Nodular fasciitis (NF) is a benign, soft tissue tumor composed of myofibroblasts (i.e. immature cells that contain features of myocytes and fibroblasts) that typically occurs in subcutaneous tissue (i.e. lowermost layer of the skin), fascia (i.e. band  of connective tissue just beneath the skin), and/or muscles. The literature sometimes titles rare NF variants according to their tissue locations. The most frequently used and important of these are: cranial fasciitis (NF variants that occur in the soft and hard tissues of the skull) and intravascular fasciitis (NF variants that involve arteries and/or veins). In 2020, the World Health Organization classified nodular fasciitis as in the category of benign fibroblastic/myofibroblastic tumors. NF is the most common of the benign fibroblastic proliferative tumors of soft tissue and exceeds in frequency any other tumor or tumor-like lesion in this group of tumors.Nodular fasciitis is a rapidly growing, usually self-limiting neoplasm that occurs primarily but not exclusively in adults. Due to its rapid growth, NF has often been misdiagnosed as a malignant tumor, usually a sarcoma. Indeed, NF was originally termed subcutaneous pseudosarcomatous fibromatosis when first described in 1955 by Konwaler et al. The correct diagnosis of a tumor as NF is pivotal to prevent its overtreatment as a more aggressive and/or malignant growth.NF tumors have long been mentioned as local reactions to traumatic injuries in at least some cases. While it still may be precipitated by such injuries, recent studies indicate that NFs are true neoplasms (i.e. abnormal proliferations of cells even after any precipitating event is removed).
Nijmegen breakage syndrome (NBS) is a rare autosomal recessive congenital disorder causing chromosomal instability, probably as a result of a defect in the double Holliday junction DNA repair mechanism and/or the synthesis dependent strand annealing mechanism for repairing double strand breaks in DNA (see Homologous recombination).NBS1 codes for a protein (nibrin) that has two major functions: (1) to stop the cell cycle in the S phase, when there are errors in the cell DNA (2) to interact with FANCD2 that can activate the BRCA1/BRCA2 pathway of DNA repair. This explains why mutations in the NBS1 gene lead to higher levels of cancer (see Fanconi anemia, Cockayne syndrome.) The name derives from the Dutch city Nijmegen, where the condition was first described.Most people with NBS have West Slavic origins. The largest number of them live in Poland. Presentation
It is characterized by microcephaly, a distinct facial appearance, short stature, immunodeficiency, radiation sensitivity and a strong predisposition to lymphoid malignancy. NBS is caused by a mutation in the NBS1 gene. Unsurprisingly, many of the features are similar to ataxia telangiectasia (AT) and this syndrome was sometimes termed AT-variant 1, as the protein mutated in AT, ATM, interacts with the MRE11/RAD50/NBS1 (MRN) complex. Other syndromes with clinical features similar to Nijmegen Breakage Syndrome include RAD50 deficiency and Cernunnos/NHEJ deficiency. Cause
NBS is caused by a mutation in the NBS1 gene, located at human chromosome 8q21. The disease is inherited in an autosomal recessive manner.