A dermatofibroma, or benign fibrous histiocytomas, is a

benign Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...

nodule in the skin, typically on the legs, elbows or chest of an adult. It is usually painless. It usually ranges from 0.2cm to 2cm in size but larger examples have been reported. It typically results from mild trauma such as an insect bite. Risk factors for developing multiple dermatofibromas include lupus,

HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...

blood cancer Tumors of the hematopoietic and lymphoid tissues (American English) or tumours of the haematopoietic and lymphoid tissues (British English) are tumors that affect the blood, bone marrow, lymph, and lymphatic system. Because these tissues are all ...

and some medicines that weaken immunity. It is usually diagnosed by its appearance, but a biopsy may be required. Other bumps such as

granular cell tumor Granular cell tumor is a tumor that can develop on any skin or mucosal surface, but occurs on the tongue 40% of the time. It is also known as Abrikossoff's tumor, granular cell myoblastoma, granular cell nerve sheath tumor, and granular cell schw ...

, melanoma, clear cell acanthoma and dermatofibrosis lenticularis disseminata may look similar. Usually no treatment is needed. It can remain unchanged for years but can resolve spontaneously.

Signs and symptoms

Dermatofibromas are hard solitary slow-growing

papule A papule is a small, well-defined bump in the skin. It may have a rounded, pointed or flat top, and may have a dip. It can appear with a stalk, be thread-like or look warty. It can be soft or firm and its surface may be rough or smooth. Some h ...

s (rounded bumps) that appear in a variety of colours, usually brownish to tan. They are often elevated or

pedunculated A peduncle is an elongated stalk of tissue. Sessility is the state of not having a peduncle; a sessile mass or structure lacks a stalk. In medicine, a mass such as a cyst or polyp is said to be ''pedunculated'' if it is supported by a peduncle ...

. A dermatofibroma is associated with the

dimple sign The dimple sign or Fitzpatrick's sign is a dermatological sign in which lateral pressure on the skin produces a depression. It is associated with dermatofibroma A dermatofibroma, or benign fibrous histiocytomas, is a benign nodule in the skin, ty ...

; by applying lateral pressure, there is a central depression of the dermatofibroma. Although typical dermatofibromas cause little or no discomfort,

itching Itch (also known as pruritus) is a Wikt:sensation, sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to be classified as any one type of Sensory system, sensory experience. Itch has many similarities to pain, ...

and tenderness can occur. Dermatofibromas can be found anywhere on the body, but most often they are found on the legs and arms. They occur more often in women; the male to female ratio is about 1:4. The age group in which they most commonly occur is 20 to 45 years. Some physicians and researchers believe dermatofibromas form as a reaction to previous injuries such as insect bites or thorn pricks. They are composed of disordered collagen laid down by

fibroblasts A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework ( stroma) for animal tissues, and plays a critical role in wound healing. Fibroblasts are the most common cells ...

. Dermatofibromas are classed as benign skin lesions, meaning they are completely harmless, though they may be confused with a variety of subcutaneous tumours. Deep penetrating dermatofibromas may be difficult to distinguish, even histologically, from rare malignant fibrohistocytic tumours like

dermatofibrosarcoma protuberans Dermatofibrosarcoma protuberans (DFSP) is a rare locally aggressive malignant cutaneous soft-tissue sarcoma. DFSP develops in the connective tissue cells in the middle layer of the skin (dermis). Estimates of the overall occurrence of DFSP in the ...

. Dermatofibromas typically have a positive ''buttonhole sign'', or central dimpling in the center.

Signs and symptoms

Diagnosis

Immunohistochemical staining

See also

References

External links