Dermatology Online Journal
Hypocellular medallion-like dermal dendrocyte hamartoma (plaque-like CD34-positive dermal fibroma)
- Author(s): Bagazgoitia, Lorea
- Moreno, Carmen
- et al.
Hypocellular medallion-like dermal dendrocyte hamartoma (plaque-like CD34-positive dermal fibroma)1. Department of Dermatology
Lorea Bagazgoitia PhD1, Carmen Moreno2
Dermatology Online Journal 17 (9): 8
2. Department of Pathology
Hospital Ramón y Cajal, Madrid, Spain
Universidad de Alcalá de Henares, Spain
Medallion-like dermal dendrocyte hamartoma (MLDDH) is a recently described congenital dermal neoplasm. Only 11 cases have been reported in the English literature and therefore its clinical and pathological manifestations are not completely defined. We report the case of a 20-year-old male presenting with a round, erythematous, atrophic plaque on the midline of the anterior aspect of the neck. The lesion was asymptomatic and was stable since birth. A skin biopsy was performed. Histological examination showed a band like hypocellular fibrotic area in the superficial reticular dermis, which did not spread to subcutaneous tissue. The cells were CD34-positive and S100 and CD56-negative. Elastic fibers were present. Altogether the morphological and immunostaining features were neither suggestive of dermatofibrosarcoma protuberans nor neurofibroma. Thus, the pathological findings were consistent with MLDDH. Clinical differential diagnosis includes anetoderma, aplasia cutis, or atrophic DFSP. Histological differential was made with atrophic scar and striae distensae. Although the histological findings were not identical to those described recently as characteristic, the clinical features were suggestive enough to make the diagnosis of MLDDH. Therefore in our experience, the MLDDH spectrum might include lesions with variable cellular density, which can show similar clinical manifestations.
Medallion-like dermal dendrocyte hamartoma (MLDDH) is a recently described dermal neoplasm. We present a clinically unusual MLDDH, showing remarkably poor cellularity, which does not completely fit the diagnostic criteria established by Kutzner et al .
A 20-year-old male had a congenital, asymptomatic lesion which was an atrophic, erythematous, well-defined plaque on the frontal aspect of his neck. It had enlarged over the years with the normal growth of the patient. Physical examination and the personal and family history were unremarkable.
Histopathological examination showed a band-like CD34-positive hypocellular fibrotic area in the superficial reticular dermis, which did not spread to the deep reticular dermis and subcutaneous tissue. Orcein stain showed normal elastic fibers. S-100 and CD56 were negative.
MLDDH was first described by Rodriguez-Jurado et al. in 2004. Seven additional cases have been reported in the English literature.
Congenital atrophic dermatofibrosarcoma protuberans (DFSP) is considered an important condition in the differential diagnosis for MLDDH . CD34 immunostains, have traditionally been useful to distinguish DFSP from other fibrohistiocytic tumors. This immunomarker does not seem useful in this case because MLDDH has been shown to be positive for CD34 in all the cases reported. Therefore, the need of a complete histological and immunohistochemical examination and a molecular analysis to detect the COL1A1-PDGFB fusion gene have been emphasized . Moreover, although atrophic dermatofibroma can also show CD34-positive cells, these are usually focal and not diffuse as in our case.
Kutzner et al. defined several specific histological features of MLDDH. Dilated venules and a storiform pattern of fibroblasts surrounding the adnexae and vessels were observed. A 2-layer pattern was also described in the dermal infiltrate: a vertical orientation on the upper layers and a horizontal one in the lower layers. In their series, 4 non-congenital cases were included, which presented in patients older than 52 years of age and were located on the limbs. However, the clinical aspect of these lesions did not seem so characteristic because they were initially diagnosed as lichen planus, dermatofibroma, or nevus. There might be a wide clinical variability histologically compatible with MLDDH.
Clinically our case is concordant with the description made by Rodríguez-Jurado et al . Anetoderma and aplasia cutis were excluded through the histological examination, as was atrophic DFSP. There was a remarkably low cellular density without storiform pattern that was embedded in a fibrotic background. It was a superficial thin band-like pattern without involvement of deep reticular dermis or the dermohypodermal junction, as would be expected in DFSP . Clinically the lesion had remained stable for 20 years. Therefore molecular analysis to detect the COL1A1/PDGFB fusion gene was not performed.
Although our case does not show the histological criteria proposed recently, in our experience, it represents a type of MLDDH, showing lower cellular density than previously reported cases. The fact that our case shows greater similarity with the histology described for congenital lesions , and that most cases presented by Kutznet et al. were acquired, might mean that there are not only clinical, but also histological differences between the acquired and the congenital types. Therefore this case may represent a hypocellular variant of the not yet completely characterized congenital type of MLDDH.
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