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Case Reports

Abstract

Skin fibroma and its variants represent a rare subset of cutaneous fibromas that can manifest sporadically or in association with Cowden syndrome (CS). Giant cell collagenoma (GCC) shares similarities with sclerotic fibroma but includes distinctive features such as floret-type giant cells. In this case, we describe a 15-year-old with no significant medical history who presented with a solitary scalp nodule. Upon excision, the tissue revealed a fibroblastic tumor characterized by a sclerotic and whorled collagen pattern, along with multinucleated and floret-like giant cells, and dendritic spindle cells. CD34 positivity was noted, along with focal myxoid change. The PTEN immunohistochemistry showed loss of nuclear staining. The differential diagnosis for such histology includes giant cell fibroblastoma, NTRK-rearranged fibroma, and multinucleate cell angiohistiocytoma. Negative FISH testing for COL1A1::PDGFB and comprehensive immunohistochemical analysis confirmed the diagnosis of GCC. Recent reports associating GCC cases with CS suggest that diagnosing GCC could uncover previously undiagnosed CS. Even when GCC presents as a solitary lesion, it may warrant further investigation and screening for CS, although our patient did not exhibit any CS-related symptoms. The absence of PTEN staining in this biopsy prompts consideration of whether an undiagnosed CS is implicated or if this represents a sporadic mutation. This underscores the importance of molecular genetic testing in asymptomatic patients with GCC. Additionally, the presence of a myxoid component in this lesion expands histologic features of GCC. In conclusion, we aim to contribute to the limited literature on GCC, highlighting its morphological and histological characteristics and their clinical significance.