Isolated Pedunculated Collagenoma (Collagen Nevi) of the Scalp

Sir,

Connective tissue nevi of the skin are hamartomatous proliferative lesions consisting chiefly of one of the components of the extracellular matrix, namely, collagen, elastin, or glycosaminoglycans.[1] Connective tissue nevi with predominant collagen and elastic component are referred to as Lipschutz type and Lewandowsky type respectively.[2] Multiple collagenomas are a feature of several distinct diseases and syndromes, including tuberous sclerosis, Buschke-Ollendorf syndrome (dermatofibrosis lenticularis disseminata), eruptive collagenomas, and familial cutaneous collagenoma.[3] Isolated cerebriformcollagenoma of the palm and sole is a well known entity and has been reported in association with Proteus syndrome.[4,5] We hereby report a case of isolated pedunculatedcollagenoma of the scalp for its unusual location and absence of other syndromic features.

A 20-year-old unmarried male presented to our out-patient department with an asymptomatic skin colored mass on the scalp region of three years duration which was gradually increasing in size. The patient did not report any previous history of trauma at the involved area. There was no family history of any cutaneous disorder. Dermatological examination showed a soft skin to pink colored mass on vertex of the scalp and measured about 5 centimeter in diameter. [Figure 1] We considered a differential diagnosis of sebaceous nevus, nevus lipomatosis and appeandegeal tumor. There was no evidence of hypopigmented macule on wood's lamp examination or skin lesions suggestive of tuberous sclerosis. There was no significant past medical or surgical history. Baseline laboratory investigations including urinalysis were within normal limits. A skin biopsy obtained from the lesion showed focal acanthotic epidermis and significant increased density of collagen bundles in the deep reticular dermis. [Figure 2] Masson's trichrome stain confirmed the presence of dense collagen bundles with decreased elastic fibers. [Figure 3] Abdominal ultrasound did not reveal any renal masses. Chest roentgenogram did not show any abnormality. Radiography of the pelvis and long bones were normal with no evidence of circumscribed areas of increased bone density suggestive of osteopoikilosis. Thus, a diagnosis of sporadic type of isolated collagenoma of the scalp was made.

Figure 1.

A single pedunculated tumor like mass on vertex of scalp

Figure 2.

H and E stained section from pedunculated mass showing acanthotic epidermis and dense collagen bundles in the deeper dermis arranged in a haphazard manner. (×40)

Figure 3.

Masson's trichrome stained section showing green colored staining collagen bundles suggesting excessive collagen. (×40)

Collagenoma (collagen nevus) has been classified into four distinct groups: (i) familial cutaneous collagenoma (FCC); (ii) the Shagreen patch of tuberous sclerosis; (iii) eruptive collagenoma; and (iv) isolated collagenoma.[6] Depending upon the classification of the genetic inheritance pattern, collagenomas are classified as either inherited or sporadic.[7,8] Inherited group includes dermatofibrosis lenticularis disseminata in the Buschke-Ollendorf syndrome, familial cutaneous collagenoma (FCC), and shagreen patches seen in tuberous sclerosis-all are autosomal dominant in inheritance. The acquired group includes eruptive collagenomas and isolated collagenomas. Eruptive collagenomas is characterized by multiple asymptomatic skin colored papules and nodules occurring symmetrically on trunk and upper limbs. FCC also in combination with multiple collagenomas has in addition autosomal inheritance pattern and cardiac disorders like cardiomyopathy and conduction abnormalities.[9,10] Shagreen patches (plaques of collagenoma) are present in tuberous sclerosis with the classic skin findings of facial angiofibromas, periungual fibromas (koenen's tumor), gingival fibromas, fibrous plaque of forehead and ash-leaf macules.

Isolated collagenomas are sporadic and are localized to a single body region as in our case. Cerebriform plantar nevi are considered to be a pathognomic cutaneous marker of Proteus syndrome (a type of epidermal nevus syndrome).[11] However, many authors have reported the occurrence of plantar collagenoma without any co-existent features of Proteus syndrome. A collagenoma on the scalp can give the clinical morphology of cutis verticisgyrata and deserves special mention.[8] Collagenomas have also been reported in association with pseudohypoparathyroidism,[12] Down syndrome[13] and hypogonadism.[14] The pathogenesis of collagenomas is not clear. In a proven case of collagenoma or connective tissue nevi, a further work-up is necessary to rule out any underlying systemic disorder. Table 1 gives the diagnostic evaluation to be done in cases suspected of collagenoma.

Table 1.

Diagnostic work up to be done in case of collagenoma

Histopathology of collagenoma shows increased amount of collagen fibers, with either normal or decreased elastic tissue. Management of extensive collagenoma especially over the plantar surface is difficult and is primarily a surgeon's domain. In our case we could excise the entire mass due to small size of the lesion.