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CORRESPONDENCE
Year : 2022 | Volume
: 40
| Issue : 1 | Page : 60-61
Fibrous hamartoma of infancy with smooth muscle differentiation: A case report
Yu-Ju Chou1, Han-Nan Liu2, Chih-Chiang Chen3
1 Department of Dermatology, Taipei Veterans General Hospital; School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
2 Department of Dermatology, Taipei Medical University-Shuang Ho Hospital, Ministry of Health and Welfare, Taipei, Taiwan
3 Department of Dermatology, Taipei Veterans General Hospital; School of Medicine; Department of Dermatology, National Yang Ming Chiao Tung University; Institute of Clinical Medicine, National Yang-Ming Chiao Tung University, Taipei, Taiwan
Correspondence Address:
Dr. Chih-Chiang Chen
Department of Dermatology, Taipei Veterans General Hospital, No. 201, Sec. 2, Shipai Rd, Beitou District, Taipei City
Taiwan
Source of Support: None, Conflict of Interest: None
DOI: 10.4103/ds.ds_10_22
Dear Editor,
A 5-year-old male patient was brought to our outpatient clinic with the chief complaint of an asymptomatic tumor on his back since birth. According to his family, the tumor was flat at birth, and a previous ultrasound had reported a fusiform hypoechoic lesion measured 1.4 cm at the dermis of the right middle back, showing increased vascularity. The lesion is suspicious of hemangioma. However, the tumor had become larger and begun protruding in the months before this visit. Physical examination revealed a 2.5 cm × 2.5 cm, skin-colored, rubbery-to-firm nodule on his back. After obtaining consent from the patient's family, an excisional biopsy was performed. We had followed up the patient for 5 months after surgical intervention, and no recurrence was noted.
The histology report revealed a well-defined tumor from the upper dermis to the upper subcutis [Figure 1]a. The tumor was composed of haphazardly arranged spindle cells, intersecting fascicles of fibroblastic or myofibroblastic tissue [Figure 1]b, mature adipose tissue [Figure 1]c, and focal myxoid stroma with spindle to stellate mesenchymal cells [Figure 1]d. In addition, interlacing bundles of spindle cells with cigar-shaped nuclei and eosinophilic cytoplasm are noted [Figure 1]e and [Figure 1]f. Immunohistochemical staining of the tumor cells demonstrated diffuse positivity for CD34 [Figure 2]a, focal positivity for smooth muscle actin, mainly in the fibroblastic area [Figure 2]b, and focal positivity for desmin, mainly in the fibroblastic area [Figure 2]c and [Figure 2]d. Although the histomorphology in this case was overall consistent with the diagnosis of fibrous hamartoma of infancy (FHI), our case showed substantial muscular differentiation which had not been documented previously.
Figure 1: The histology report revealed a well-defined tumor from the upper dermis to the upper subcutis (a). The tumor was composed of haphazardly arranged spindle cells, intersecting fascicles of fibroblastic or myofibroblastic tissue (b), mature adipose tissue (c), and focal myxoid stroma with spindle to stellate mesenchymal cells (d). In addition, interlacing bundles of spindle cells with cigar-shaped nuclei and eosinophilic cytoplasm are noted (e and f).
Figure 2: Immunohistochemical staining of the tumor cells demonstrated diffuse positivity for CD34 (a), focal positivity for smooth muscle actin, mainly in the fibroblastic area (b), and focal positivity for desmin, mainly in the fibroblastic area (c and d).FHI is a rare soft-tissue tumor that mainly affects infants and young children and is predominant in males (male:female ratio = 2.7).[1] Approximately 4% of the cases are congenital. The mean tumor size is 3.0 cm, and commonly affected sites include the axilla, back, upper arms, scrotum, and chest wall. While most cases are asymptomatic, hypertrichosis and hyperhidrosis have been reported in some cases.[2] Computed tomography or magnetic resonance imaging of FHI displays strands of adipose or fibrous intensities traversing the lesions, with an occasional characteristic parallel or whirling appearance.[3] Histopathologically, FHI is a poorly delineated subcutaneous lesion with a characteristic triphasic morphology, comprising haphazardly arranged fascicles of fibroblastic or myofibroblastic cells, mature adipose tissue, and myxoid nodules of primitive-appearing spindle to stellate mesenchymal cells. The relative proportion of the three components mentioned above varies, with approximately one-third of cases showing an even distribution.[1] The differential diagnosis includes dermatomyofibroma, fibroblastic connective tissue nevus, lipofibromatosis, and congenital smooth muscle hamartoma. Immunohistochemical stainings of FHI typically show smooth muscle actin positivity in the fibroblastic area, S100 positivity in mature adipose tissue, and CD34 positivity in the fibroblastic area and primitive mesenchymal component.[4] Previous studies have reported mostly negative findings of desmin,[1],[4] but few cases also report focal reactivity for desmin.[4],[5] Groisman and Lichtig suggests the origin of myofibroblasts in FHI are either modified pre-existing fibroblasts or modified immature mesenchymal cells which differentiate between fibroblasts and smooth muscle cells. The latter may explain the positive results of desmin.[5] In addition, they propose no smooth muscle cell is found in FHI. However, our case shows that reactivity for desmin is partially contributed to the smooth muscle components. To the best of our knowledge, although the histopathological and immunohistochemical results of our case indicate FHI, the tumor shows smooth muscle differentiation that has not been reported previously. In addition, compared to previous cases, the lesion in our case was relatively well circumscribed and located superficially.
Most patients with FHI have undergone complete excision, whereas some have received partial excision to preserve vital structures. Dickey and Sotelo-Avila recorded 18 recurrences among 197 cases, with an average recurrence duration of 5.4 months after surgery.[6]
In summary, we present a case report on FHI with smooth muscle differentiation. Because FHI is a rare condition, further histopathological studies are needed for the better understanding of this soft-tissue tumor.
Declaration of patient consent
The authors certify that they have obtained appropriate patient's guardian consent form. In the form, the guardian has given the consent for the child's images and other clinical information to be reported in the journal. The guardian understands that the child's name and initial will not be published and due efforts will be made to conceal the identity, but anonymity cannot be guaranteed.
Acknowledgments
We gratefully appreciate Dr. Yu-Hung Wu and Dr. Chen-Hsiang Hsiao for their pathological consultation.
Financial support and sponsorship
This study was funded by Yung Shin Pharm. Ind. Co., Ltd., the Ministry of Science and Technology, R.O.C. (MOST 109-2314-B-010-014-MY3), and Taipei Veterans General Hospital, Taiwan (VN109-04).
Conflicts of interest
Dr. Chih-Chiang Chen, an editorial board member at Dermatologica Sinica, had no role in the peer review process or the decision to publish this article. The other authors declared no conflicts of interest in writing this paper.
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