Dermatológia pre prax 1/2021

Atypical fibrous histiocytoma of the skin

Background: Benign fibrous histiocytoma (BFH) is a very frequent diagnosis in dermatopathologic practice. In addition to the conventional form, there are several rarer subtypes and variants of BFH, that exhibit different histomorphologic features and may cause diagnostic difficulties. Case report: A 57-year old woman presented with a painless skin tumor arising on the right arm. It appeared as a brownish, slightly elevated and relatively poorly demarcated lesion measuring 1 cm in diameter. Histologically, it was composed of a dense population of dermal spindle and polygonal cells resembling histiocytes and (myo)fibroblasts. Most of them showed a marked pleomorphism with bizzare and monster nuclei. Nevertheless, the mitotic and proliferative activity was low. The tumor focally expressed CD68, Factor XIIIa and alpha-smooth muscle actin. The spectrum of histopathologic findings and immunophenotype confirmed a diagnosis of atypical fibrous histiocytoma. Conclusion: Atypical fibrous histiocytoma is a rare variant of BFH, whose characteristic feature is a marked pleomorphism of tumor cells. Although this finding does not affect a prognosis of disease, it is accompanied by a higher recurrence rate compared with the conventional BFH. In biopsy practice, it is important not confuse it with the tumor entities possessing a malignant potential, and thus to avoid the initiation of a more aggressive treatment strategy.

Keywords: benign fibrous histiocytoma, atypical histiocytoma