Abstract:

Introduction: Myofibroma is a rare spindle-cell neoplasm with a characteristic immunohistochemical staining pattern that includes strong reactivity for smooth muscle actin (SMA). In adults, myofibroma often manifests as a solitary nodule on the head or neck. Case presentation: A 34-year-old man presented with a papule on the cutaneous lip; a 46-year-old female presented with a papule on the nostril; and a 63-year-old female presented with a papule on the nasal ala. The differential diagnoses for these lesions included squamous cell carcinoma, basal cell carcinoma, and verruca vulgaris. Histopathologic examination revealed nodules of bland and monomorphous ovoid spindle cells associated with pericytomatous vessels within a myxoid and collagenous stroma imparting a pseudochondroid appearance. The lesion from the 34-year-old man was positive for CD34 in the spindle cells but only weakly positive for SMA, calponin, and HHF35, and negative for STAT6. The lesion from the 46-year-old woman was positive for CD34, weakly and focally positive for SMA, and negative for STAT6. The lesion from the 63-year-old woman was negative for CD34 in the spindle cells, weakly and focally positive for SMA, and negative for CD10 and CD163. Despite the atypical immunohistochemical appearance, the histomorphologic appearances are typical of myofibroma. Discussion/Conclusion: We describe three cases of myofibroma with centrofacial location and a potentially misleading immunohistochemical profile including weak or absent reactivity with SMA. This series aims to widen the spectrum of immunohistochemical findings observed in myofibroma.

Financial Disclosure:
No current or relevant financial relationships exist.

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John Ahn, MD