Superficial CD34-Positive Fibroblastic Tumor: A Case Report and Review of the Literature.

To the Editor: In 2014, superficial CD34-positive fibroblastic tumor (SCPFT), a mesenchymal neoplasm with intermediate malignancy, was identified by Carter et al.1 As an emerging novel disease entity, SCPFT is under-recognized in the field of dermatology.2 In this article, we present a case of SCPFT and a literature review. A 51-year-old woman presented with a 2-year history of a painful skin-colored subcutaneous tumor measuring 15 mm in diameter on the left thigh (Fig. 1). Skin biopsy revealed an infiltrative tumor composed of ovoid to spindled cells in a fascicular pattern, located in the deep dermis (Fig. 2). The tumor cells displayed granular cytoplasm and nuclear pleomorphism with bizarre, hyperchromatic nuclei, and intranuclear pseudoinclusions (Figs. 3A–D). Mitotic activity was scant, and atypical mitotic figures were not observed. Occasional multinucleated or lipidized tumor cells were identified, and necrosis was not observed. In terms of immunohistochemistry, the tumor cells were strongly positive for CD34 and focal aberrant expression of AE1/AE3 (Figs. 4A, B), focally positive for CD10, and negative for smooth muscle actin and S-100 protein. A diagnosis of SCPFT was established, and marginal excision of the residual tumor was performed. No local recurrence or distant metastasis occurred during the 4 years of follow-up.FIGURE 1.: A skin-colored subcutaneous tumor, about 15 mm in diameter, on the left thigh.FIGURE 2.: A relatively well-circumscribed tumor involving the deep dermis and extending into the superficial subcutis [hematoxylin and eosin (H&E) staining, ×10].FIGURE 3.: A, fascicles of ovoid to spindled tumor cells (H&E staining, ×100). B, Tumor cells show nuclear pleomorphism, with enlarged, bizarre, hyperchromatic nuclei (H&E staining, ×400). C, Tumor cells with abundant granular cytoplasm (H&E staining, ×400). D, Intranuclear pseudoinclusion (arrow) (H&E staining, ×400).FIGURE 4.: A, Diffuse and strong expression of CD34 (original magnification ×100). B, Focal aberrant expression of AE1/AE3 (original magnification ×100).Because SCPFT was first identified in 2014,1 only 38 cases have been reported in English-language literature2–10 (Table 1). In these 38 cases plus our patient, SCPFT usually occurred in young- to middle-aged adults (mean age, 37.7 years) with a slight male predilection (M:F 1.79:1). It presented as an asymptomatic or painful slow-growing mass, ranging in size from 1.5 to 10 cm (mean, 3.7 cm). The preoperative duration was usually more than 1 year. SCPFT may occur anywhere on the body, but most lesions appear on the lower limbs, particularly the thighs. Histopathologically speaking, the tumors were confined to the deep dermis and superficial subcutis. They were composed of fascicles or sheets of epithelioid to spindle cells with abundant granular or glassy eosinophilic cytoplasm and bizarre, hyperchromatic nuclei. Marked pleomorphism but low mitotic activity was noted in all cases. Immunohistochemically speaking, all tumors showed strong CD34 positivity, and approximately half expressed cytokeratins. Endothelial, myogenic, and melanocytic markers were negative. Ultrastructural examination of samples from 2 cases3,8 confirmed fibroblastic differentiation. Positron emission tomography in one case8 showed the abnormal uptake of 2-(18F) fluoro-2-deoxy-d-glucose, with a maximum standardized uptake value of 2.57, which was consistent with its intermediate malignancy. Cytogenetic studies of one case8 disclosed chromosomal translocation of t(2;5)(q31; q31), which was hypothesized to be a specific chromosomal aberration. All patients were treated with surgery. During the mean follow-up period of 6.5 months, no recurrences or metastases occurred, with the exception of one patient1 who developed regional lymph node metastasis 7 years after incomplete excision of the primary lesion.TABLE 1.: Clinical Features and Disease Outcomes of 38 Previously Reported Cases of Superficial CD34-Positive Fibroblastic Tumor and Our PatientTABLE 1-A.: Clinical Features and Disease Outcomes of 38 Previously Reported Cases of Superficial CD34-Positive Fibroblastic Tumor and Our PatientSCPFT must be distinguished from other mesenchymal neoplasms with pleomorphism and low mitotic activity or CD34 positivity. Myxoinflammatory fibroblastic sarcoma differs from SCPFT because it is characterized by a multilobulated architecture with prominent paucicellular myxoid zones and usually shows TGFBR3-MGEA5 translocation.11 Pleomorphic hyalinizing angiectatic tumor has distinctive features such as thick-walled ectatic vessels with prominent perivascular hyalinization. Myxofibrosarcoma exhibits a myxoid multinodular growth pattern, curvilinear thin-walled blood vessels, perivascular tumor cell condensation, and much higher mitotic rates. Both atypical fibroxanthoma and undifferentiated pleomorphic sarcoma/malignant fibrous histiocytoma have brisk mitotic activity and CD34 negativity. Atypical fibrous histiocytoma is usually observed against a background of conventional fibrous histiocytoma and lacks CD34 expression. Both dermatofibrosarcoma protuberans and fibrosarcoma exhibit monomorphic cytology. Malignant granular cell tumor is a relatively monomorphic spindle cell sarcoma with S-100 protein positivity. In conclusion, SPCFT is characterized by marked pleomorphism, an extremely low mitotic rate, and strong CD34 positivity. It behaves as an intermediate malignancy with rare recurrence and metastasis. Recognition of this novel disease entity may help dermatologists to discriminate SPCFT from other potential morphological mimics.