Cellular Fibrous Histiocytoma Presenting as Basal Cell Carcinoma

Dear Sir, Cellular fibrous histiocytoma (CFH) is a rare variant of dermatofibroma and accounts for about 5% of cutaneous fibrous histiocytomas (also known as dermatofibroma).[1] Here, we report a case of CFH with a unique clinical and dermoscopic presentation. A healthy 34-year-old Chinese man presented with a solitary nodule located on his left lateral part of the nose. The lesion emerged as a papule 1 year ago and gradually progressed to a nodule without any pain or itch. The patient received laser therapy to remove the nodule in local hospital. However, a few months later, the nodule relapsed and ulcers appeared. The patient had no skin cancer in both personal and family history. He also denied any trauma of nose before the skin lesion emerged. Physical examination revealed a solitary red or skin-coloured nodule with surface ulcers on the left side of the nose [Figure 1a]. Dermoscopic evaluation displayed numerous proliferated and dilated vessels [Figure 1b].Figure 1: (a), Solitary nodule with surface telangiectasia. (b), Dermoscopic examination of the nodule lesion displayed numerous proliferated and dilated vessels (black arrows)Histopathologic examination showed a well-defined lesion located in the dermis. The overlying epidermis was thin, and focal ulcers were seen. The tumour was composed of spindle cells with a prominent fascicular growth pattern [Figure 2a]. At the periphery of the lesion, tumour cells were surrounded by dermal collagen bundles. Some multinucleated giant cells were observed [Figure 2b]. Immunohistochemical (IHC) staining demonstrated positive for vimentin, CD68, and CD163, focal staining for SMA, but negative for CD34, desmin, and SOX10 [Figure 3a-f]. Based on above findings, a diagnosis of CFH was made. Complete excision was performed, and the tumour did not relapse after 6 months of follow-up.Figure 2: (a), Histopathologic examination shown a well-defined lesion located in the dermis in low power view. (b), Some multinucleated giant cells were observed in high power view (asterisks)Figure 3: Immunohistochemical staining demonstrated positive for vimentin (a), CD68 (b), and CD163 (c) but negative for CD34 (d), desmin (e), and SOX10 (f)CFH is commonly seen in young male adults and favourites the limbs and head and neck area.[2] In contrast to ordinary dermatofibroma, CFH has a feature of high cellularity, limited polymorphism, and a fascicular growth pattern.[3] The lesions of CFH are usually larger than common dermatofibroma and have a high recurrence rate.[1] In our case, the clinical manifestation of solitary nodule with surface ulcers suggested the possibility of basal cell carcinoma (BCC) and melanoma. The dermoscopic examination results of numerous proliferated and dilated vessels supported the diagnosis of BCC. In addition, the dermatologic surgeon performed an extended excision surgery to remove the tumour completely in the outpatient operating room. However, histopathologic examination displayed a well-defined lesion located in the dermis and a mass of spindle cells with a prominent fascicular growth pattern. Many multinucleated giant cells were also observed. The histopathologic outcome was not consistent with BCC and indicated a spindle cell tumour including CFH, dermatofibrosarcoma protuberans (DFSP), leiomyosarcoma, and atypical fibrous histiocytoma (AFH). DFSP is also located in the dermis but commonly shows diffuse irregular infiltration of the subcutaneous fat. The differential diagnosis between CFH and DFSP can be very hard, especially in cases of CFH with a storiform growth pattern and extensive involvement of the subcutaneous tissue. CD34 and CD163 are two reliable markers for distinguishing CFH from DFSP. CFH shows CD163 positive and CD34 negative, while DFSP demonstrates contrary staining with CD34 positive and CD163 negative.[4] The IHC outcomes of our case supported CFH other than DFSP. Distinction between leiomyosarcoma and CFH is easier by the histopathology and IHC. Leiomyosarcoma presents cells with cigar-shaped nuclei, focal cytologic atypia, and uniform fascicular growth pattern. Diffuse positive staining for SMA and desmin is also helpful for distinguishing leiomyosarcoma from CFH. As our case shown focal staining for SMA and negative staining for desmin, leiomyosarcoma was excluded. In addition, AFH should also be included in the differential diagnosis of CFH histologically. The distinctive features of AFH in histology contain a dermal lesion extending into superficial subcutaneous adipose tissue and pleomorphic spindle cells with large and hyperchromatic nuclei. The tumour cells in our case lacked cellular pleomorphism and nuclear atypia; thus, AFH was excluded. At last, the histologic features and negative SOX10 staining of our case also excluded the diagnosis of melanoma. We have reviewed the latest decade literatures about CFH on PubMed [Table 1].[3,5,6] Although CFH is traditionally thought to be a benign condition, regional and distant metastasis have been previously reported in a small number of cases.[6-8] Large tumour size, high cellularity, local recurrence, and aggressive behaviour may be the risk factors of metastasis.[7,9] Therefore, close clinical follow-up after surgery is mandatory.Table 1: Overview of cases of cellular fibrous histiocytoma reported in the literature in recent decade and our caseDeclaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.