Granular Cell (Granular-type) Fibrous Papule of the Face: Case Report and Literature Review Emphasizing Morphologic and Immunohistochemical Pitfalls.

Granular cell (granular-type) fibrous papule is a rare variant of facial fibrous papule/solitary angiofibroma in which lesional stromal cells show prominent cytoplasmic granularity. Because granular cytoplasm is a nonspecific phenotype shared by tumors of diverse lineage, granular-type fibrous papule may be misdiagnosed as granular cell tumor or other granular-cell lesions. We present a case of granular-type fibrous papule in an adult patient, highlight key histopathologic and immunohistochemical findings, and provide a focused review of published cases. In the literature, reported lesions most often occur on the nose and show periodic acid-Schiff-positive diastase-resistant granules with immunoreactivity for lysosomal markers (eg, CD68, NKI/C3) and absence of schwannian markers (S100/SOX10) in cases where these are documented.