Cellular Neurothekeoma: Ultrastructural Features and Comparison with Plexiform Fibrohistiocytic Tumor
J Hicks, E Wartchow, J Barrish, SH Zhu, L Goin, J Schrieber, G Mierau. Texas Children's Hospital & Baylor College of Medicine, Houston, TX; The Children's Hospital, Aurora, CO
Background: Cellular neurothekeoma (CNK) is a benign cutaneous neoplasm that affects children and young adults and occurs in the upper extremity, and head and neck. Similarly, plexiform fibrohistiocytic tumor (PFHT) is a cutaneous tumor affecting children and young adults in a similar pattern. In contrast, PFHT tends to recur locally and has metastatic potential (low-grade malignancy). CNK and PFHT share certain histopathologic and immunocytochemical features, leading to difficulty in separating a benign (CNK) tumor from a low-grade malignancy (PFHT).
Design: Patient population consisted of 6 children with CNK (4F:2M, age range 2-10 yrs) and 6 children with PFHT (4F:2M, age range 4 mos-8 yrs). Sites of involvement were similar for CNK and PFHT (upper extremities, head, neck). Tissue was available for light microscopic and electron microscopic examination.
Results: CNK and PFHT shared similar histopathologic features with a plexiform architecture, and a mixture of spindled, epithelioid and "histiocytoid" cells. Occasional osteoclastic cells were noted with both CNK and PHFT. Mitotic activity was variable with both CNK and PFHT ranging from 1 to 22 per HPF. In cases where immunocytochemistry could be performed (CNK=5, PFHT=3), the immunophenotype was similar with positivity for vimentin, focal SMA, focal S100 and focal NSE. Electron microscopy demonstrated certain distinct, distinguishing differences between CNK and PFHT. CNKs were composed of epithelioid and spindled cells with occasional intercellular junctions. The spindle cell population had thin cell processes. CNK cells were surrounded by a thick moderately electron dense basal lamina material that separated the cells from each other. PFHTs were comprised of spindled to ovoid cells with a population of "histiocytoid" cells containing frequent lysosomal granules with "zebra body"-like inclusions, mimicking metabolic storage material. There was also a population of plump spindle cells with prominent endoplasmic reticulum, peripheral cytoplasmic filaments and discontinuous external lamina.
Conclusions: CNK and PFHT have very similar histopathologic and immunocytochemical features, although CNK is a benign tumor and PFHT is a malignant tumor that may metastasize to regional nodes or distant sites. Electron microscopic examination of these very similar tumors allows appropriate classification of these tumors and provides for appropriate management and follow-up.
Wednesday, March 24, 2010 9:30 AM
Poster Session V # 262, Wednesday Morning