INTRODUCTION

Pigmented dermatofibrosarcoma protuberans or previously known as Pigmented storiform neurofibroma is a rare variant of DFSP ,described by BEDNAR in 19571.The histological picture shows melanin laden dendritic cells with spindle shaped cells in storiform pattern.The tumour mostly occurs on trunk,upper and lower extremities,few in head and neck region2..It is a slow growing,locally invasive-painless cutaneous multilobulated lesion, burn or surgical scar3 at the initial stage often the cause.

It has been shown that Giant cell Fibroblastoma has a close histogenic relationship to Dermatofibrosarcoma protuberans4 and it has been reported that Giant cell fibroblastoma can transform into DFSP5-7.We present here a case of massive Bednar tumour of neck region presenting five years after initial excision.

CASE REPORT

A 68 year old female was admitted with a huge painless nodular tumour

over the neck region. She gives history of  insect bite  at the same  spot  eight years

back following which a tumour developed over next one year slowly growing upto

four cm in diameter. The lesion was excised under local anaesthesia and histological

diagnosis  revealed  Dermatofibroma. She had another recurrence of the tumour two

year following the first excision which she neglected and the tumour gradually

progressed to a very large size.

              The patient denied fever , chills, bony pain  or any other constitutional

symptoms.   On physical examination ,patient  was not cachectic with no palpable

lymphadenopathy.Respiratory, CVS and GI exam was within normal limits.

Skin examination revealed   40 x 34 cm exophytic  mass over neck region with

multiple soft protuberances  of varying size none exceeding 8 cm,soft in consistency

with thin skin cover over  certain areas with ulceration. The nodules appeared fixed

to the overlying skin but were mobile over the deep tissue.There  was no other

positive finding on  complete head and neck examination and there was no other

swelling  elsewhere in the body.

              Lab. Findings were within the normal limits.Chest X-ray  was WNL.

Computed tomography ( CT ) revealed no invasion of  the mass into deeper

structures .

             A wide and deep excision with 3 cm margins of normal tissue  all around

the lesion was performed.  Grossly,the resected specimen measured 40 X 36X26 cm diameter  with multiple discrete nodular mass,the greatest being 8 cm in diameter. The nodules were well circumscribed,had a firm consistency and showed a whorled pattern on cut section.

              On histologic examination ,they were found to be composed of a uniform

population of fibroblast like cels,arranged in a storiform pattern . The cells had  hyperchromatic oval to spindle shaped nuclei with low mitotic activity.The striking  feature was presence of bipolar and multipolar dendritic cells with tentacle like processes emanating from nucleus .

                Immunohistochemical study showed positive reaction to CD 34 and

VIMENTIN and negative for protein S-100  but melanin containing cells showed

positive for protein S-100.

                The resected specimen showed tumour free margins. Soft tissue

reconstruction was done at the resected site of tumour.

Figure 1

Macroscopic view of tumour located on anterior part of chest wall.

Figure 2

Postoperative view of the resected Specimen ( 40 x 36 x 26 cm )

Figure 3

Neoplasia occupying the dermis and compose of fusiform cells and cells containing melanin

Figure 4

Melanin pigment seen in cells of dermis and Subcutaneous layer

Figure 5

Immunohistochemistry—Positivity for antibody against CD 34,which confirmed the diagnosis

Retrograde histological re-examination of the specimen obtained from the second excision of the recurrent tumour showed high expression of CD34 and revealed present tumour was actually a recurrence of this tumour.

           The wound healed without any complication and the post operative course was uneventful,with no paraesthesia or skin sloughing at the reconstruction site.

DISCUSSION

              The case presented here was DFSP ,which was initially mistaken to be

dermatofibroma.Dermatofibromas composed predominantly of fibroblasts extending

into the subcutaneous tissue are difficult to distinguish from dermatofibrosarcoma

protuberans8  though the patterns are different.

               Bednar tumour account for less than 5 % of all  DFSP9 and more common

in  Black  male population .Different theories have been given regarding origin of 

Pigment laden cells .Dual cell origin suggests  CD 34  positive spindle  cells of 

Mesenchymal and pigmented cells of neuroectodermal origin10.

              In the case reported here correct clinical diagnosis was not reached initially

but only later  on recurrence after subjecting to histopathological and

immunohistochemical studies.Condensation of connective tissue at the periphery

may give a false appearance of encapsulation but tumour may extend well beyond

margins11. We need to be aware of  this condition12 and confirm  histological

diagnosis before excision.

              Recurrence are due to inadequate excision with  tumour extending to deep

resection margin. With recurrence the lesion becomes less  well differentiated13 and

chances of  metastasis increases.Though rare,dissemination  occurs by hemategenous

route  and rarely lymphatically . The principal site being lungs though  

bones,liver,pancreas,stomach,intestine,thyroid and brain may be involved

               Surgery with a safety margin of  3 cm including  the underlying fascia

serves good with Computerized tomogram helpful in deciding the line of incision to

prevent recurrence or metastasis.Mohs micrographic surgery14 has maximum

oncologic effectiveness and is the accepted treatment of choice.

              Chemotherapy is not used in treatment while radiotherapy can be used as

adjunct to surgery  in cases with positive resection  margins.Molecular targeted

therapy and Imatinib may provide alternative treatment to unresectable tumours or

adjunctive treatment in addition to surgery.

                   In short ,Bednar tumour is a rare tumour.Painless ,cutaneous and

multilobulated lesion should arouse suspicion of this tumour  and core or incision

biopsy should aim at pre-operative histologic diagnosis.Adequate excision will avoid

recurrence and excellent prognosis.