Contributed by Bruce D. Leckey Jr. DO, Ivy John, MD
A female in her 50's with a known history of neurofibromatosis type 1 since childhood, and a number of previously resected neurofibromas, presented with an enlarging right flank mass concerning for a plexiform neurofibroma. A computed tomography (CT) abdomen and pelvis with contrast demonstrated a cystic mass measuring up to 7.4 cm within the right abdominal wall (Figure 1, A) with areas of calcification and enhancement.
Gross examination revealed a yellow-white to gray-yellow, firm, poorly defined, focally calcified, and focally cavitated to grossly necrotic (30%) mass measuring up to 15.2 cm.
The flank mass was subsequently resected and demonstrated features of diffuse-type neurofibroma, including cellular proliferation of bland spindled cells expanding the dermis, entrapping adnexal structures, and permeating the subcutis (Figure 2, A) with prominent back to pseudomeissnerian corpuscles (Figure 2, B). In areas, the tumor transitioned into more cellular areas with increased cytologic atypia and mitotic activity (Figure 2, C), and then finally into highly cellular areas composed of cellular fascicles of spindle cells with alternating hyper and hypocellular areas with perivascular accentuation, geographic necrosis and frequent mitoses (21/10 HPF) (Figure 2, C). Immunohistochemistry demonstrated that the neoplastic cells were positive for CD34, patchy positive for S100 (Figure 3, A) and SOX10 (nuclear), and negative for H3K27me3 (abnormal) (Figure 3, B), cytokeratin AE1/AE3, SMA, and desmin.