Extra ocular sebaceous carcinoma of the thigh: A case report.

CONTEXT: Sebaceous cell carcinoma is a malignant neoplasm, rarely recognized in extra ocular sites. His prognosis depends of the precocity of the diagnosis. This neoplasm is aggressive in 29%; lymph node and visceral metastasis aren't rare. CASE REPORT: An 80-year-old male had an ulcerated and infected nodule located on the left thigh. The lesion appeared after five months ago. It suspected a squamous cell carcinoma. The histologic findings revealed an extra ocular sebaceous carcinoma. The patient died one month later due to heart insufficiency.
CONCLUSION: extra ocular sebaceous carcinoma is a rare neoplasm. It has more difficulties of diagnosis because it has diverse clinical presentations as well as a variety of histologic patterns. We will discuss the incidence, clinical, histological and the prognosis of this aggressive neoplasm.

Introduction

Sebaceous cell carcinoma (SCC) is a rare malignant neoplasm that originates from cells comprises sebaceous glands[1]. It appears more frequently in the peri orbital region because there is an unusual abundance of sebaceous glands in the ocular region[2]. It can exhibit aggressive local behavior and can metastasize to regional lymph nodes and distant organs. Extra-ocular sebaceous carcinoma is very rare[3]. We report a new case of an extra ocular sebaceous carcinoma of the thigh and discuss the clinico-pathological features and the prognosis of this entity.

Case Report

We report a case of an 80-year-old man who presented with an ulcerated and infected nodule in the left thigh (Fig. 1) of five months duration. The rest of the physical examination was normal. particularly there's no lymph node metastasis. Diagnosis of squamous poorly differentiated carcinoma was performed on biopsy, and the patient underwent a large excision of the nodule.

Fig. 1

Photograph of the left thigh: an ulcerated and infected nodule.

Macroscopic examination showed a 23 × 17 × 8 cm ulcerated and infected nodule with macroscopically tumor free margin. Histologic examination revealed an intradermic proliferation of atypical enlarged basaloid and epithelioid cells, intermixed with focal mature sebocytes (Fig. 2a, 2b). Cytological atypia and mitotic activity were remarkable with focal necrosis (Fig. 3). The tumor infiltrated the hypoderm, it had an infiltrative border. Tumor cells were immunoreactive for cytokeratin 7 (Fig. 4).

Fig. 2

a: Tumor shows a mixture of atypical enlarged basaloid, epithelioid cells (HE × 100). 2: b: Sebaceous differentiation (HE × 200).

Fig. 3

Cytological atypia and mitotic activity were remarkable (HE × 400).

Fig. 4

Immunoreactive positivity for CK7 (IHC × 400).

The diagnostic of sebaceous carcinoma of the left thigh in his mixed and moderately differentiated type was performed. Imaging exploration showed multiples osseous metastases, revealed by bone gammagraphy (scintigraphy). The patient has not received any adjuvant therapy. He died one month later due to heart insufficiency.

Discussion

SCC accounts for less than 1 percent of all cutaneous malignancies, is a rare, but aggressive, malignant neoplasm that originates from sebaceous glands. It's more common in ocular adnexa, particularly in Asian countries[1]. SCC is a potential marker of Torre-Muir syndrome (MTS), alerting to search for an occult internal malignancy, most commonly colorectal carcinoma[4]. The MTS is defined by the combination of a sebaceous gland tumor and at least one visceral carcinoma occurring in the same individual in the absence of other precipitating factors. Skin lesions may precede the presentation of internal malignancies, but often develop later. In our case, there is no internal malignancy and it's considered to be an isolated case. Extra ocular sebaceous carcinoma is rare, which constitutes 25% of all cases of sebaceous carcinoma[5]. Most extra ocular SCC (75%) are encountered in the skin of the head and neck[5], followed by the trunk, salivary glands, genitals, and extremities[25].

In our case, the tumor affects the left thigh. It usually arises in adults, with an average patient age of 62 years and a slight male predominance[5]. Clinically, extra ocular sebaceous carcinoma was an erythaematous nodule that can sometimes ulcerate. In extraocular sites, sebaceous malignancies are commonly confused with basal cell carcinomas and squamous cell carcinomas with an exophytic/ulcerative lesion[23], like our case. Histological examination reveals a proliferation of atypical enlarged basaloid cells with focal mature sebaceous differentiation. Cytologic atypia and infiltrative border were usually noted. In contrast to peri ocular carcinoma, pagetoid intra-epithelial migration is uncommon[5].

SCC has more difficulties of diagnosis because it has diverse histologic patterns. It can be confused with other cutaneous tumors. SCC must be distinguished from basal cell carcinoma, amelanotic melanoma, squamous cell carcinoma and rarely metastatic clear cell carcinoma of the kidney. Tumor cells in sebaceous carcinoma were positive for cytokeratin 7, which usually absent in basal cell carcinoma. Melanotic cells tumor were positive for melan A and S100 protein contrary to sebaceous carcinoma[6].

Wide excision and selective use of radiotherapy remain the treatment of choice[27]. Sebaceous carcinoma can exhibit aggressive local behavior and metastasize to regional lymph nodes and distant organs[13]. It seems that extra ocular SCC has a poor prognosis than peri ocular form, but other studies have indicated that the pattern of metastasis and mortality are similar[89].

In summary, SCC is a rare and aggressive malignancy. This tumor should suggest the possibility of MTS and alert to search an occult internal malignancy.