myelin-basic-protein and Neuroma

The primary hyperplastic nature of palisaded encapsulated neuromas (PENs) has been recently challenged by suggesting a traumatic origin. We studied eight cases of traumatic neuroma (TN) and 12 cases of PEN by routine light-microscopic, histochemical, and immunohistochemical methods to assess evidence of previous tissue injury. Sections from the formalin-fixed, paraffin-embedded tissue were stained with hematoxylin-eosin, trichrome, elastic, reticulin, Giemsa, colloidal iron (with and without hyaluronidase), and Bielschowsky silver stains. Antibodies were applied to collagen types I, III, and IV, MAC 387, factor XIIIa, alpha 1-antitrypsin (A1AT), epithelial membrane antigen (EMA), Leu-7, and myelin basic protein using ABC techniques. We found that (a) in TN the individual fascicles were usually surrounded by perineurial cells, whereas in PEN the perineurial cells were observed mainly in the capsular areas and only rarely within the fascicles as evidenced by EMA antibodies; (b) histochemically TN contained considerably larger amounts of collagen (types I and III), acidic mucin, and myelin products than did PEN; and (c) neither PEN nor TN contained increased inflammatory cells or cells positive for factor XIIIa, MAC 387, or A1AT. We conclude that (a) there are substantial structural and histochemical differences between TN and PEN, (b) the changes suggest that the classic form of PEN has a different histogenesis than TN, and (c) on histologic grounds, chronic minor trauma could not be excluded as an etiologic factor for PEN.

Topics: alpha 1-Antitrypsin; Antigens, Differentiation; Antigens, Neoplasm; Collagen; Humans; Immunohistochemistry; Membrane Glycoproteins; Mucin-1; Myelin Basic Protein; Neuroma; Skin; Skin Neoplasms; Transglutaminases

Eleven cases of palisaded, encapsulated neuroma (PEN) were studied by routine light microscopic and immunohistochemical methods. PEN showed the following staining reactions: strong, diffuse for S-100 protein (11/11) and collagen Type IV (Col. IV) (11/11); moderately strong, focal for myelin basic protein (MBP) (9/11) and Leu-7 (9/11); weak, focal for MBP (2/11), Leu-7 (2/11), neuron specific enolase (NSE) (4/11), neural filaments (NF) (5/11), epithelial membrane antigen (EMA) (6/11), and negative for glial fibrillary acidic protein (GFAP). Bielschowsky silver stain was positive in 11/11, but only four cases contained numerous axons. Col. IV and EMA stains showed a complete capsule in 1/11, incomplete capsules in 5/11 and no discernible capsules in the remainder. We concluded that (1) the immunologic profile of PEN is not specific; (2) conventional silver stain remains a suitable method to demonstrate axon-like structures; (3) the ratio of axons to Schwann cells is variable and generally less than 1:1, as previously assumed; (4) MBP and Leu-7 coexpression in Schwann cells suggests myelinization of some of the nerve fibers; (5) the pattern of EMA reaction supports perineurial cell involvement in PEN; and (6) despite the current definition of PEN, they are usually not completely encapsulated as evidenced by Col. IV and EMA strains.

Topics: Antigens, Differentiation; Antigens, Neoplasm; CD57 Antigens; Collagen; Glial Fibrillary Acidic Protein; Humans; Immunohistochemistry; Intermediate Filaments; Membrane Glycoproteins; Mucin-1; Myelin Basic Protein; Neuroma; Phosphopyruvate Hydratase; S100 Proteins; Skin Neoplasms