Context: The sex cord-like variant of endometrioid carcinoma of the ovary shows many similarities to Sertoli-Leydig cell tumor and granulosa cell tumor. However, few cases of the granulosa cell tumor-like variant have been reported, suggesting this tumor might often be hidden under the diagnosis of granulosa cell tumor.
Objective: To investigate the similarities and differences between the granulosa cell tumor-like variant of endometrioid carcinoma and granulosa cell tumor of the ovary and to evaluate a newly observed feature, namely, nuclear clearing (or optically clear nuclei), in this variant tumor.
Design: A comparative macroscopic, cytologic, histopathologic, and immunohistochemical study in specimens obtained from the following patients: 1 patient with granulosa cell tumor-like variant of endometrioid carcinoma diagnosed by frozen section examination, 3 patients with granulosa cell tumor, and 6 patients with classic endometrioid carcinoma.
Results: The granulosa cell tumor-like variant showed close macroscopic, cytologic, and microscopic similarities to granulosa cell tumor. However, the 2 tumors could be differentiated immunohistochemically. The former also showed intense staining for progesterone receptors and contained nonmorular nests that exhibited the so-called nuclear clearing with biotin activity.
Conclusion: Because the granulosa cell tumor-like variant is pathologically similar to granulosa cell tumor, showing only some dissimilarities to the latter, it can easily be misdiagnosed if the possibility of this variant is not kept in mind. Identification of the typical endometrioid histologic features or related lesions or immunohistochemistry may lead to a proper diagnosis. The observation of nuclear clearing with biotin activity in nonmorular nests suggests that this tumor has endometrioid epithelial characteristics.