This is because up to 92% of NF cases have a specific type of fusion gene in their tumor cells. Fusion genes are abnormal and potentially tumor-inducing genes formed by mergers between parts of two different genes. The fusion gene involved in NF merges part of the USP6 gene to a part of any one of numerous other genes. The USP6 gene is responsible for producing ubiquitin carboxyl-terminal hydrolase 6a, a deubiquitinating enzyme that indirectly regulates various signaling pathways which regulate cell growth and death. All of the USP6-containing fusion genes overproduce a chimeric protein (i.e. an abnormal protein consisting of parts derived from different genes) with uncontrolled deubiquitinating enzyme activity that is thought to contribute to the development of NF. Presentation
Nodular fasciitis occurs in all age groups but more often affects 20-40 year old individuals. Males and females are equally affected. NF tumors, which may be tender or painful, typically present as rapidly growing solitary lesions that reach a final size (usually of 2–3 cm.) within a few weeks. They are located in the upper limbs (39–54% of cases), trunk (15–20% of cases), lower limbs (16–18% of cases), and head or neck area (20% of cases). (Involvement of the head or neck area is more commonly observed in children.) Rare cases off NF have occurred in the: 1) joints of the knee (18 cases), shoulder (3 cases), hand (3 cases), elbow (2 cases), hip (1 case), ankle (1 case), and temporomandibular joint (1 case); or 2) peripheral nerves of the arm (i.e.
Hidradenoma refers to a benign adnexal tumor of the apical sweat gland. These are 1–3 cm translucent blue cystic nodules. It usually presents as a single, small skin-colored lesion, and may be considered closely related to or a variant of poromas. Hidradenomas are often sub-classified based on subtle histologic differences, for example:
Eccrine acrospiroma
Clear-cell hidradenoma or acrospiroma
Nodular hidradenoma or acrospiroma
Solid-cystic hidradenomaDiscussion of sweat gland tumors can be difficult and confusing due to the complex classification and redundant terminology used to describe the same tumors. For example, acrospiroma and hidradenoma are synonymous, and sometimes the term acrospiroma is used to generally describe benign sweat gland tumors. In addition, a single lesion may contain a mixture of cell-types. There has also been a change in understanding about how tumors that were previously believed to strictly derive from specific sweat gland types may, in fact, derive from both eccrine or apocrine glands.Hidradenomas are by definition benign, with malignant transformation very rare. When tumors show malignant characteristics, they are known as hidradenocarcinoma. Surgical excision is usually curative and local recurrences are rare, although malignant tumors may metastasize. See also
Spiroma
List of cutaneous conditions
List of cutaneous neoplasms associated with systemic syndromes

References


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