Bone- and cartilage-forming tumors and tumors of joints

Primary osteoma cutis represents about 15% to 30% and secondary forms represent about 70% to 85% of cases

Plaquelike osteoma cutis

• Congenital or within the first year of life

• Acquired lesions presenting in adults appear to be more common in males, with predilection for the head, and especially the face

Multiple miliary osteomas

• Middle-aged Caucasian women

• History of severe acne in about 55%, also reported after bisphosphonate (alendronate) therapy for osteoporosis, artificial tanning, severe blistering secondary to sunburn, and exogenous ochronosis

Other types of secondary osteoma cutis

• No sex, age, or site predilection

Asymptomatic, skin-colored papule(s), plaque(s), or nodule(s) of hard consistency

Primary osteoma cutis

• Solitary, plaquelike, multiple, or widespread (disseminated)

• Can be the presenting sign of an underlying syndrome, especially in infancy

Plaquelike osteoma cutis

• Reddish or skin-colored plaque of hard consistency

• Size usually less than 15 cm

• Predilection for scalp, face, and limbs, but any site can be affected

• Criteria for the diagnosis include

  • Presence at birth or during first year of life

  • At least one bony plate with/without other cutaneous osteomas

  • No evidence of abnormalities in calcium or phosphorous metabolism

  • No history of infection or trauma or any other predisposing event(s)

Secondary osteoma cutis

• Solitary or multiple

Multiple miliary osteomas

• Numerous skin papules

• Progressive increase in numbers and peripheral spread frequently reported

• Bluish hue of the papules, especially when history of minocycline treatment

• Size from 1 to 3 mm

• Scalp and face, followed by trunk, breast, extremities, and buttocks

Multiple lesions and plaquelike growth can be cosmetically disturbing

Topical tretinoin therapy, surgical excision, needle mini-incision followed by osteoma extraction, laser treatment, dermabrasion

Lamellar mineralized bone, typically arranged concentrically in the dermis, subcutis, or both

Osteocytes and osteoblasts embedded within the bone, most frequently at the periphery, whereas osteoclasts are much more infrequent

Medullary spaces containing adipose tissue and variably abundant bone marrow (usually absent)

Rim of fibroblasts frequently surrounds lamellar bone

Transepidermal elimination of bony spicules occasionally present

GNAS gene mutations encoding G-protein alpha-stimulatory subunit in patients with progressive osseous heteroplasia, Albright hereditary osteodystrophy, platelike osteoma cutis, and pseudohypoparathyroidism type 1a

ACVR1 gene mutations encoding receptors for bone morphogenetic proteins in patients with fibrodysplasia ossificans progressiva

Osteochondroma (benign cartilaginous exostosis)

Significant higher incidence in patients of African descent

No sex predominance

Usually starts in the first and second decade of life

Local, painless swelling progressing to firm mass with reduced joint mobility

Ulceration of the overlying skin with secondary inflection not uncommon

Pain inconsistent, usually associated with compression of the local nerve

Predilection for large joints of the hips, shoulders, and elbows, less often hand and wrist

Usually lobular/multilobular, densely calcified mass in the periarticular soft tissue, most commonly localized at the extensor surface of joints along the bursa

Ocular involvement ranging from angioid streaks to corneal calcification deposits occasionally present

Early surgical excision to prevent joint limitation(s), but associated with high recurrence rate

Surgical excision combined with phosphate deprivation (aluminum hydroxide) in conjunction with acetazolamide has proven the most effective

Histological features depend on the stage of evolution

Early lesions

• Multiple pseudocystic spaces filled with eosinophilic debris undergoing calcification

• Pseudocystic spaces lined by epithelioid macrophages and multinucleated giant cells

Advanced lesions

• Densely calcified material

• Hyalinized connective tissue

Not contributory

Calcinosis of chronic renal failure

Calcinosis universalis (typically involving multiple tissue planes like subcutis, muscles, and fascia, frequently associated with connective tissue diseases)

Calcinosis circumscripta (dermal and/or subcutaneous nodules at diverse sites, often in the context of connective tissue diseases)

Calcific tendonitis

Male predominance

Most common in patients between 30 and 60 years of age

Familial and congenital occurrence exceptional

Slowly growing, well-demarcated, asymptomatic mass or nodule

Solitary lesions by far predominate

Occasionally painful

Lesions localized at the ungual/periungual site (e.g., nail matrix, nail bed) frequently associated with nail dystrophy/deformity

Less than 2 cm in the majority of cases

Closely associated with the tendon, tendon sheath, joint capsule, or periosteum

Strong predilection for extremities (over 90%), in particular, hands and feet, with fingers being the most common single site

Exceptional sites include dura, spinal canal, oral cavity, pharynx, larynx, skin, fallopian tube, and parotid gland

Uniformly benign clinical course; no malignant transformation has been reported

Complete excision curative

Recurrences after marginal/incomplete excision in roughly 10% to 15%

Well-circumscribed, lobular/multilobular proliferation in the dermis and/or subcutis

Mature adult-type hyaline cartilage is the principal, often exclusive, component of the lesion

• Mature chondrocytes, typically arranged in cords/rows

• Absent or mild nuclear pleomorphism

• Absent or a few normal mitoses

• Occasional binucleated cells (binucleated lacunae)

• Abundant chondroid matrix

Chondroblastic variant

• Hypercellular proliferation in comparison with adult-type cartilage

• Immature cells, resembling chondroblasts

• Plump, rounded or spindled nuclei

• Prominent eosinophilic cytoplasm

• Considerable variation in size and shape (e.g., nuclear and cytological atypia)

• Normal mitoses can be present, but atypical mitoses absent

• The presence of immature cells is not related to biological potential

Richly vascularized stroma

Secondary changes (can be extensive)

• Calcifications, outlining lacunae in a “lacelike” or “chicken-wire” pattern, or more extensive (e.g., “tumoral calcinosis–like”)

• Metaplastic ossification, especially at the periphery of the lobules

• Myxoid change

• Cystic degeneration

• Hemorrhage

• Focal granuloma–like proliferation of histiocytes and osteoclast-like giant cells present in about 10% of the lesions, usually at the periphery of the tumor lobules

S100-protein positive

Markers of epithelial differentiation negative

Cytogenetic analysis performed on limited numbers of soft tissue chondromas detected clonal chromosomal abnormalities in a subset of cases, none of them consistent, including monosomy of chromosome 6, rearrangements of chromosome 11, supernumerary rings derived from chromosome 12, and rearrangements of chromosome 12q13–q15

Activating IDH1 mutations are not seen

Enchondroma

Synovial chondromatosis

Skeletal chondrosarcoma extending into the surrounding soft tissue

Rare

Wide age range with predilection for young adults

Males more commonly affected

Rapidly growing

Small lesion

Nonspecific painful swelling

Fingers more commonly involved than toes

Predilection for proximal phalanx

Lesions not attached to bone

Simple excision

Local recurrences are exceptional