Cutaneous spindled follicle center cell lymphoma with abundant mucin: A diagnostic pitfall

Primary cutaneous follicle center cell lymphoma is the most prevalent type of primary cutaneous B-cell lymphoma and usually portends a favorable prognosis. Typically, the diagnosis can be rendered based on characteristic histopathologic features and immunohistochemical profile. Rarely, a diagnostically challenging variant with a predominant spindle morphology mimicking other malignant spindle cell neoplasms may be encountered. Even more unusual is the presence of a prominent myxoid stroma in this rare sarcomatoid variant of follicle center cell lymphoma. Herein, we present a case of a 52-year-old man with a slowly enlarging cyst-like lesion on the chin with histopathologic examination revealing a malignant, predominantly spindled neoplasm within an abundant myxoid stroma. Following a broad panel of immunohistochemical stains, the strong positive staining of the spindle cells for LCA (CD45), CD20, and Bcl-6 confirmed the diagnosis of follicle center cell lymphoma. We present this distinctive rare subtype of cutaneous follicle center cell lymphoma to increase awareness of this variant and to discuss challenging histopathologic mimics to consider while highlighting the utility of immunohistochemistry stains to avoid misdiagnosis.