A rare cause of scarring alopecia

Paediatric dermatology
Adnexal diseases
Scalp pathology

Dr. Emmanuelle Bourrat

Saint-Louis Hospital

The clinical case
Now it's your turn!
Co-prescription and advice

Clinical case presentation

An 11-year-old girl presented with a patch of paramedian alopecia on the vertex that had been slowly progressing for several months. She had no previous history of inflammatory dermatosis of the scalp nor any history of trauma to this area. The lesion, about 2 cm in diameter, was well limited, totally hairless, with a non-inflammatory but slightly purplish scalp, very infiltrated and slightly tender to palpation. There was no satellite adenopathy and the rest of the examination was normal; in the absence of a clinical diagnostic hypothesis, a biopsy was performed.

Your turn

What is your diagnosis?

Select 1 answer(s) from the following choices:

Alopecia areata

Sebaceous hamartoma

Dermatofibrosarcoma of Darier-Ferrand

Nodular fasciitis

Wrong answer!

Good answer!

Selected diagnosis

The histological appearance is that of nodular fasciitis, a benign tumor (probably reactive proliferation) of spindle-shaped myofibroblasts affecting the subcutaneous tissues (fascia, muscle, bone in exceptional cases) of children and infants. It is usually localized to the head, neck or trunk, limited in size, initially growing rapidly and sometimes painful to palpation.

Clinically, its very firm consistency and low mobility in relation to the deep planes suggest a fibrous tumor; its painful nature is a good indication of nodular fasciitis, but a biopsy is essential to rule out another fibromatosis or Darier-Ferrand sarcoma.

Histologically, diagnosis can also be difficult with these entities, and a cytogenetic study using FISH may be useful to demonstrate a translocation involving the MYH9 and USP6 genes. Treatment is based on simple excision, although postoperative recurrence and spontaneous regression are possible.

Explanation of wrong answers

Alopecia is ruled out by the infiltrative nature of the alopecic patch.
The sebaceous hamartoma is hairless and well-limited but congenital, papular rather than infiltrated, yellow or pinkish rather than purplish. It is neither painful nor progressive on the surface.
Darier-Ferrand dermatofibrosarcoma is the differential diagnosis for any localized “fibromatous” skin lesion (slowly progressive infiltrated red or brown plaque), whatever its topography. Pediatric forms, including congenital forms, have been described. Diagnosis requires dermatopathological and genetic expertise (translocation t(17;22)(q22;q13) is virtually constant).

Treatment

The first-line treatment for nodular fasciitis is simple excision, although spontaneous regression has been described.

Message from the expert

“Fibromatoses” and myofibroblastic proliferations in children constitute a vast heterogeneous group of clinically non-specific lesions whose diagnosis and prognosis require deep surgical biopsy and dermatopathological and sometimes molecular expertise.

References:

^{Patel D, Samson TD, Cochran EL, Zaenglein AL.Nodular fasciitis on the cheek of a child.}

^{Pediatr Dermatol. 2021;38(2):508-509}