• Skin-colored to pink, soft papulonodule, often on the trunk (see Fig. 50.2).

• Compressible (the tumor often herniates inward upon palpation – this is referred to as the ‘button-hole’ sign); it is sometimes pedunculated.

• Usually solitary in most individuals.

• When multiple, need to distinguish linear form (segmental; mosaic) from a generalized distribution pattern (neurofibromatosis type I) (see Chapter 50).

• Histopathology: wavy, delicate spindle cells with tapered nuclei in a pink stroma.

• Plexiform type has been likened to a ‘bag of worms’ (Fig. 95.1); it is generally on the trunk and proximal extremities, highly associated with neurofibromatosis type I, and prone to malignant degeneration (2–13%).

• Solitary, pink-yellow, soft, smooth papulonodule; generally seen in adults.

• Often on the extremities or head (Fig. 95.2).

• Asymptomatic (rarely painful).

• Histopathology: encapsulated tumor with foci of wavy, spindled nuclei in palisades and foci of myxoid change.

• Often in adults; skin-colored to brown-red, firm papulonodule; sometimes ulcerated or verrucous.

• 30% on the tongue.

• Multiple tumors in 10% of patients.

• Histopathology: polygonal cells with oval nuclei and characteristic granular cytoplasm.

• Skin-colored papulonodule(s) at a site of prior trauma.

• Often painful or ‘sensitive’ (Fig. 95.3).

• Histopathology: haphazardly distributed fascicles of spindle cells with tapered nuclei.

• In older adults; solitary, rapidly growing, pink to red to violaceous nodule (Fig. 95.4).

• Commonly on the head and neck.

• Aggressive behavior: distant metastases in 40%; 70% survival at 5 years if primary lesion is <2 cm in diameter; 18% survival at 5 years if distant metastatic disease.

• Histopathology: islands or trabeculae of blue cells that on high-power magnification have chromatin that appears speckled like ‘salt and pepper’; characteristically cytokeratin 20 (CK20)-positive and thyroid transcription factor-1 (TTF1)-negative.

• Rx: optimally includes wide excision, accompanied by sentinel lymph node biopsy (SLNB); adjuvant radiation treatment recommended for most patients (exceptions: primary ≤1 cm, SLNB negative, no immunosuppression).

• Common; skin-colored to pink or occasionally hyperpigmented, pedunculated papule.

• Sites of predilection: neck, axilla, groin (Fig. 95.5).

• Can become irritated or infarcted.

• Solitary, skin-colored to pink, shiny papule; commonly on the nose (Fig. 95.6).

• When multiple, need to consider genodermatoses (e.g. tuberous sclerosis, multiple endocrine neoplasia type I).

• Histopathology: stellate spindle cells in a hyalinized stroma with dilated vessels.

• DDx: basal cell carcinoma, intradermal melanocytic nevus, adnexal tumors.

• Multiple, small, white to light pink papules along the corona of the glans penis, often with a multilayered distribution (Fig. 95.7).

• Rx: reassurance.

• 6- to 10-mm pink (especially in fair-skinned individuals), tan, or brown papule (Fig. 95.8); firm; dimples inward with lateral pressure.

• Often on the lower extremities; women > men.

• Common; multiple lesions can be seen in normal individuals but also are associated with lupus erythematosus and immunosuppresion (e.g. HIV infection).

• Histopathology: epidermal hyperplasia (sometimes with basaloid induction that resembles basal cell carcinoma) above a spindle cell proliferation that entraps collagen.

• Dermoscopic features are shown in Fig. 1.13.

• 4- to 10-mm solitary, skin-colored to pink, cone-shaped, keratotic papule with a collarette of elevated skin (Fig. 95.9).

• Located on the fingers and sometimes the palms.

• 2- to 9-mm dome-shaped, pearly papule or nodule in adults.

• Slight predilection for the head and neck.

• Can be seen in patients with Cowden disease.

• Firm nodule (1–2 cm), generally on the fingers or toes (Fig. 95.10).

• 30% of tumors recur locally.

• Benign, reactive process in young adults.

• Rapidly growing subcutaneous nodule (1–5 cm in diameter).

• Commonly on the distal upper extremity.

• Sometimes associated with trauma.

• Histopathology: subcutaneous nodule of elongated spindle cells in a myxoid matrix.

• Skin-colored to yellow-tan (more yellow when composed predominantly of elastic tissue), firm papulonodules or plaques; solitary or multiple (often grouped) (Fig. 95.11).

• Present at birth or arise during childhood.

• May be associated with genodermatoses (e.g. tuberous sclerosis, Buschke–Ollendorf syndrome, Proteus syndrome).

• Histopathology: increased collagen (sometimes subtle) and/or elastic tissue; diagnosis may require special stains for elastic fibers and collagen.

• Firm, skin-colored to pink papulonodule on the fingers or toes (tends to spare the thumb and great toe) (Fig. 95.12).

• Solitary or multiple; generally present before 1 year of age.

• May recur.

• One or more skin-colored to pink to violet, firm to rubbery dermal/subcutaneous nodules.

• Most commonly on the head and neck or trunk.

• Rare; lesions present at birth or appear during the first 2 years of life.

• Can have cutaneous lesions alone or systemic involvement (bone, gastrointestinal, kidneys, lungs, heart).

• Tumors tend to self-regress.

• Histopathology: biphasic pattern of spindle cells in nodular arrangements with vessels at the periphery.

• Five subtypes, four of which are superficial: (1) palmar (Dupuytren’s contracture); (2) plantar (Ledderhose disease); (3) penile (Peyronie’s); and (4) knuckle pads (Fig. 95.13).

• One deep form: extra-abdominal desmoid tumor.

• Slowly growing nodules or plaques or cord-like tumors.

• Palmar fibromatosis can result in flexion contractures, especially of the 4th and/or 5th finger (see Chapter 81).

• Penile fibromatosis can result in pain and erectile dysfunction.

• Solitary or multiple red-brown papules or nodules, often grouped (Fig. 95.14).

• Sometimes painful.

• Generally on the trunk.

• When multiple, consider association with uterine leiomyomas and papillary renal cell carcinoma (Reed syndrome).

• Histopathology: fascicles of spindle cells with cigar-shaped nuclei that have perinuclear vacuoles.

• Congenital or acquired, skin-colored to hyperpigmented plaque on the trunk > proximal extremities (Fig. 95.15).

• Follicular prominence and hypertrichosis may be present.

• May be confused with a congenital melanocytic nevus.

• Is on a clinicopathologic spectrum with Becker’s nevus.

• Common tumor of mature fat; soft, mobile subcutaneous nodule.

• Generally on the trunk and extremities, but any site possible.

• Occasionally painful.

• Multiple lesions may be associated with a lipomatosis (e.g. familial type; Fig. 95.16) or a genodermatosis (e.g. Gardner syndrome, Proteus syndrome).

• DDx: see Fig. 95.17.

• Soft, mobile, subcutaneous nodule; often on the forearm in young adults.

• Often painful.

• Grouped, soft, yellow to skin-colored papulonodules on the hips and/or upper thighs (Fig. 95.18).

• Develops during infancy to the first two decades of life.