Further studies are needed to determine which, if any, of these pathways are overactive in and can be successfully targeted with specific drug therapies to treat NF and its variants.Two cases of NF have tumor cells in which the USP6 gene has fuses with the  PPP6R3 (i.e. protein phosphatase 6 regulatory subunit 3) gene. In both of these cases, the tumors clearly showed malignant behavior. Diagnosis
NF may resemble and therefore be misdiagnosed as dermatofibrosarcoma protuberans, fibrosarcoma, malignant fibrous histiocytoma, spindle-cell melanoma (a rare form of melanoma,) leiomyosarcoma, and inflammatory myofibroblastic tumor. The diagnosis of NF and its variants depends on a combination of findings no single one of which is definitive. These findings are: the tumors: presentation (particularly its location in the cranium, within blood vessels, or outside of these areas); histopathology (particularly analyses of tumor cell mitoses which if atypical strongly suggest the tumor is not NF); presence of myofibroblasts that typically express muscle-specific actin, SMA, and vimentin and may express CD68 but generally do not express S100, desmin, trypsin, factor VIII, F4/80, or CD34 (lack of Cd34-expressing cells indicates that the tumor is not a sarcoma); and presence of typical neoplastic cells expressing an USP6-containing fusion gene. (USP6-containing fusion genes also occur in the tumor cells of aneurysmal bone cysts, fibroma of tendon sheaths, giant cell reparative granuloma, and myositis ossificans/fibro-osseous pseudotumor of digits.)
A casting defect is an undesired irregularity in a metal casting process. Some defects can be tolerated while others can be repaired, otherwise they must be eliminated. They are broken down into five main categories: gas porosity, shrinkage defects, mould material defects, pouring metal defects, and metallurgical defects. Terminology
The terms "defect" and "discontinuity" refer to two specific and separate things in castings. Defects are defined as conditions in a casting that must be corrected or removed, or the casting must be rejected. Discontinuities, also known as "imperfections", are defined as "interruptions in the physical continuity of the casting". Therefore, if the casting is less than perfect, but still useful and in tolerance, the imperfections should be deemed "discontinuities". Types
There are many types of defects which result from many different causes. Some of the solutions to certain defects can be the cause for another type of defect.The following defects can occur in sand castings. Most of these also occur in other casting processes. Shrinkage defects
Shrinkage defects 
can occur when standard feed metal is not available to compensate for shrinkage as the thick metal solidifies. Shrinkage defects will have jagged or linear appearance. Shrinkage defects usually occur in either the cope or drag portion of the casting. Shrinkage defects can be split into two different types: open shrinkage defects and closed shrinkage defects. Open shrinkage defects are open to the atmosphere, therefore as the shrinkage cavity forms, air compensates. There are two types of open air defects: pipes and caved surfaces.