Dermato ibroma Over The Scar – A Rare Entity

Dermato ibroma is a common benign dermal tumour of unknown aetiology. With varied clinical presentation mimicking keloid, desmoid tumour and leiomyoma, the diagnosis of Dermato ibroma sometimes become problematic from the clinician side. Here, we report a case of Dermato ibroma in a not so common sitewhichwas clinically diagnosed to be a keloid. But later, the lesion turned out to be a dermato ibroma on histopathological examination. In our patient, the lesionwas a single smooth circumscribed nodule over the left side of the abdomen. The lesion had a linear scar on either side and on palpation; it was irm in consistency. It was initially diagnosed to be a keloid which even after multiple intra-lesional steroid injections, failed to show any results. This prompted us to search for an alternate diagnosis; hence lesion was excised and analyzed. The Histopathological examination revealed a circumscribed lesion in the dermis, composed of benign spindle-shaped cells arranged in a storiform pattern. These indings, as mentioned above, were consistent with a diagnosis of Dermato ibroma, which is a slow-growing tumour commonly seen in the extremities. The keloid like a presentation of Dermato ibroma, is one another example of how a similar morphological presentation may have twodistinct diagnoses resulting in a delay in providing appropriate treatment.

Dermato ibroma is a common benign dermal tumour of unknown aetiology. With varied clinical presentation mimicking keloid, desmoid tumour and leiomyoma, the diagnosis of Dermato ibroma sometimes become problematic from the clinician side. Here, we report a case of Dermato ibroma in a not so common site which was clinically diagnosed to be a keloid. But later, the lesion turned out to be a dermato ibroma on histopathological examination. In our patient, the lesion was a single smooth circumscribed nodule over the left side of the abdomen. The lesion had a linear scar on either side and on palpation; it was irm in consistency. It was initially diagnosed to be a keloid which even after multiple intra-lesional steroid injections, failed to show any results. This prompted us to search for an alternate diagnosis; hence lesion was excised and analyzed. The Histopathological examination revealed a circumscribed lesion in the dermis, composed of benign spindle-shaped cells arranged in a storiform pattern. These indings, as mentioned above, were consistent with a diagnosis of Dermato ibroma, which is a slow-growing tumour commonly seen in the extremities. The keloid like a presentation of Dermato ibroma, is one another example of how a similar morphological presentation may have two distinct diagnoses resulting in a delay in providing appropriate treatment.

INTRODUCTION
Dermato ibroma also known as ibrous histiocytoma, or sclerosing hemangioma is one of the most common benign mesenchymal neoplasms. This tumour occurs due to the reactive proliferation of ibroblasts (Myers et al., 2020). It is usually seen on the extremities in mid-adults with a slight female predominance (Pusztaszeri et al., 2011). The aetiology of Dermato ibroma is usually unknown but may occur following trauma suggesting a reactive or reparative process. It usually presents as single or multiple papules or a nodule or a plaque with overlying skin colour being red to brown because of higher intraepidermal melanin or tumoral hemosiderin.
The diagnosis of Dermato ibroma is primarily clinical. The 'Dimple sign' characteristic of Dermato ibroma can be elicited by side-to-side compression of the lesion. This produces a characteristic dimple due to the tethering of overlying epidermis to the lesion beneath. This is also called a Fitzpatrick sign and can also be elicited by keeping an ice cube over the lesion (Patel et al., 2011).
Dermatoscopy may be a useful tool in diagnosing Dermato ibroma, where a peripheral pigment network with a central white area is seen (Zaballos et al., 2008).

Case report
A 67 old female with a previous history of abdominal surgery 25 years back presented to our OPD with complaints of skin coloured raised lesion over the abdomen associated with mild itching for the past 18 months. Routine systemic examination was normal. Dermatological examination revealed a single, smooth, well-circumscribed nodule of 1×1 cm with no surface changes present over the left side of the abdomen. There was a linear scar on either side of this lesion. On palpation, it was ixed and irm [Figure 1]. We initially diagnosed it as keloid and treated it with multiple sessions of Intra-lesional corticosteroid injections. But the lesion did not respond to the injections and also developed atrophy of the surrounding skin. Hence other differentials like Dermato ibroma, desmoid tumour, leiomyoma were considered, excision biopsy was done and sent for histopathological examination.

DISCUSSION
Cutaneous Dermato ibroma is a benign slowgrowing soft tissue tumour, often presenting as single or multiple irm yellow-brown or red-brown nodules. It is commonly seen on the extremities, rarely on palms, soles, ingers, genitals, head and neck (Bandyopadhyay et al., 2016;Parish et al., 2012). Although asymptomatic, itching and tenderness may be present (Zelger et al., 2004). It usually presents as a solitary lesion, and rarely multiple lesions are found which is commonly associated with autoimmunity or altered immunity. 'Dimple sign' can be elicited by lateral compression of the lesion. This is due to the tethering of overlying epidermis to the lesion beneath. This is also called a Fitzpatrick sign and also elicited by keeping an ice cube over the lesion (Patel et al., 2011).
In our case, the lesion was a solitary nodule of 18-month duration, irm in consistency without an increase in size. Dimple sign was negative. It was non-responsive to multiple intralesional steroid injections. Failure to respond to the treatment prompted us to do an excision biopsy which revealed Dermato ibroma with classical indings.
Histologically, in Dermato ibroma, the epidermis will be hyperplastic with increased pigmentation of the basal layer (known as 'Dirty ingernail sign' ) (Parish et al., 2012). The tumour present in the mid dermis would have whorled fascicles of spin-dle cell proliferation and excess collagen. Various histopathological variants have been described. Dermoscopy may also aid in our diagnosis where peripheral pigment network with a central white area, though we haven't done that in our case.
Treatment is not necessary. Reassurance is given regarding the benign nature of the tumour. Complete surgical excision is ideal, though intralesional steroids, super icial shaving or cryotherapy, CO2 laser, pulsed dye laser have been tried with varying results (Shankar et al., 2007;Alonso-Castro et al., 2012).

CONCLUSIONS
Dermato ibroma is a common tumour with varied presentations. Keloid like presentation is one of the rare forms which is usually associated with trauma and often misdiagnosed to be a Keloid as in our case. In such a case, giving due importance to all the differentials and in-depth clinical examination with the use of aids like biopsy or dermoscopy or both may narrow down the chances of making an error.

ACKNOWLEDGEMENT
I would like to thank members of the Department of clinical pathology & Department of DVL for their help & support.