Other benign dermal tumours
These benign tumours are firm discrete usually solit-ary dermal nodules (Fig. 18.55), often on the extremities of young adults.
The lesions have an ‘iceberg’ effect in that they feel larger than they look. The over-lying epidermis is often lightly pigmented and dimples when the nodule is squeezed. Some lesions seem to follow minor trauma or an insect bite. Histologically, the proliferating fibroblasts merge into the sparsely cellular dermis at the margins. A straightforward lesion may be left alone but, if there is any diagnostic doubt, it should be excised.
solitary tumours occur occasionally, multiple neurofibromas are most common and
are usually seen as part of the inherited condition of neurofibromat-osis.
This rare benign tumour is usually solitary. It may appear spontaneously but is seen most often as a result of nerve injury at the site of trauma or a surgical wound. There is nothing specific about the appear-ance of the skin-coloured dermal nodule but the tumour is frequently painful, even with gentle pressure. ENGLAND is a useful acronym for painful tumours (Eccrine spiradenoma, Neuroma, Glomus tumour,
Leiomyoma, Angiolipoma, Neurofibroma (rarely) and Dermatofibroma (rarely) ).
This is an overgrowth of dense fibrous tissue in the skin, arising in response to trauma, however trivial. The tendency to develop keloids is genetically inher-ited. Keloids are common in Negroids and may be familial. Keloid formation is encouraged by infection, foreign material and by wounds (including surgical ones) especially those not lying along the lines of least tension or the skin creases. Even in Caucasoids, keloids are seen often enough on the presternal area, the neck, upper back and deltoid region of young adults to make doctors think twice before removing benign lesions there. Silicone sheeting and intrale-sional steroid injections are helpful but treatment should be given early, preferably for developing lesions.
Lipomas are common benign tumours of mature fat cells in the subcutaneous tissue. There may be one or many (Fig. 18.56) and lipomas are rarely a familial trait. They are most common on the proximal parts of the limbs but can occur at any site. They have an irregular lobular shape and a characteristic soft rub-bery consistency. They are rarely painful. They need to be removed only if there is doubt about the dia-gnosis or if they are painful or unsightly.
This term describes the various conditions in which the skin, and occasionally other tissues, contains an excess of mast cells. All types are characterized by a tendency for the skin to wheal after being rubbed. The main types are as follow.
• Mastocytoma. Usually presents as a solitary pink orbrown itchy papule which wheals on rubbing. There are no systemic features.
• Juvenile mastocytosis. This is the most commontype. Numerous pink or brown papules develop over the trunk and limbs (Fig. 18.57). There is no systemic involvement, and the condition is often mistaken for multiple melanocytic naevi.
• Diffuse cutaneous mastocytosis. This is rare and seenmostly in infants, being characterized by persistent dermographic wheals that appear after minor friction. The skin is diffusely infiltrated with mast cells, pro-ducing a thickened appearance like pigskin. The bone marrow, liver and spleen may be involved. Flushing is common. Death from massive histamine release is a real risk. Spontaneous improvement usually occurs.
Adult type. Pink or pink-brown telangiectatic mac-ules appear in early adult life and can spread to cover the whole body. The liver, spleen and bone are involved in up to 20% of cases but systemic features such as headaches, flushing and palpitations are unusual.