Dear Editor,
A 19-year-old female patient presented with a lump over her left arm for 3 years. The lump was mobile, firm and non-tender on palpation measuring 3.5 cm in the largest dimension. The lump appeared to be in the subcutaneous plane. The lump was shelled out during the excision biopsy. On gross, the lump was a 3.5 × 2.5 × 1.5 cm globular mass, having a white, firm and homogenous cut surface (Fig. 1). Microscopy showed a well circumscribed moderately cellular lesion composed of plump spindle cells dispersed in loose short intersecting fascicles with entrapped collagen bundles and interspersed thin delicate capillaries (Fig. 2). Many dispersed large cells with foamy cytoplasm were seen. The tumour cells showed moderate to marked anisonucleosis with many ‘'monster forms' having bizarre nuclear forms and coarse chromatin (Fig. 3). Mitotic figures and necrosis were absent. Immunohistochemistry showed the tumour cells to be positive for Vimentin (Pathnsitu, Clone V9, diffuse and cytoplasmic) and CD34 (Pathnsitu, Clone EP88, patchy and membranous) (Fig. 4A). The foamy cells are positive for CD68 (Pathnsitu, Clone KP-1, patchy, granular and cytoplasmic) (Fig. 4B) and S100p (Pathnsitu, Clone EP-32, cytoplasmic). Ki67 (Pathnsitu, Clone MIB-1) proliferative index was less than 1%. A diagnosis of dermatofibroma with monster cells was offered.
Fig. 1.
Homogenous whitish cut surface of the gross specimen.
Fig. 2.
Haematoxylin and Eosin (40x magnification). Tumour is composed of an admixture of spindle and scattered foamy cells in a collagenous background.
Fig. 3.
(A–D) Haematoxylin and Eosin (400x magnification). Many tumour cells have bizarre ‘monster’-shaped nuclei.
Fig. 4.
A) Immunohistochemistry with CD34 shows interrupted membranous staining in tumour cells with endothelial cells being internal control. (B) Immunohistochemistry with CD68 shows patchy granular cytoplasmic staining in the foamy cells.
Dermatofibroma is a well-demarcated mesenchymal tumour made up of a combination of histiocytes and fibroblasts arranged in fascicles or sheets having an admixture of foamy and/or hemosiderin-laden macrophages and variable number of inflammatory cells.1 Presence of bizarre pleomorphic cells is a rare occurrence and is considered as a degenerative change, in the absence of mitosis.2 This entity was initially described by Ackerman in 1987.3 A differential diagnosis includes nodular fasciitis, leiomyoma, dermatofibrosarcoma protuberans and pleomorphic sarcoma.4 The differentiators include the tumour circumscription, absence of mitosis and immunophenotype of patchy CD34, and strong factor XIIIa with scattered CD68-positive histiocytes.1,4,5 Treatment strategy involves excision of the tumour mass with a margin to prevent local recurrence.4 Knowledge of this rare variant is vital to differentiate it from more sinister tumours, and mere presence of grotesque nuclei should not lure the pathologist into reporting a sarcoma. Informed consent of the patient was obtained for submission of figures and data for publication.
Patients/ Guardians/ Participants consent
Patients informed consent was obtained.
Ethical clearance
Not Applicable.
Source of support
Nil.
Disclosure of competing interest
The authors have none to declare.
Acknowledgements
The paper was presented as a poster presentation at APCON 2022.
References
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