## 4 Discussion  
OLGCs are multinucleated cells with abundant cytoplasm that resemble osteoclasts [5]. OLGCs have been described as characteristic features of giant cell tumor of the tendon sheath and giant cell tumor of soft tissue, although they have also been described in other  
Figure 2: (**A**) Low magnification showing a dermal-based lesion with minimally-infiltrative margins (hematoxylin and eosin; original magnification 40\(\times\)); (**B**) lesion shows focal extension to the subcutaneous adipose tissue (hematoxylin and eosin; original magnification 100\(\times\)); (**C**) diffuse granular cell morphology (large-sized cells with large, clear to weakly eosinophilic, granular cytoplasm, and mildly hyperchromatic nuclei with inconspicuous nucleoli) is seen (hematoxylin and eosin; original magnification 200\(\times\)); (**D**) areas with conventional morphology of cutaneous fibrous histiocytoma are focally found (hematoxylin and eosin; original magnification 100\(\times\)). (**E**) Mild thickening and basal layer hyperpigmentation of the overlying epidermis are seen (hematoxylin and eosin; original magnification 250\(\times\)). (**F**) Granular cells are not stained with anti-S100 protein antibody (immunoperoxidase; original magnification 200\(\times\)). cutaneous diseases such as dermic nevi and pilomatrixoma [5,6]. The diagnostic and prognostic significance of the presence of OLGCs is currently unknown. As it has already been described in few case reports found in literature, CFH with OLGCs is a very unusual variant, exhibiting the following histologic features: (i) siderophages and hemosiderin deposits; (ii) OLGCs; (iii) spindle to plump cells with foamy cytoplasm. In our case, the detection of mature bone metaplasia was an additional unusual finding. The first case of ossifying CFH with both OLGCs and ossification was described by [PERSON] and [PERSON] [7] in 1994, while [PERSON] et al. described one of the first cases of CFH with OLGCs in the early 1992 [8]; in addition, [PERSON] and [PERSON] [9] described a rare case of bone formation in CFH without OLGCs, in which there also was a trichoblastic carcinoma/basal cell carcinoma arising on the long standing CFH lesion; [PERSON] et al. [10] described a case of ulcerated CFH with OLGCs in which ossification was only a focal finding. We emphasize that this rare variant of CFH may present OLGCs with or without osseus metaplasia. The importance of recognizing this unusual variant of CFH lays in the differential diagnosis with more aggressive and malignant mimics of CFH such as giant cell variant of malignant fibrous histiocytoma, atypical fibroxanthoma, osteosarcoma, and malignant melanoma [11], as well as with other lesions characterized by the presence of OLGCs such as giant cell tumor of tendon sheath/soft tissue (GCTTS), giant cell reparative granuloma, and brown tumor. The differential diagnosis with giant cell tumor of tendon sheath is problematic because many morphological features are shared by both entities, but the predominance of rounded, synovial-like cells and the location of the lesion almost exclusively on hands and wrists favor the diagnosis of GCTTS. Differential diagnosis with malignant fibrous histiocytoma is usually straightforward because of the pleomorphism, mitoses, and necrotic and haemorrhagic areas that characterize the latter entity. Osteosarcoma, which can also arise as primary cutaneous tumor [12], exhibits malignant cytological features such as malignant osteoid which makes the distinction possible. As mentioned above, another differential diagnosis that needs to be ruled out is the osteogenic melanoma [11], in which malignant melanocytes combined with immature chondro or osteoid matrix, as well as immunohistochemical positivity for S100 protein and HMB45, are typically found. Granular cells are characterized by large cytoplasm filled with intense eosinophilic granules.