A rare giant extraocular, anterior chest wall sebaceous carcinoma

Highlights • Sebaceous carcinoma is a rare adnexal tumour.• It occurs sporadically or in association with Muir-Torre Syndrome (MTS).• MTS is a rare genetic disorder that predisposes patients to visceral and skin malignancies.• Chest wall is rare site of sebaceous carcinoma.• Surgical excision with wide margins is the standard treatment.


Background
Sebaceous carcinoma is a rare skin cancer derived from the epithelium of the sebaceous gland [2]. It is predominantly found on the periocular region and occurs commonly in Asian women [3]. It is categorized into ocular and extraocular. The common site is ocular, which, accounts for 75 % of cases [3]. Sebaceous carcinomas (SCs) form less than 1 % of all cutaneous malignancies [3]. It may occur sporadically or be associated with Muir-Torre Syndrome (MTS), which is a familial autosomal inherited disorder. Extraocular sebaceous carcinomas are thought to be uncommon and less aggressive than ocular counterparts [4].

Case presentation
The patient is a 45-year-old African male who presented with a two-year history of small lump on the right anterior chest wall. He reported that it was painless, firm and covered by hyper-pigmented skin. He sought for medical assistance after a year of noticing a gradual growth of the lesion. Subsequently, an incisional biopsy was done and histology results confirmed sebaceous adenocarcinoma. The patient absconded and presented a year later with a very large, pedunculated, mushrooming and fungating tumour. Its stalk was on the second intercostal space extending to the parasternal area (Fig. 1 A). The risk factors of this patient were age (45 years) and Human Immunodeficiency Virus; that is to say, he was HIV positive. On local examination, the tumour was found on the right anterior chest wall, with short and broad stalk on the second intercostal space and parasternal area. It had a mushroom configuration, which on long axis was extending from supraster-   nal notch to the lower third of sternal body. Transverse extend of the tumor was from right mid-clavicular line up to left parasternal area. The tumour was multi-lobulated, firm, non-tender, fixed to chest wall and had hyper-vascular, with sloughing areas. It was measuring 180 × 140 × 30 mm. There was no associated regional lymphadenopathy on examination. Examination findings of the other systems were normal.
Postero-anterior (PA) and lateral chest x-rays (CXRs) were done, with a PA showing multi-lobulated soft tissue homogeneous opacity in the upper mediastinum, which extends to the right hemithorax ( Fig. 2A). A lateral view showed anterior chest wall homogeneous opacity extending from thoracic inlet up to the level of sterno-manubrial joint (Fig. 2B).
A non-contrast computed tomography (CT) scan showed anterior chest wall tumour with a calcified capsule without bones involvement (Fig. 3A). A CT-scan with contrast on axial cuts showed a large tumour, with a broad stalk. The tumour was infiltrating the right pectoralis muscle, as evidenced by loss of subcutaneous plane between the tumour and the muscle (Fig. 3B). A type 2-weighted image (T2W) axial magnetic resonance imaging (MRI) view with contrast showed a hyper-intense tumour (Fig. 4A). The broad and short stalk was also demonstrated, invading the right pectoralis muscle. A T2W sagittal view showed that a tumour was extending superiorly up to thoracic inlet and inferiorly up to superior third of sternal body (Fig. 4B).
Total excision of the tumour was undertaken with 1.5−2 cm wide surgical margins, both peripheral and deep. The invaded part of right pectoralis major muscle was also resected en bloc (Fig. 5A, B). A frozen section confirmed negative margins and the defect was dressed with a vacuum assisted closure (VAC) dressing to reduce wound margins and encourage uniform granulation of uneven wound surface. The skin graft was deferred pending definitive histology results for diagnosis. The histopathology results confirmed total tumour excision, and a skin graft was undertaken a week later (Fig. 5C). The skin graft complicated with severe over-granulation (Fig. 5D) for which small incisional biopsy was taken, which proved no recurrence. Conservative treatment was undertaken for a month, and the skin graft healed (Fig. 5E).
Grossly, a 180 × 140 × 40 mm ulcerated and multi-lobulated tumour was received. On cut section, it was white-tan and firm. The hematoxy-eosin (H/E) stained sections showed ulcerated invasive sebaceous carcinoma evidenced by ulcerated skin with an invasive basaloid tumour (Fig. 6A) with sebaceous differentiated (Fig. 6B). The tumour cells were positive for epithelial membrane antigen (EMA) and p63 (some of basaloid cells) while B-cell lymphoma 2 (Bcl-2) and carcinoembryonic antigen (CEA) were negative. Excision was completed.

Discussion
Sebaceous carcinoma is an uncommon aggressive adnexal tumour. The great majority of SCs (75 %) occur in the periocular area, commonly, the eyelid [5]. Extraocular tumours account for only 25 % of sebaceous tumours [5]. The tumours occur sporadically or in association with Muir-Torre syndrome (MTS). MTS is a rare genetic condition that predisposes individuals to skin and visceral malignancies [6]. MTS is an autosomal dominant inheritance disorder. The risk factors for development of SCs include: age, Asian ethnicity, history of radiation on the head and neck, MTS and immusupression [7]. The other possible factors included in the literature are the use of the diuretics and infection by Human Papillomavirus (HPV) [7]. The loss of control of immune system to an oncogenic virus in HIV patient is a risk for development of SCs [8]. Nonetheless, one cannot deny the relevance of HIV-induced immunosuppression in the aetiology of these neoplasms [8]. Most of the literature indicates that SCs has female predominance and it commonly occurs at age range of 45-72 years [5]. A varied morphologic spectrum includes: basaloid, squamoid, organoid and neuro-endocrine [6]. This variable morphology poses a diagnostic dilemma in most cases [6].
The morphological subtype in this case report is basaloid. This SC subtype can mimic different types of neoplasms, which makes correct diagnosis a challenge [9]. The morphologic variation occurs more in extraocular than ocular sebaceous carcinoma. Pathogenesis of SC is unknown, but is thought to be due to inactivation of the cell cycle mediator tumour protein 21(P21) [2].
The clinical presentation is not a pathognomonic and is often non-specific. The tumour is usually firm; slow enlarging, yellowish to red-brown plaque, friable, crusted and often ulcerated. The size of extraocular tumour varies, with ranges of 6−10 cm on its greatest dimension. Judged against studies prior to this one, this tumour is the largest with the size of 180 × 140 × 30 mm to be reported.
The definitive diagnosis of this tumor is by histology results. The presence of sebocytes characterized by multi-vacuolated cytoplasm and pleomorphic nuclei suggests the diagnosis of SCs on microscopy [6]. However, immunostains are needed to confirm diagnosis because of the variations. EMA stain shows sebaceous differentiation [6].
Adjunct investigations include the CXR, CT-scan and MRI, as done in this case report. The MRI is an important modality not only for diagnosis, but also for planning of surgery. It gives adequate information about location, size and extent of invasion of adjacent structures by the tumour. Surgical excision with wide margins is the standard treatment [3]. In case of regional lymph node or distant metastases, radiotherapy used alone or with chemotherapy may reduce morbidity [3].
On both physical examination and radiological investigations, the patient did not have regional lymph node involvement. This implies a better diagnosis. The rate of metastasis in sebaceous tumour is about 14-25 %, which is similar for both extraocular and ocular types [6]. The nodal involvement is approximately 8-12 % [3]. The local recurrence is about 9-36 % post-operatively [3]. This patient was followed up for four months with no signs of recurrence; however, one should be aware that recurrence has even been reported after five years; hence, follow-up is vitally important.

Conclusion
Sebaceous carcinoma is a rare but aggressive tumour, which is notorious for mimicking other tumours. The earlier the diagnosis, the better the prognosis. In the case of this tumour, histological analysis is the gold standard for diagnosis. Surgical excision with wide margin is standard treatment. A recurrence is uncommon, hence follow-up is mandatory.

Funding
None.

Ethical approval
Sefako Makgatho University Research Ethics Committee (SMUREC) approved the publication of this case report.

Consent
Written informed consent to publish this case report and images was obtained from the patient. The copy of written informed consent will be available for Editor-in-Chief on request.

Author contribution
Dr. Sekgololo J.M. wrote the case report. Prof Chauke R.F. and Dr. Tshazi N., both critically revised the case report.

Registration of research studies
Not applicable, because is a single case report.

Provenance and peer review
Not commissioned, externally peer-reviewed.

Declaration of Competing Interest
None.