Sebaceous carcinoma has been defined by the WHO as “a malignant tumor composed of sebaceous cells of varying maturity that are arranged in sheets and/or nests with different degrees of pleomorphism, nuclear atypia, and invasiveness” [
Sebaceous carcinoma is an aggressive, uncommon, cutaneous tumor first described by Allaire in 1891. This tumor is thought to arise from sebaceous glands in the skin and thus may arise anywhere on the body where these glands exist [
A 40-year female reported with a swelling on the right side, involving the middle third of the face, since 1 year. The swelling was firm in consistency, nontender, and of approximately 5 × 4 cm, extending superoinferiorly from the infraorbital ridge to 2 cm above the inferior border of the mandible and anteroposteriorly from the right corner of the mouth to 1.5 cm anterior to the tragus (Figure
(a) Clinical and (b) intraoral picture showing an intact buccal mucosa. (c) Water’s view radiograph of the patient. (d) Gross incisional tissue.
Microscopically, the tumor mass appeared to be located in the deeper mucosa with pushing margins of tumor nests (Figure
Pattern of asymmetry, a lack of circumscription with pushing or locally infiltrating margins (H and E stain; original magnification, 4x).
Large nests or lobules of neoplastic cells with squamous appearance, separated by scant stroma (H and E stain; original magnification, 10x).
Neoplastic cells had large vesicular nuclei with prominent nucleoli. Cellular and nuclear pleomorphism with few nuclei showing multilobation. Scattered typical and atypical mitotic figures seen (H and E stain; original magnification, 20x).
Sheets of multivacuolated/vesiculated cells having squamoid appearance, multilobation of some nuclei, high mitotic rate with abnormal mitosis (H and E stain; original magnification, 100x).
Photomicrograph showing lobules composed of clear tumor cells with foamy cytoplasm exhibiting absence of any mucin on PAS stain. (a) H and E stain; original magnification, 10x. (b) PAS stain; original magnification, 40x.
Variable number of smaller, darkly staining basaloid cells with oval-shaped nuclei and scant cytoplasm (H and E stain; original magnification, 40X).
The diagnosis of oral sebaceous carcinoma, “a benign-appearing” malignant neoplasm, remains challenging both clinically and histopathologically. Any anatomic site that contains sebaceous glands may potentially give rise to neoplasms exhibiting sebaceous differentiation. Fordyce’s spots represent ectopic sebaceous glands in the oral cavity and are commonly found in the buccal mucosa, upper lip, retromolar trigone, anterior tonsillar pillar, soft palate, and gingiva [
Clinical findings of reported cases of intraoral sebaceous carcinoma.
Reference | Age/sex | Anatomic site | Size (cm) | |
---|---|---|---|---|
1. | Damm et al. [ |
53/M | Left buccal mucosa | 3 |
2. | Abuzeid et al. [ |
11/F | Left buccal mucosa | 3 |
3. | Liu et al. [ |
68/M | Right buccal mucosa | 2.5 |
4. | Li et al. [ |
78/M | Left buccal mucosa | 3.5 |
5. | Handschel et al. [ |
80/F | Anterior floor of the mouth | 1.5 |
6. | Alawi and Siddiqui [ |
66/M | Left upper labial mucosa | 1.5 |
7. | Gomes et al. [ |
55/M | Right floor of the mouth | Not known |
8. | Wang et al. [ |
50/M | Left buccal mucosa | 4.6 |
9. | Oshiro et al. [ |
66/M | Dorsum of tongue | 2.5 |
10. | Rowe et al. [ |
76/M | Gingival mucosa, with metastasis to the lung and subcutis | 3 |
11. | Present case (2017) | 40/F | Right buccal mucosa | 5 |
The origin of sebaceous carcinoma in the oral cavity is still unclear. It may arise from intraoral minor salivary glands, parotid duct, or Fordyce granules [
Histologically, sebaceous carcinoma shows quite a range of differentiation, ranging from obviously multivacuolated epithelium to basaloid or squamoid populations of cells with more occult cytoplasmic lipid content [
According to Plaza et al. [
Diagnostic algorithm depicting the use of immunohistochemistry (IHC) to logically arrive to the diagnosis of sebaceous carcinoma (SC).
We did not perform IHC in our case because the diagnosis was quite obvious. Periodic acid-Schiff (PAS) stain was negative, confirming that the vacuolated clear cells were neither mucus cells nor glycogen-rich squamous cells, thus ruling out the possibility of a carcinoma arising from oral epithelium or salivary epithelium. Moreover, clear cell squamous cell carcinoma is characterized by areas of squamous differentiation with foci of keratinization and keratin pearls, which were absent in our case. In addition, basaloid squamous cell carcinoma was also excluded due to the absence of comedonecrosis, hyalinization of the stroma, or microcyst formation.
Furthermore, we observed a variable number of smaller, darkly staining, basaloid cells with oval-shaped nuclei and prominent nucleoli. These cells are thought to represent undifferentiated sebaceous cells [
In the current case, due to the presence of large nests of polygonal tumor cells with an optically clear cytoplasm, metastatic clear cell renal carcinoma was also thought as one of the differential diagnoses. This tumor is characterized by tumor cells arranged in nests and separated from each other by extensive rich network of delicate sinusoidal vascular channels. The tumor cells are generally large and polygonal, having a distinct cell membrane as if drawn by a “pencil” and an optically clear cytoplasm. This clear appearance of the cytoplasm of clear cell renal carcinoma is due to the presence of abundant glycogen and neutral lipids but not mucin [
Besides, benign tumors, including sebaceous adenoma, could not be considered in the histological differential diagnosis due to the infiltrative pattern and cytological features associated with sebaceous carcinoma. The presence of foci of cells with cytoplasmic microvacuoles and atypical scalloped nuclei confirmed the diagnosis of sebaceous carcinoma and ruled out the abovesaid malignant neoplasms.
The treatment of choice for sebaceous carcinoma is surgery, with complete excision verified by negative margins. Radiotherapy is used if metastatic disease and/or a high risk of recurrence are present. Multiagent chemotherapy has been used to treat recurrent disease [
Sebaceous carcinoma is a very aggressive, rare tumor which is generally not considered in the differential diagnosis of tumors arising from a site such as the buccal mucosa. This often leads to a delay in treatment. We emphasize the need to generate awareness about this rare entity occurring at unusual sites to expedite the patient’s survival.
The authors declare that they have no conflicts of interest.