cells was confirmed. Because both squamous metaplasia and clear-cell components were present in the ameloblastic follicles independent of each other, the presence of abundant calcifications favored the diagnosis of CGCOT with a clear-cell component over that of an ameloblastoma with clear-cell changes. The importance of identifying the histomorphologic features of the 2 entities, ameloblastoma and CGCOT, is highlighted. This appears to be the second case reported in the literature, to the best of our knowledge.