Abstract

Superficial CD34 positive fibroblastic tumor (SCPFT) is a recently described low-grade fibroblastic neoplasm of superficial soft tissues that is regarded as a mesenchymal tumor of intermediate malignancy. Characteristic clinical, histologic and immunohistochemical features allow to distinguish these tumors from other entities. All such tumors previously described occur exclusively in a suprafascial location confined to the hypodermis and deep dermis. We describe, for the first time, a low-grade superficial fibroblastic tumor from the right lateral hip of a 50-year-old female, clinically thought to be a hypertrophic scar, with similar morphologic and immunohistochemical features as SCPFT, however, unusually occurring in a more superficial location, mainly involving the superficial to deep dermis with some extension into subcutaneous tissue. Hematoxylin and eosin stained sections showed a patternless proliferation of spindled to polygonal cells, in areas showing marked nuclear pleomorphism with large bizarre vesicular nuclei and prominent nucleoli. Despite the striking pleomorphism, mitoses were rare. Focally, the lesion showed prominent stromal histiocytes and tumor cells with abundant pale eosinophilic and granular cytoplasm as well as cells with xanthomatous change. Immunostains showed the lesional cells to be strongly and diffusely positive for CD34. Expression of INI-1 was retained. AE1/AE3, SMA, desmin, S100 and ERG were negative. Given its unusual appearance, the case was sent for outside expert consultation and was diagnosed as SCPFT. Follow-up was recommended with no recurrence noted after 8 months of initial resection. In conclusion, our case is the first describing a SCPFT centered in the superficial and deep dermis which may require further characterization. Importantly, dermatopathologists should be aware of this new finding to avoid diagnostic pitfalls when evaluating a pleomorphic dermal-based fibroblastic proliferation.

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